MEDICAL MANAGEMENT OF ADULT CONGENITAL HEART DISEASE

Cyanotic

Cyanotic congenital heart disease can be viewed as a multisystem, systemic disorder that affects red blood cells and hemostasis, the kidneys, urate metabolism, the digits and long bones, bilirubin kinetics, respiration and ventilation, the coronary and systemic vascular beds, and the central nervous system.135

REGULATION OF RED CELL MASS

Erythrocytosis is a physiologically appropriate response to a decrease in tissue oxygenation (arterial hypoxemia) that stimulates elaboration of erythropoietin from specialized sensor cells in the kidney, resulting in an increase in the number of circulating red blood cells and in an expanded blood volume.136,137 The increase in erythrocyte mass offsets the deficit in tissue oxygenation. When erythrocytosis is sufficient to raise the tissue oxygen concentration above the threshold for release of erythropoietin by the renal oxygen sensors, a new equilibrium is established at a higher hematocrit level.138 Should tissue oxygen concentration fail to reach that threshold, or should the renal oxygen sensors fail to respond appropriately, a stable equilibrium at a higher hematocrit level is not achieved.138 Erythropoietin secretion and red blood cell mass continue to rise (negative feedback inhibition does not seem to occur) despite potentially harmful effects that accompany a further increase in hematocrit level.138

The adaptive increase in red blood cell mass of cyanotic congenital heart disease is fundamentally different from polycythemia rubra vera (primary polycythemia), which is an idiopathic clonal disorder of the bone marrow characterized by autonomous overproduction of red blood cells, thrombocytosis, leukocytosis, an increase in leukocyte alkaline phosphatase, and basophilia (see Chap. 57 ). To make that distinction clear, the increase in red blood cell mass prompted by the hypoxemia of cyanotic congenital heart disease is properly called “erythrocytosis” rather than “polycythemia.”135

The erythrocytosis of cyanotic congenital heart disease falls into two categories: compensated and decompensated, defined in terms of erythrocyte indices and hyperviscosity symptoms.138,139 Compensated erythrocytosis refers to patients who establish equilibrium hematocrit levels in iron-replete states and who have absent, mild, or moderate hyperviscosity symptoms, even at high hematocrit levels, even in excess of 70 per cent. Decompensated erythrocytosis refers to patients who fail to establish equilibrium conditions, who manifest unstable, rising hematocrit levels that are uncontrolled by negative feedback inhibition and who experience marked-to-severe hyperviscosity symptoms. Hematocrit levels should be determined by automated techniques, because microhematocrit centrifugation results in plasma trapping and falsely elevated levels.135

IRON AND IRON DEFICIENCY

IRON AND IRON DEFICIENCY. The role of iron and the effects of iron deficiency are important clinical aspects of the erythrocytosis of cyanotic congenital heart disease. Iron is an integral part of myoglobin and of certain mitochondrial enzymes and plays a pivotal role in oxidative metabolism. Iron deficiency decreases work capacity in both experimental animals and in human subjects.140,141 The consequences of iron deficiency are related not only to anemia per se but also to a decrease in the activity or concentration of iron-containing enzymes in muscle mitochondria and to impaired red cell deformability.135,140 During iron repletion, muscle oxidases approach control values, reflecting a shift to greater dependence upon oxidative metabolism. An important effect of iron deficiency is on red blood cell shape.140

Whole-blood viscosity is a function of hematocrit level and of a number of other variables including deformability of erythrocytes, aggregation and dispersion of cellular elements, flow velocity (shear rate), temperature, vessel bore, endothelial integrity, and plasma viscosity. The normal biconcave disc-shaped erythrocyte is a flexible membrane partially filled with a viscous, noncompressible hemoglobin solution that allows deformation into an infinite variety of shapes with little or no change in cell volume or surface area. Conversely, iron-deficient red blood cells are relatively rigid microspherocytes that resist deformation in the microcirculation, thus increasing whole-blood viscosity. Accordingly, for an equivalent red blood cell mass, whole-blood viscosity is higher in an iron-deficient state.140

PHLEBOTOMIES

PHLEBOTOMIES. Adults with cyanotic congenital heart disease and erythrocytosis are frequently phlebotomized and occasionally anticoagulated. The rationale for phlebotomy assumes an inherent increase in the risk of cerebral arterial thrombotic stroke, a risk that has not withstood scrutiny in a study of 112 adults with cyanotic congenital heart disease observed for a total of 748 patient years.142

In cyanotic adults, cerebrovascular accidents are often associated with excessive, injudicious phlebotomies or with the use of antiplatelet agents (aspirin) or anticoagulants that reinforce intrinsic hemostatic defects and risk intracranial bleeding.134,142 As the risk of stroke due to cerebral arterial thrombosis has not materialized, because the circulatory effects of phlebotomy are transient and because the result of phlebotomy-induced iron deficiency is an increase in whole-blood viscosity, phlebotomy is not recommended on the basis of hematocrit level per se.134,142 For patients with compensated erythrocytosis, phlebotomy is not advised, even when the hematocrit level exceeds 70 per cent, as long as symptoms attributed to hyperviscosity are absent, mild, or moderate. Hyperviscosity symptoms at hematocrit levels less than 65 per cent are almost always due to iron deficiency. Phlebotomy further depletes iron stores and aggravates rather than alleviates the symptoms that respond instead to iron repletion. Iron therapy must be monitored closely, because hematocrit levels tend to rise rapidly.134

The firmest indication for phlebotomy is marked-to-severe symptomatic hyperviscosity in patients with hematocrit levels exceeding 65 per cent, provided that dehydration is not the cause. The objective of phlebotomy is temporary alleviation of intrusive hyperviscosity symptoms while minimizing the degree of phlebotomy-induced iron deficiency. A comparatively simple and safe outpatient method of phlebotomy for adults involves removal of 500 ml of blood over 30 to 45 minutes followed by quantitative replacement of the volume with isotonic saline. Saline is as efficacious as albumin for volume replacement, but if saline is clinically undesirable, isovolumetric repletion can be achieved with dextran 40 (5 per cent dextrose in water), which is salt free.

HEMOSTASIS

HEMOSTASIS. Bleeding tendencies tend to be mild to moderate in cyanotic adults, and are principally mucocutaneous.143 However, epistaxis and hemoptysis vary from occasional and mild to copious and recurrent. In addition, serious and sometimes fatal bleeding can occur with accidental trauma or with surgical procedures. A decrease or absence of high molecular weight forms of the von Willebrand factor in plasma has recently been established and correlated with cyanosis, pulmonary vascular disease, and turbulent blood flow.143 The von Willebrand abnormality in congenital heart disease is believed to be acquired, and the types and prevalence of bleeding are similar to the patterns in other forms of acquired von Willebrand disease.143 Platelet counts are generally in the low range of normal in cyanotic adults but occasionally are moderately to markedly reduced.134

The hemostatic defect(s), especially in cyanotic patients, tend to be reinforced by an increase in tissue vascularity.143 Aspirin, oral anticoagulants, and nonsteroidal antiinflammatory agents increase these intrinsic bleeding tendencies. Bronchoscopy should not be used to investigate hemoptysis, because the procedure is accompanied by risks while providing no additional basis for therapeutic judgment.

Hematocrit levels above 65 per cent incur an increased likelihood of perioperative hemorrhage. Preoperative phlebotomy designed to reduce the hematocrit level to just below 65 per cent serves to improve hemostasis and decrease the perioperative risk.134 Phlebotomized units should be stored for potential postoperative autologous transfusion.

Another therapeutic issue in cyanotic adults is the use of nasal oxygen. From both the hematological and respiratory points of view, there is little evidence that oxygen is beneficial,144 and the drying effect on nasal mucous membranes increases the risk of epistaxis.

RENAL INVOLVEMENT

RENAL INVOLVEMENT. Involvement of the kidneys in cyanotic congenital heart disease has been known for over four decades, but the pathogenesis of the lesion has only recently been clarified.145 Renal histopathology resides chiefly in the glomerulus.146 The abnormality takes the form of a vascular response including dilatation of hilar arterioles, dilatation and engorgement of capillaries and enlargement of the glomerular tuft, and also a nonvascular response characterized by an increase in mesangial matrix and cellularity, and an increase in endothelial cell proliferation.145 The vascular response has been ascribed to release of L-arginine–derived nitric oxide that acts as an autocrine hormone, modulating the increased glomerular vascular resistance incurred by erythrocytosis.145 The nonvascular response has been assigned to local release of platelet-derived growth factor from the cytoplasm of circulating systemic venous megakaryocytes that are delivered into the systemic arterial circulation through the right-to-left shunt.145

URATE METABOLISM

URATE METABOLISM. Hyperuricemia and proteinuria are common features of cyanotic congenital heart disease.147 The mechanism of proteinuria is unclear, but a relationship appears to exist between proteinuria and hyperviscosity.147 High plasma uric acid levels are secondary to inappropriately low renal fractional uric acid excretion rather than to urate overproduction.147 Hyperuricemia therefore serves as a marker of abnormal intrarenal hemodynamics but appears to exert little or no deleterious effect on renal function and is not routinely treated.134 Acute gouty arthritis is relatively uncommon, despite elevated uric acid levels, an observation similar to that in other forms of secondary hyperuricemia.147,148

Intravenous colchicine, the preferred treatment for acute gouty arthritis in cyanotic adults, is followed by a rapid clinical response and minimizes the undesirable dehydrating gastrointestinal side effects of oral colchicine. Prophylaxis after resolution of acute gouty arthritis is best achieved with low-dose oral colchicine (0.6 mg once or twice daily), a dose schedule that prevents recurrences in 75 to 90 per cent of patients and is usually tolerated without gastrointestinal side effects. Recurrent gouty arthritis is treated with allopurinol, probenicid, sulfinpyrazone, or combined therapy.

CLUBBING OF THE DIGITS AND HYPERTROPHIC OSTEOARTHROPATHY

CLUBBING OF THE DIGITS AND HYPERTROPHIC OSTEOARTHROPATHY (Fig. 2–4 Fig. 2–4 ). These abnormalities are also believed to be responses to local release of platelet-derived growth factor from the cytoplasm of megakaryotyes that are shunted from right to left and that impact in the capillary beds of the fingers, toes, and periosteum.149 Clubbing is asymptomatic, but hypertrophic osteoarthropathy not uncommonly causes arthralgias over long bones. If therapy is indicated, salsalate is sometimes helpful. The drug is a nonacetylated analog of aspirin but does not interfere with normal platelet function.

GALLSTONES

GALLSTONES. Cyanotic adults with erythrocytosis are at risk for cholelithiasis caused by calcium bilirubinate gallstones134 (Fig. 30–12A Fig. 30–12A ). An expanded red blood cell mass provides the substrate for an increase in unconjugated bilirubin, which is believed to cause pigment stones because the compound is largely insoluble in water. Biliary colic may become clinically overt years after surgical relief of the cyanosis. An additional hazard of acute cholecystitis is infective endocarditis caused by bacteremia associated with septic inflammation of the gallbladder (Fig. 30–12B Fig. 30–12B ).

OXYGEN UPTAKE AND CONTROL OF VENTILATION

OXYGEN UPTAKE AND CONTROL OF VENTILATION. Diversion of venous blood into the systemic arterial circulation is a basic pathological fault in cyanotic congenital heart disease. Exercise serves to increase significantly the degree of venoarterial shunting and materially influences the dynamics of oxygen uptake (VO2) and ventilation.150,151 Patients with cyanotic congenital heart disease experience markedly abnormal responses in achieving a steady state for VO2 after the onset of dynamic (isotonic) exercise. The prolonged onset and recovery of VO2 kinetics result in large O2 deficits and hypoxemia, even with low levels of isotonic exercise; this suggests that patients with significant right-to-left shunts rely to an unusual degree on anaerobic metabolism. Unlike in the prolonged VO kinetics, cyanotic patients exhibit large increases in ventilation in phase I of exercise, and, in contrast to normal subjects, ventilation increases much more rapidly than VO2 in phase II (Fig. 30–13 Fig. 30–13 ).150,151 Ventilatory stimuli that are augmented by exercise in patients with right-to-left shunts include hypoxemia, metabolic acidosis, and shunting of CO2 into the systemic arterial circulation. Because these patients have a substantially greater increase in ventilation during isotonic exercise than do normal subjects, “dyspnea” may be a prominent subjective complaint.134 The New York Heart Association functional class is inappropriate because “dyspnea” is, in fact, hyperventilation unrelated to heart failure. The functional classification shown in Table 30–1 Table 30–1 is recommended for patients with congenital heart disease.

THE CORONARY VASCULAR BED

THE CORONARY VASCULAR BED. It has long been known that the extramural coronary arteries in older patients with cyanotic congenital heart disease tend to become enlarged and tortuous, sometimes dramatically so.152 The reason may lie in the dilating effects of nitric oxide and perhaps of prostaglandins that are elaborated by endothelium in response to the viscosity-induced increase in shear stress.143 Of potentially greater functional importance is the effect of cyanotic congenital heart disease on myocardial perfusion. Recent studies using positron emission tomography (PET) disclosed that myocardial perfusion at rest is normal, but perfusion reserve is reduced after pharmacological stress, implying a perfusion deficit during physical exercise.153

DISORDERS OF THE CENTRAL NERVOUS SYSTEM

DISORDERS OF THE CENTRAL NERVOUS SYSTEM. Prominent among these in adults with congenital heart disease are brain abscess, cerebral emboli, subclavian steal, syncope, intracerebral and subarachnoid hemorrhage, and seizures.154

The pathogenesis of a brain abscess is not always clear. Right-to-left shunts in patients with cyanotic congenital heart disease bypass the pulmonary filter, permitting bacteria to enter the systemic and therefore cerebral circulations. However, a focal zone of cerebral vulnerability appears to be necessary for formation of abscess.154 Brain abscess should be suspected when adults with cyanosis experience headache, focal neurological signs, seizures, and fever. The diagnosis of a recent brain abscess can be established by computed tomography (CT), which identifies the lesion and the distinctive ring enhancement. Seizures may accompany the fresh abscess and may persist or recur years later because of focal brain injury at the site of the healed abscess.

Paradoxical Emboli

Paradoxical Emboli. Cerebral emboli (see [For More Information] ) can be bland or infected. Relatively unique to congenital heart disease—usually, but not necessarily, cyanotic—are para-doxical emboli.154 In cyanotic patients, paradoxical emboli originate in lower-extremity or pelvic veins and reach the brain by peripheral venous blood that has direct access to the systemic arterial circulation due to the right-to-left shunt. Anticoagulants may reduce the risk of paradoxical embolization, but reinforce the intrinsic hemostatic defects in cyanotic patients and increase the risk of cerebral hemorrhage.

A potential source of paradoxical embolization in hospitalized cyanotic patients is an intravenous line inserted for infusions or drugs.155 Particles or air accidentally introduced into peripheral veins may be delivered into the systemic circulation through the right-to-left shunt.

Paradoxical emboli in acyanotic patients occur when an interatrial communication—ostium secundum atrial septal defect or patent foramen ovale—permits inferior caval blood to stream across the atrial septum into the left atrium and systemic circulation. Recent interest has focused upon young adults with stroke ascribed to paradoxical emboli through a patent foramen ovale,156 a pathway analogous to that of an ostium secundum atrial septal defect. Platelet/ fibrin particles that circulate in the systemic nervous bed are removed by the efficient lytic system in the lungs. Isometric exercise, the Valsalva maneuver, or vigorous coughing may provoke transient venoarterial mixing that delivers clusters of these particles through a patent foramen ovale into the systemic circulation and into a cerebrovascular bed that lacks a lytic system. The Valsalva maneuver is used diagnostically to initiate a transient right-to-left shunt through a foramen ovale during contrast echocardiography or transcranial contrast ultrasound.156

An atrial septal aneurysm may be the source of fibrin/platelet thrombi and embolic strokes, generally manifested by transient ischemic attacks in acyanotic patients.157 The aneurysm can be suspected in a transthoracic echocardiogram but is best established by transesophageal echocardiography (see Fig. 3–16 Fig. 3–16 ).

Cerebral Hemorrhage

Cerebral Hemorrhage. This complication tends to occur in adults with congenital heart disease under a limited number of circumstances. One cause is the injudicious use of anticoagulants or antiplatelet agents in cyanotic patients. An uncommon but potentially catastrophic cause of a hemorrhagic cerebrovascular accident is rupture of a congenital aneurysm of the circle of Willis, especially but not exclusively in patients with coarctation of the aorta (Fig. 30–3 Fig. 30–3 ).

Mycotic aneurysms (better termed septic aneurysms) (Fig. 30–14 Fig. 30–14 ) result from inflammatory weakening of the wall of a cerebral artery caused by septic microemboli to vasa vasora or by impaction of an infected embolus in the lumen of the artery.154 Cerebral mycotic aneurysms may enlarge and rupture despite antibiotic eradication of the offending organism. Headaches or seizures announce an enlarging or perforating aneurysm, which can be diagnosed by CT scan and cerebral angiography. Aneurysms approaching 1 cm in diameter are treated by surgical excision to prevent catastrophic rupture.

Other Neurological Complications

Other Neurological Complications. The subclavian steal is an occasional neurological complication of a Blalock-Taussig anastomosis.158 The classic shunt operation may create an anatomical and physiological substrate analogous to that of an atherosclerotic subclavian steal. Symptoms of the steal may appear decades after the shunt is established, depending on the development of cervical and intrathoracic collaterals. The steal is not necessarily corrected by intracardiac repair, even though the anastomosis is ligated. Congenital subclavian steal is rare.

In patients with congenital aortic stenosis, cerebral symptoms may consist of mere giddiness, faintness, or lightheadedness with effort. Conversely, syncopal episodes are sometimes recurrent and potentially dangerous.

Infective Endocarditis: Risks and Prophylaxis

(See also Chap. 33 )

The clinical and bacteriological profiles of infective endocarditis changed significantly after the advent of cardiac surgery and prosthetic devices. Certain operations (division of a patent ductus arteriosus) eliminate the risk, whereas other operations (shunts, prosthetic valves or conduits) materially increase the risk.2 However, certain general principles still prevail: namely, that the two major predisposing factors that increase the risk of infective endocarditis are a susceptible cardiac or vascular substrate and the presence of bacteremia. Susceptible lesions are those associated with high-velocity turbulent flow, jet impact, and focal increases in the rate of shear. An exception is the peculiar lack of susceptibility associated with the high-velocity diastolic flow accompanying pulmonary hypertensive pulmonary regurgitation. Portals of entry include the oral cavity, the genitourinary tract in men, the upper and lower gastrointestinal tracts, the airways and respiratory tract, and treatments such as obstetrical and gynecological procedures, and certain types of noncardiac surgery.

Susceptibility to infective endocarditis in congenital heart disease has been classified according to low-risk unoperated anomalies, low- or no-risk postoperative, intermediate-risk unoperated, intermediate-risk postoperative, and high-risk postoperative.2 Low-risk unoperated anomalies are represented by ostium secundum atrial septal defect and mild pulmonary valve stenosis. A no-risk postoperative lesion is typified by a patent ductus arteriosus after ligation. Intermediate-risk unoperated lesions are represented by a functionally normal bicuspid aortic valve, aortic regurgitation, restrictive ventricular septal defect, or patent ductus arteriosus, especially restrictive. Intermediate-risk postoperative lesions include bicuspid aortic stenosis and residual aortic or left atrioventricular valve regurgitation. High-risk postoperative substrates include rigid prosthetic valves (especially left-sided), external-valved conduits, and aortopulmonary shunts.

Prophylaxis for infective endocarditis consists of both nonchemotherapeutic and chemotherapeutic (antimicrobial) measures. Nonchemotherapeutic prophylaxis involves day-to-day oral hygiene, skin care, nail care, and female contraception. The spongy, fragile gums of patients with cyanotic congenital heart disease are of special concern. A soft-bristled toothbrush should be used. Dental appointments for prophylaxis should be at least twice yearly. Meticulous skin care is important, especially in adolescents and young adults with acne that may be distributed beyond the face. Biting or picking of fingernails risks injury to contiguous skin and predisposes to paronychial infection with staphylococci. Intrauterine devices are best avoided because of the risk of bacteremia.

Pregnancy and Congenital Heart Disease: The Mother and the Fetus

(See also [For More Information] )

Central to this topic is the intricate interplay between maternal circulatory and respiratory physiology and maternal congenital heart disease and the effects of this interplay upon the fetus. The fetus is exposed to risks that threaten its intrauterine viability and to risks that subsequently express themselves as developmental defects or transmitted congenital malformations of the heart or circulation.159

An important aspect of congenital heart disease and pregnancy is contraception.159 Barrier methods include the condom (male) and the diaphragm with spermicide for the female. Tubal ligation can be accomplished safely, even in relatively high-risk women. The levonorgestrel implant (controlled release of progestin) is a safe and efficacious contraceptive for cyanotic women with pulmonary vascular disease. Retention of fluid is modest and does not preclude use of the implant for patients with controlled heart failure. Progestin injections are not recommended for patients with heart failure because of the associated retention of fluid. Low estrin is the lowest estrogen-containing oral contraceptive, and is considered safe and nonthrombogenic with a low rate of failure if no dose is missed. Use of the intrauterine device within a monogamous relationship probably does not increase the risk of infection or of infective endocarditis, but endometrial irritation may induce excessive bleeding, especially in patients with cyanotic congenital heart disease and hemostatic defect(s).

THE UNOPERATED PATIENT

There are a number of common congenital malformations that are found in unoperated adult women (Table 30–2 Table 30–2 ).

OSTIUM SECUNDUM ATRIAL SEPTAL DEFECT

OSTIUM SECUNDUM ATRIAL SEPTAL DEFECT. This malformation is of special relevance because the history without operation spans the reproductive years and because the majority of affected patients are female.5 Young women with uncomplicated ostium secundum atrial septal defects generally tolerate pregnancy with no ill effects. An important risk, however, is a paradoxical embolus that originates in pelvic and leg veins and is carried by inferior vena caval blood across the atrial septal defect into the systemic circulation.160 Accordingly, meticulous leg care and early ambulation after delivery are mandatory. Acute blood loss poses a potential risk because hemorrhage provokes a rise in systemic vascular resistance and a fall in systemic venous return, augmenting the left-to-right shunt, sometimes appreciably.159

PATENT DUCTUS ARTERIOSUS

PATENT DUCTUS ARTERIOSUS. This anomaly predominates in women but is of limited practical importance as a complication of pregnancy, because the clinical diagnosis is simple, and division of the ductus in childhood is curative. A small or moderate-sized patent ductus with normal pulmonary arterial pressure poses no risk apart from susceptibility to infective endocarditis during delivery. In the presence of a moderately restrictive patent ductus (Fig. 30–15 Fig. 30–15 ), the gestational fall in systemic vascular resistance serves to decrease ductal flow, but if the shunt is large, that benefit is unlikely to compensate for the hemodynamic burden of pregnancy. At highest risk is the patient with a nonrestrictive patent ductus, pulmonary vascular disease, and reversed shunt.159 The gestational decline in systemic vascular resistance augments the right-to-left shunt through the ductus, further lowering uterine arterial oxygen saturation, which poses potential harm to the fetus.

ISOLATED PULMONARY VALVE STENOSIS

ISOLATED PULMONARY VALVE STENOSIS. Fifty per cent of patients with this malformation are women and adult survival is the rule, even in the presence of significant obstruction to right ventricular outflow.5 Severe pulmonary stenosis is occasionally tolerated despite gestational volume overload imposed upon an already pressure-loaded right ventricle. Infective endocarditis prophylaxis is advisable during delivery, although the probability of infection in patients with mild obstruction to right ventricular outflow is believed to be negligible.

COARCTATION OF THE AORTA

COARCTATION OF THE AORTA. The malformation occurs chiefly in men but is dealt with here because maternal morbidity—cardiovascular complications without death—is relatively high.159,161 The hypertension of coarctation is accompanied by a comparatively low incidence of toxemia compared to other forms of systemic hypertension.5 Connective tissue changes in the walls of systemic arteries during normal pregnancy162 increase the risk of aortic rupture or dissection, especially in the vulnerable postcoarctation segment and in the aortic root,20 and increase the risk of cerebral hemorrhage from rupture of an aneurysm of the circle of Willis (Fig. 30–3 Fig. 30–3 ). Left ventricular failure is exceptional, despite augmented volume imposed upon the pressure-loaded left ventricle. Susceptibility to infective endocarditis is determined chiefly by coexistence of a bicuspid aortic valve.

BICUSPID AORTIC STENOSIS

BICUSPID AORTIC STENOSIS. Because of the low incidence of this malformation among women, bicuspid aortic stenosis is only an occasional complication of pregnancy. The increased cardiac output tends to be tolerated in women with mild-to-moderate bicuspid aortic stenosis, but severe obstruction encroaches on limited circulatory reserve. Dyspnea, angina pectoris, or cerebral symptoms that precede conception or appear early in gestation are matters of grave concern.

BICUSPID AORTIC REGURGITATION

BICUSPID AORTIC REGURGITATION. Moderate-to-severe chronic bicuspid aortic regurgitation is generally well tolerated during pregnancy, provided that the adaptive response of the left ventricle preserves normal function. The gestational fall in systemic vascular resistance, together with a more rapid heart rate (shorter diastole), results in a decrease in regurgitant flow.159 The risk of infective endocarditis is high; therefore, antibiotic prophylaxis is obligatory during labor and delivery.

FALLOT’S TETRALOGY

FALLOT’S TETRALOGY. About half of patients with this anomaly are women, and Fallot’s tetralogy is the most common cyanotic malformation that might permit unoperated survival into reproductive age. A gestational fall in systemic vascular resistance and augmented venous return to an obstructed right ventricle result in an increase in the right-to-left shunt and a fall in systemic arterial oxygen saturation, changes that are especially harmful to the fetus. During labor and delivery, a sudden fall in systemic vascular resistance may precipitate intense cyanosis, syncope, and death. Conversely, bearing down during labor may abruptly and dangerously reduce systemic arterial blood flow.

CONGENITAL COMPLETE HEART BLOCK

CONGENITAL COMPLETE HEART BLOCK. This uncommon congenital conduction defect permits survival into childbearing age, and about one-half of the patients are female.5 Asymptomatic young women usually experience an uneventful pregnancy, provided that the QRS duration is not prolonged and the rate response to exercise is satisfactory.159,163,164 Stokes-Adams attacks occasionally occur during gestation, and the heart and circulation may not respond appropriately to the volatile demands of labor and delivery.

EBSTEIN’S ANOMALY OF THE TRICUSPID VALVE

EBSTEIN’S ANOMALY OF THE TRICUSPID VALVE. About half of the patients with this malformation are women, and the majority reach adulthood.5 The functionally inadequate right ventricle, already volume-overloaded by tricuspid regurgitation, copes poorly with the gestational increase in cardiac output.165 Atrial tachyarrhythmias occur in approximately one-third of nonpregnant patients with Ebstein’s anomaly and are potential hazards during pregnancy.166 Wolff-Parkinson-White bypass tracts set the stage for excessively rapid ventricular rates in response to atrial fibrillation or flutter (Fig. 30–7 Fig. 30–7 ). The consequences can be catastrophic. Cyanosis in Ebstein’s anomaly (right-to-left interatrial shunt) may first become manifested during pregnancy because of a rise in right ventricular filling pressure. The right-to-left shunt increases the risk of paradoxical embolization, and the hypoxemia increases the risk to the fetus.

THE POSTOPERATIVE PATIENT

There is a consensus that successful surgery before gestation can be pivotal in reducing maternal risks of congenital heart disease. Surgery should therefore be anticipatory. The objectives of reparative surgery are to increase the safety and success of pregnancy, to preserve the health of the mother, and to reduce the risk to the fetus. Closure of an ostium secundum atrial septal defect in children or young adults permits pregnancy without maternal risk. The complication of paradoxical embolization from the inferior vena cava is eliminated. However, an increase in incidence of atrial tachyarrhythmias should be considered when the defect is closed after young adulthood.

Division of a small nonpulmonary hypertensive patent ductus early in life is curative. Division of a nonrestrictive or moderately restrictive ductus is sometimes followed by incomplete resolution of elevated pulmonary vascular resistance or by less than adequate functional recovery of the volume-overloaded left ventricle, important residua that might confront the pregnant woman. In any event, division of a patent ductus eliminates the risk of infective endocarditis.

Successful response of congenital pulmonary valve stenosis to balloon dilatation or to direct repair permits the pregnant woman to anticipate a normal pregnancy except for a low, if not altogether absent, risk of infective endocarditis. Mild-to-moderate low-pressure postinterventional pulmonary regurgitation is not a concern, with few exceptions. Balloon dilatation has proven efficacious during pregnancy (Fig. 30–9 Fig. 30–9 ).

After repair of coarctation of the aorta, the risk of pregnancy depends on relief of the isthmic obstruction (and reduction of systemic blood pressure), the surgical technique, and whether or not a bicuspid aortic valve coexists. To what extent correction of coarctation reduces the hazard of gestational rupture of an aneurysm of the circle of Willis is open to question. The histology of the aorta immediately distal to the coarctation resembles that of cystic medionecrosis, and balloon dilatation injures this already vulnerable aortic segment.20 Relief of the isthmic obstruction by partial resection and roofing with a graft leaves the vulnerable postcoarctation aortic segment largely in place. The procedure of choice in women is resection that includes the segment of aorta distal to the coarctation, with end-to-end anastomosis. Should a bicuspid aortic valve coexist, two additional postoperative concerns persist: susceptibility to infective endocarditis and the risk inherent in the histological abnormalities of the aortic root.

Surgical relief or balloon dilatation of congenital bicuspid aortic stenosis (Fig. 30–10 Fig. 30–10 ) significantly lowers the risk of pregnancy (see earlier), but not the risk of infective endocarditis. In the presence of hemodynamically significant bicuspid aortic regurgitation, it is usually better to advise pregnancy before aortic valve replacement, provided that left ventricular function is normal or nearly normal. If a stenotic or incompetent aortic valve requires replacement in a woman of childbearing age, a tissue valve has the advantage of good hemodynamics without the need for anticoagulants (but with the caveats commented upon later).

Pregnancy after repair of Fallot’s tetralogy is accompanied by a gratifyingly small risk, especially when outflow obstruction is relieved without inducing significant low-pressure pulmonary regurgitation. Elimination of cyanosis increases the probability of successful conception,167 improves the stability of pregnancy, and results in normal fetal growth and development. Postoperative electrophysiological sequelae cannot be ignored but are comparatively infrequent when successful repair is accomplished at a young age (see [For More Information] ).

Closure of a nonrestrictive or moderately restrictive perimembranous ventricular septal defect in infancy or early childhood serves to preclude the development of pulmonary vascular disease and to relieve the left ventricle of volume overload. Pregnancy can be anticipated with optimism. Postoperative electrophysiological sequelae are exceptional.

A pacemaker is occasionally required in young women with congenital complete heart block, but with relative confidence that pregnancy can then safely proceed if ventricular function is normal, which is usually the case. Although a dual-chamber pacemaker is preferable, a fixed-rate system provides satisfactory physiological support.

Surgical repair of Ebstein’s anomaly of the tricuspid valve ideally takes the form of reconstruction using the large mobile anterior tricuspid leaflet to create a competent unicuspid atrioventricular valve. Active or potential bypass tracts are eliminated by surgical dissociation of right atrium from right ventricle (Fig. 30–7 Fig. 30–7 ). The maternal risk of pregnancy, including susceptibility to infective endocarditis, is reduced but not eliminated.

Pregnancy after repair of certain forms of complex cyanotic congenital heart disease is now a practical objective. However, menstrual patterns of women who were cyanotic before operation differ significantly from normal women, implying abnormalities of gynecological endocrinology that may influence fertility.167 After a Fontan procedure, a twofold increment in cardiac index can usually be achieved in response to isotonic exercise.168 The corollary is that women who have undergone successful Fontan repairs and have good if not normal ventricular function confront the physiological burden of pregnancy with circulations that potentially possess adequate hemodynamic reserve. However, other variables may influence outcome.133

Medical Management of the Pregnant Woman with Congenital Heart Disease

PRENATAL CARE

PRENATAL CARE. A major objective of medical management is to minimize the factors that encroach upon the limited circulatory reserve of pregnant women with heart disease. Cardiac reserve is encroached upon by the hemodynamic burden of pregnancy and by the heart disease itself. Anxiety is a special concern in the primigravida as she anticipates her first gestational experience. The expectant mother should be prepared for what awaits her during pregnancy, labor, delivery, and puerperium in order to decrease if not eliminate fear of the unknown. Diuretics can be used judiciously for the edema of cardiac failure but should not be used for the edema of normal pregnancy.159 The pregnant woman with heart disease should limit herself to moderate isotonic exercise. Heat and humidity add to the hemodynamic burden; a dry cool atmosphere is therapeutic. The physiological anemia of pregnancy must be distinguished from pathological anemia, and the latter assiduously addressed. Meticulous leg care reduces the gestational tendency for lower-extremity venous stasis and the attendant risk of thromboembolism. Passive standing should be avoided, the supine position minimized (compression of the inferior vena cava by the enlarged uterus), and the pregnant woman should minimize or avoid sitting with knees flexed and legs dependent. As term approaches, an important element in reducing anxiety is assurance that the pain of labor and delivery will be minimized.

The efficacy of oxygen administration during gestation in cyanotic women is open to question, with little or no convincing evidence of benefit to the mother. There is less-than-convincing evidence that oxygen administration exerts a favorable effect on growth retardation of the fetus in cyanotic women.

Maternal mortality in pregnant women with heart disease has been coupled with functional class. Symptoms associated with congenital heart disease, especially cyanotic, have prompted the use of the functional classification shown in Table 30–1 Table 30–1 . In addition to and apart from symptoms and functional limitations, certain congenital cardiac malformations impose such a formidable threat to maternal survival that pregnancy is proscribed or should be interrupted. Of the two major maternal cardiac risks—pulmonary vascular disease and pulmonary edema—the former is more relevant to congenital heart disease. Primary pulmonary hypertension epitomizes this risk (see Chap. 25 ), but pulmonary vascular disease in any context is a major hazard, limiting if not precluding rapid adaptive responses to the circulatory changes of pregnancy and to the volatile changes during labor, delivery, and the puerperium.

LABOR AND DELIVERY

LABOR AND DELIVERY. In women with functionally mild unoperated lesions and in patients after successful cardiac surgery, management of labor and delivery is the same as for normal pregnant women. The need for infective endocarditis prophylaxis during routine delivery in pregnant cardiac patients has been questioned because of the low incidence of bacteremia that accompanies a normal uncomplicated vaginal delivery.169 It should not be assumed, however, that a given delivery will be uncomplicated. An episiotomy and vacuum extraction are, strictly speaking, not “normal.” Accordingly, pregnant women with cardiac lesions susceptible to infective endocarditis should receive appropriate antibiotic prophylaxis from the onset of labor through the third or fourth postpartal day.170

For pregnant women with functionally important congenital cardiac disease—unoperated or operated—the management of labor, delivery, and the puerperium is crucial if risk is to be minimized. The first necessity is to underscore the beneficial effects of induced vaginal delivery. Cesarean section should be reserved for cephalopelvic disproportion, for breech presentation, or for preterm labor in a woman receiving coumadin anticoagulation. Cesarean section results in about twice the blood loss as vaginal delivery, in addition to the risks of wound and uterine infection, thrombophlebitis (delayed ambulation), and potential postoperative complications.

Amniocentesis around the 37th week determines whether or not fetal lung maturity has been achieved and whether induced delivery can safely proceed. The pregnant woman is then admitted for induction, with delivery planned as far as possible during the working day so that a high-risk obstetrician, neonatologist, and cardiologist can more readily be available. On admission, prostaglandin vaginal gel is applied to soften and dilate the cervix.159 Laminaria, derived from the stems of a special seaweed, can be used for the same purpose because of its hydrophilic properties. Oxytocin may be required for augmentation of uterine contractions that are usually initiated by absorbed prostaglandin. The sequence of cervical softening and dilatation precedes the onset of uterine contractions, as in normal spontaneous vaginal delivery.

After contractions are under way, artificial rupture of the membranes is performed. The woman should labor in a lateral decubitus position in order to attenuate the hemodynamic fluctuations provoked by major uterine contractions in the supine position. Meperidine is used selectively for relief of pain and apprehension. The anesthetic of choice is a lumbar epidural preparation, such as fentanyl, that exquisitely controls pain without reducing the strength of uterine contractions, which are monitored together with fetal rate (Fig. 30–9A Fig. 30–9A ). The fetus is allowed to pass through the pelvis in response to the force of uterine contractions unsupplemented by straining in order to avoid the undesirable circulatory effects of the Valsalva maneuver. Delivery is assisted by vacuum extraction and low forceps.

Systemic arterial pressure should be monitored during labor, because lumbar epidural anesthetics may cause hypotension. In patients with Fallot’s tetralogy or Eisenmenger’s complex, a sudden fall in systemic vascular resistance poses a special threat. Use of a flotation catheter for hemodynamic monitoring is an individual cardiological decision, rather than routine policy. In Eisenmenger’s complex, for example, the risks of a flotation catheter far outweigh the benefits.171 Oxygen is often intuitively administered during labor, especially in cyanotic women, although without proven efficacy.

After expulsion of the placenta, bleeding is reduced by uterine massage. If intravenous oxytocin is used, the drug should be administered slowly because of its potential hypotensive effect. In the postpartum period, meticulous leg care, use of elastic support stockings, and early ambulation are important preventive measures that reduce the risk of thromboembolism.

BREAST FEEDING

BREAST FEEDING. This practice may encroach upon cardiac reserve and increase the risk of mastitis and bacteremia. Nursing should therefore be advised with caution in patients with congenital cardiac disease, and its duration should be minimized. Engorgement of the breasts and suppression of lactation are managed with binding, cold packs, and analgesics rather than with bromocriptine, which can cause hypotension.

Medical Management of the Fetus

Maternal congenital heart disease exposes the fetus to risks that threaten its intrauterine viability and to risks of potential congenital and developmental malformations.172 Intrauterine viability is influenced by the functional class of the mother (with the qualifications noted above), by maternal cyanosis, and by oral anticoagulants. Maternal cyanosis threatens the growth, development, and viability of the fetus and materially increases fetal wastage, dysmaturity, and prematurity. The risk to the fetus of oral anticoagulants has not been satisfactorily resolved, so the need for anticoagulation should be minimized (see [For More Information] ). Valve reconstruction is recommended in women of childbearing age. A bioprosthetic valve obviates the need for anticoagulants but subjects the patient to subsequent reoperation. In addition, there is concern that pregnancy itself might accelerate degeneration of a bioprosthetic valve because of the inherent gestational changes in connective tissue. Aspirin is not a viable alternative to anticoagulants because of its potential for closing the fetal ductus and because of low efficacy.

There is no consensus on how best to administer anticoagulants. It is currently believed that the risk of fetal wastage from heparin is not of the same order as from coumadin,173 previous reports notwithstanding. Whichever regimen of heparin and/or coumadin is chosen, the patient and her partner should be so advised before conception. There is a mounting consensus that warfarin should be replaced with heparin before conception in order to avoid the teratogenic risk of coumadin in early gestation.

The change from coumadin to heparin is best accomplished in the hospital. A nurse specialist instructs the patient and her partner on the technique of subcutaneous administration of heparin using a short 25-gauge needle and an abdominal site for injection at right angles to the elevated skin surface. The needle should be withdrawn slowly, and the site should not be massaged.

Heparin can either be continued throughout gestation (provided that the anticoagulant response is carefully monitored) or replaced with warfarin in the second trimester, returning to heparin in the 36th week. Because of harmful effects that coumadin might exert on the fetal central nervous system—which continues to develop throughout gestation—it has been argued that heparin is the preferred drug because it does not cross the placental barrier and is therefore not teratogenic either during initial organogenesis or during subsequent maturation of the higher centers of the brain. That is, the risk of coumadin lies not only in warfarin embryopathy but potentially in the effect of the oral anticoagulant on central nervous system development.174 In light of concern that the risk of embryopathy varies directly with blood level, warfarin dosage should be monitored using the International Normalized Ratio (INR) in order to achieve a therapeutic range at the lowest possible dose.175

Preterm labor in a pregnant woman taking warfarin threatens the fetus with fatal hemorrhage because fetal anticoagulation cannot be promptly reversed. Emergency cesarean section is required if the fetus is to be saved. Maternal administration of vitamin K and infusion of fresh frozen plasma do not reverse fetal anticoagulation quickly enough to obviate fatal hemorrhage, but fresh frozen plasma should be administered to the newborn. There are, however, four concerns regarding the administration of heparin throughout pregnancy173: (1) greater difficulty in achieving a stable therapeutic response; (2) the inconvenience of parenteral administration, an inconvenience that the woman may not be prepared to sustain; (3) the risk of heparin-induced thrombocytopenia; and (4) the risk of bone demineralization.

Extracorporeal circulation is associated with a high incidence of fetal wastage, but cardiac surgery is rarely employed during gestation, especially in the pregnant woman with congenital heart disease. Should cardiac surgery be necessary, it is best to await the 25th to 26th week of gestation.

In addition to threats to its intrauterine viability, the fetus is exposed to risks that take the form of genetic parental transmission, teratogenic effects of certain cardiac drugs, and the harmful effects of certain environmental toxins. A substantial majority of congenital heart diseases cannot be attributed to either a syndrome or a single-gene defect that exhibits mendelian inheritance.172 A number of studies have concluded that the risk of recurrence of congenital cardiac defects in offspring is greater if the mother rather than the father is the affected parent.172 A hypothesis that might account for this pattern is cytoplasmic or maternal inheritance based on the observation that mitochondrial DNA is inherited only from the mother.172 A second hypothesis, “parental imprinting” or “genomic imprinting,” refers to gene expression that varies according to its maternal or paternal origin.176 The imprinting factor is believed to be DNA methylation.

Exercise Before and After Surgery or Interventional Catheterization

Certain types of congenital disorders of the heart or circulation expose patients to the risk of complications or sudden death during strenuous exercise or competitive sports.177 Consideration must be given to (1) the type, intensity, and duration of exercise; (2) the risk of body collision inherent in a given type of athletic activity; (3) the training program (conditioning) required for a given sport; (4) the emotional stress that the participant experiences in anticipation of or during a particular sport event; (5) the risk of injury to either the participant or spectators if the athletic activity induces loss of consciousness; and (6) the sometimes arbitrary distinction between competitive and recreational athletics.178

Two general types of exercise are recognized: isotonic (dynamic) and isometric (static).2 Isotonic exercise is associated with changes in muscle length and with rhythmic muscular contractions that develop comparatively little force. A steady state can be achieved. Isometric exercise results in sudden development of a comparatively large force with little or no change in muscle length; a steady state cannot be achieved, even temporarily. There is usually a continuum between the two types, with most physical activity incorporating isotonic and isometric components. The risk incurred by conditioning (training) may equal or exceed the risk of the competitive event itself. The heightened emotional response of an athlete before or during a sporting event may trigger a disturbance in cardiac rhythm and a loss of consciousness, putting the athlete, as well as bystanders, at risk of injury. Central to the following discussion are the type and severity of a given congenital malformation, whether or not the patient had undergone cardiac surgery, and, if so, the type and success of the operation.

CONGENITAL HEART BLOCK

CONGENITAL HEART BLOCK. Patients with congenital complete heart block occasionally perform optimally,5 but prolonged, high-intensity isotonic exercise is ill advised, and strenuous isometric exercise is unwise, even if tolerated. If a pacemaker is required, patients are allowed isotonic or isometric exercise within the limits of sensible moderation and according to the type of pacemaker used. Contact sports risk damage to the pacemaker.

ABERRANT CORONARY ARTERY BETWEEN THE AORTA AND RIGHT VENTRICULAR OUTFLOW TRACT

ABERRANT CORONARY ARTERY BETWEEN THE AORTA AND RIGHT VENTRICULAR OUTFLOW TRACT (see Fig. 8–28 Fig. 8–28 ). This uncommon anomaly can cause angina pectoris, myocardial infarction, and sudden death.179 The risk is greatest, especially in men, when the left coronary artery arises from the right aortic sinus and passes between the aorta and right ventricular outflow tract (Fig. 30–16 Fig. 30–16 ). Sudden death typically accompanies or immediately follows relatively strenuous physical effort. Expansion of the aortic root and pulmonary trunk during exercise is believed to increase preexisting acute angulation of the proximal course of the aberrant coronary artery and to reduce its lumen, especially if the lumen is slit-like.180,181 If the coronary anomaly is identified and surgically corrected, subsequent athletic activity is not restricted, provided that flow is unobstructed and myocardial ischemia is absent.

COARCTATION OF THE AORTA

COARCTATION OF THE AORTA. In this condition the proximal aorta is less distensible than is the postcoarctation aorta, accounting, in part, for the disproportionate rise in systolic blood pressure in the proximal compartment.5 The excessive rise in systolic blood pressure during isotonic exercise represents an exaggeration of the disproportionate systolic hypertension in the resting state. A disproportionate exercise-induced postoperative rise in systolic pressure is in large part related to age at the time of repair and the adequacy of repair.

CONGENITAL AORTIC STENOSIS

CONGENITAL AORTIC STENOSIS. Unoperated patients with mild congenital aortic valve stenosis (resting gradient 20 mm Hg or less) are not restricted, provided that the electrocardiogram (ECG) is normal, the response to exercise stress testing is normal, left ventricular function is normal or supernormal, and no significant disturbances in rhythm are recorded during 24-hour ambulatory electrocardiography. Patients with moderate congenital aortic stenosis (resting gradients higher than 20 but less than 50 mm Hg), especially those at the upper range, should confine athletics to low-intensity isotonic exercise. Isometric exercise, by increasing aortic root systolic pressure, reduces the gradient, but increases an already elevated left ventricular afterload. Peak systolic gradients in excess of 50 mm Hg warn against high-intensity isotonic or isometric exercise or competitive sports.

The potential risk of sudden death is a legitimate concern when advising exercise limitations in patients with aortic stenosis. Syncope that precedes sudden death is believed to be initiated by left ventricular baroreceptors activated by an exercise-induced increase in left ventricular pressure or stretch, which causes vasodilatation in skeletal muscle followed by systemic hypotension.182 Malignant ventricular arrhythmias seldom initiate syncope but are thought to be the chief cause of death after a faint. Syncope-induced hypotension is more likely to provoke disturbances in ventricular rhythm in adults with coexisting coronary artery disease than in younger patients with normal coronary arteries and no myocardial ischemia.

After valvotomy or valvuloplasty for congenital aortic stenosis, recommendations based on the above criteria do not necessarily apply, because risk is not determined by the gradient, even when it is relatively small. Athletic activity should be limited to low or moderate intensity when left ventricular internal dimensions at end diastole are increased, when aortic regurgitation is more than mild, when the scalar ECG shows residual abnormalities of repolarization at rest or with exercise, or when important disturbances in ventricular rhythm are present at rest, with exercise, or on 24-hour ambulatory ECG. These recommendations are appropriate even if left ventricular systolic function is within normal range.

PULMONARY STENOSIS

PULMONARY STENOSIS. Patients with mild pulmonary valve stenosis (peak systolic gradient <25 mm Hg) are allowed unrestricted athletic activity. When obstruction is moderate (gradient between 25 and 50 mm Hg), high-intensity competitive sports are unwise even if tolerated, because right ventricular systolic pressure can rise appreciably. When the resting peak systolic gradient exceeds 50 mm Hg—especially if there is impaired right ventricular function—isotonic exercise should be limited to mild intensity and short duration. After successful balloon dilatation or valvotomy, patients generally need few restrictions, and, as a rule, may safely participate in high-intensity competitive athletics, provided that right ventricular size, wall thickness, and function are normal. If postinterventional obstruction to right ventricular outflow is moderate or greater, athletic activity should be limited to noncompetitive low-to-moderate–intensity exercise, especially if right ventricular internal dimensions are increased and systolic function is less than normal.

ATRIAL SEPTAL DEFECT

ATRIAL SEPTAL DEFECT. The majority of young adults with uncomplicated ostium secundum atrial septal defect are asymptomatic and often have relatively normal tolerance to exercise. High-intensity competitive sports may be tolerated but are probably unwise. When surgery abolishes the shunt in childhood or young adulthood, long-term outlook is excellent, and athletic activity is unrestricted, provided that pulmonary vascular resistance is normal, sinus node function and atrioventricular conduction are normal, and the right atrial and right ventricular volumes are normal or nearly so.

VENTRICULAR SEPTAL DEFECT

VENTRICULAR SEPTAL DEFECT. A restrictive ventricular septal defect with a functionally normal heart imposes no exercise limitations. Although patients can safely participate in competitive sports without restriction, adults in this category are uncommon. An important variation on the theme is the adult who had a moderately restrictive perimembranous ventricular septal defect that decreased in size or closed spontaneously in infancy. There is consensus that such patients are physiologically normal and should be permitted unrestricted physical activity. However, two-dimensional echocardiography with Doppler interrogation and color flow imaging should be performed to determine whether the defect closed by formation of a “septal aneurysm.”5 Although there is no evidence that strenuous athletic exercise, especially isotonic, risks rupturing a septal aneurysm, it is prudent to be aware of the morphological substrate.

After surgical closure of a moderate-to-large ventricular septal defect, recommendations regarding physical activity and competitive sports depend on the postoperative pulmonary arterial pressure; the absence of significant disturbances in ventricular rhythm during maximal exercise stress testing and during 24-hour ambulatory electrocardiography; and two-dimensional echocardiographic evidence of an intact ventricular septum together with normalization of left ventricular and left atrial size and left ventricular function. It is also desirable that the 12-lead scalar ECG exhibit little or no evidence of left ventricular volume overload or right ventricular pressure overload. If these criteria are met, patients are permitted unrestricted exercise. Persistent postoperative elevation of pulmonary arterial pressure, especially if accompanied by exercise-induced right ventricular ectopic rhythms, requires limitation to isotonic physical activity of low intensity and short duration.

PATENT DUCTUS ARTERIOSUS

PATENT DUCTUS ARTERIOSUS. A small patent ductus arteriosus is of little or no physiological significance, and there are no postoperative limitations after division of an isolated restrictive patent ductus. Recommendations after division of a moderately restrictive or nonrestrictive patent ductus with large left-to-right shunt and variable elevations of pulmonary arterial pressure depend upon the guidelines just set forth for postoperative moderately restrictive to nonrestrictive ventricular septal defect.

Pulmonary vascular disease in these cyanotic patients is a contraindication to strenuous exercise. In patients with suprasystemic pulmonary vascular resistance and right-to-left shunts, even low levels of isotonic exercise tend to be accompanied by decrements in systemic arterial oxygen content and the development of tissue lactic acidosis. The exercise-induced increase in right-to-left shunt poses a special problem regarding the elimination of metabolically produced carbon dioxide, resulting in high ventilatory requirements, subjective dyspnea (Fig. 30–13 Fig. 30–13 ), and occasionally, respiratory acidosis.150,151 In nonrestrictive patent ductus arteriosus with suprasystemic pulmonary vascular resistance and reversed shunt, exercise may cause leg fatigue but comparatively little dyspnea, because the ventilatory stimuli of hypoxemia, hypercapnia, and acidemia circumvent the respiratory center. (Venous blood is delivered to the lower body but not to the vital centers of the head and neck.5)

FALLOT’S TETRALOGY

FALLOT’S TETRALOGY. In patients with this anomaly isotonic exercise provokes a fall in systemic vascular resistance and an augmentation of venous return to a right ventricle with fixed obstruction to outflow, so the right-to-left shunt increases. The subjective sensation of breathlessness is caused chiefly by the response of the respiratory center to the sudden change and blood gas composition and pH as just described. The relief of effort-induced dyspnea by squatting (see [For More Information] ), a time-honored hallmark of Fallot’s tetralogy in children, is seldom seen in adults.5 Squatting exerts its salutary effect by countering the exercise-induced fall in systemic vascular resistance and by decreasing the amount of low oxygen content inferior vena caval blood that is received by the right ventricle and shunted into the aorta during exercise. High-intensity isometric exercise in Fallot’s tetralogy abruptly reduces flow from the right ventricle into the aorta in the face of fixed obstruction to right ventricular outflow, so systemic flow suddenly falls, risking syncope and occasionally sudden death. All but low-intensity isometric exercise is proscribed.

After repair of Fallot’s tetralogy, recommendations regarding physical activity and participation in athletics depend upon patient age at operation and the presence and degree of postoperative residua and sequelae.183 After repair of Fallot’s tetralogy, patients should undergo two-dimensional echocardiography with Doppler interrogation and color flow imaging, exercise stress testing, and 24-hour ambulatory electrocardiography. If obstruction to right ventricular outflow is mild or absent, if the shunt is absent or trivial, if low-pressure pulmonary regurgitation is no more than mild to moderate, if there are no significant disturbances in ventricular rhythm, and if right ventricular size and function are normal or nearly so, limitations are not imposed upon athletic activity, either isotonic or isometric.183 Of particular concern are residual right ventricular outflow gradients that increase significantly during exercise and are accompanied by right ventricular ectopic rhythms believed to originate at the site of the ventriculotomy scar. Postoperative bifascicular block (Fig. 30–17 Fig. 30–17 ) is uncommon with current surgical techniques. Bifascicular block without the aforementioned residua or sequelae does not in itself preclude unrestricted physical activity, provided that the 24-hour ambulatory ECG records no additional evidence of impaired atrioventricular conduction.

COMPLETE TRANSPOSITION OF THE GREAT ARTERIES

COMPLETE TRANSPOSITION OF THE GREAT ARTERIES. Data regarding this anomaly are derived chiefly from patients who have undergone atrial switch operations in early life. With few exceptions, important postoperative residua and sequelae require that isotonic physical activity be restricted to mild or moderate intensity and limited duration. Recommendations regarding athletic activity after the arterial switch operation cannot currently be made. However, there is an air of cautious optimism that uncomplicated arterial switch repairs may circumvent the electrophysiological sequelae so common after atrial switch operations (Fig. 30–11 Fig. 30–11 ), while allowing the morphological left ventr

Date: 2014-12-21; view: 871