LAW No. 167 of 16 JULY 1997 OF THE REPUBLIC OF KAZAKHSTAN THE CRIMINAL CODE OF THE REPUBLIC OF KAZAKHSTAN 1 page

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.

Date: 2014-12-21; view: 1005