ACP medicine, 3rd Edition

Cardiovascular Medicine

Congenital Heart Disease

Larry T. Mahoney MD1

David J. Skorton MD2

1Professor of Pediatrics and Director of Pediatric Cardiology, University of Iowa College of Medicine

2University of Iowa College of Medicine

The authors have no commercial relationships with manufacturers of products or providers of services discussed in this subsection.

October 2003

Congenital diseases of the heart and vasculature are the most common birth defects, occurring in approximately eight per 1,000 live births. Some patients with congenital heart defects (CHDs) remain asymptomatic for many years; others survive to adulthood, thanks to the impressive progress in medical and surgical management made in recent decades. This relatively high incidence, coupled with improved management, has resulted in a large adult population of these patients: it has been estimated that almost one million adults with CHDs are currently living in the United States.1 A broad range of clinicians must now become more knowledgeable about the care of these patients,2including issues such as endocarditis prophylaxis3 [see Sidebar Selected Internet Resources for Congenital Heart Disease]. This chapter reviews CHDs most likely to be encountered in adult patients.

Selected Internet Resources for Congenital Heart Disease

International Society for Adult Congenital Cardiac Disease (ISACCD)

http://www.isaccd.org

Professional resources, patient information, and newsletter.

Canadian Adult Congenital Heart Network and the Toronto Congenital Cardiac Centre for Adults at the University of Toronto (CACHNET)

http://www.cachnet.org

Information for physicians and patients.

Grown Up Congenital Heart Patients Association (GUCH)

http://www.guch.demon.co.uk

A United Kingdom site providing information and support for patients and their families.

PediHeart

http://www.pediheart.org

Practitioner and patient information; mailing list.

Acyanotic Disorders—Shunts

ATRIAL SEPTAL DEFECTS

Atrial septal defects (ASDs) occur in three main locations [see Figure 1]: the region of the fossa ovalis (such defects are termed ostium secundum ASDs); the superior portion of the atrial septum near the junction with the superior vena cava (SVC) (sinus venosus ASDs); and the inferior portion of the atrial septum near the tricuspid valve annulus (ostium primum ASDs). The ostium primum ASDs are considered to be part of the spectrum of atrioventricular septal defects (AVSDs) [see Atrioventricular Septal Defects, below].

 

Figure 1. Anatomy of Atrial Septal Defects

Anatomy of atrial septal defects (ASDs). (OPASD—ostium primum ASD; OSASD—ostium secundum ASD; SVASD—sinus venosus ASD)

Ostium secundum ASDs are the most common variety, accounting for over half of ASDs. A frequent accompanying defect is mitral valve prolapse. Relatively less prevalent is the sinus venosus defect. Anomalous pulmonary venous return is a common associated abnormality. The proximity of the sinoatrial node to the ASD may lead to sinoatrial node dysfunction and atrial arrhythmias.

Pathophysiology

ASDs are associated with left-to-right shunts of varying degrees. The main determinants of the direction and magnitude of shunt flow are the size of the defect and the relative compliances of the left ventricle (LV) and right ventricle (RV).4

Clinical Presentation

Most patients with ostium secundum or sinus venosus ASD are asymptomatic through young adulthood. As the patient reaches middle age, compliance of the LV may decrease, increasing the magnitude of left-to-right shunting. Long-standing atrial dilatation may lead to a variety of atrial arrhythmias, including premature atrial contractions, supraventricular tachycardia, and atrial fibrillation. A substantial number of middle-aged patients will report dyspnea, particularly with exertion, even if they do not have pulmonary hypertension. Approximately 10% of patients with ostium secundum ASDs will progress to pulmonary hypertension associated with pulmonary vascular obstructive disease (Eisenmenger syndrome) [see Eisenmenger Syndrome, below]. As the pulmonary pressure rises, the left-to-right shunt will diminish and eventually be replaced by a right-to-left shunt; cyanosis and pulmonary hypertension will develop.

The hallmark of the physical examination in ASD is the wide and fixed splitting of the second heart sound. A systolic murmur (from increased pulmonary flow) is common, and if a large left-to-right shunt is present, the additional flow across the tricuspid valve may lead to a diastolic rumble reminiscent of tricuspid stenosis.

Laboratory Tests

All patients with suspected ASD should have an electrocardiogram, a chest x-ray, and an echocardiogram.

Electrocardiography

The QRS axis usually is normal in ostium secundum ASD but may be slightly rightward, and an rSR' pattern is common in the right precordial leads. In sinus venosus ASD, the axis may be normal or relatively horizontal (less than 30°). Ectopic atrial rhythms or other evidence of sinoatrial node dysfunction may be seen.

Radiologic studies

The chest x-ray reveals enlargement of the right atrium (RA), the RV, and the main pulmonary artery. The pulmonary vessels exhibit diffuse enlargement because of increased pulmonary blood flow. Magnetic resonance imaging, magnetic resonance angiography (MRA), or cardiac catheterization will identify anomalous pulmonary veins; these modalities should be considered when there is suspicion of this associated abnormality in patients with sinus venosus ASD.

The patient with secundum ASD who has pulmonary hypertension may benefit from right-sided heart catheterization to ascertain the level of pulmonary arterial pressure and resistance.

Echocardiography

Echocardiography can confirm the presence of an ASD, determine its size, permit calculation of shunt flow through it, and identify any associated anomalies.

Management

Large ASDs (defined as those with a pulmonary-to-systemic flow ratio [Qp:Qs] of over 1.5:1) should be closed to prevent the development of pulmonary hypertension and reduce the risk of paradoxical emboli. Direct surgical closure has been the method used, but devices are now available that permit catheterization-based closure of many defects.5 Postclosure management includes periodic assessment for the development of atrial arrhythmias.6 The need for endocarditis prophylaxis varies.

ATRIOVENTRICULAR SEPTAL DEFECTS

The septal leaflet of the tricuspid valve normally inserts into the septum slightly closer to the apex than does the septal leaflet of the mitral valve [see Figure 2]. Thus, the small portion of septal tissue superior to the tricuspid septal leaflet insertion separates the RA from the LV and so is called the atrioventricular septum. The term AVSD refers to a complex spectrum of disorders involving abnormalities of the atrioventricular septum and, frequently, the atrioventricular valves. Nomenclature for this spectrum of disorders has varied; synonymous terms include atrioventricular canal defect and endocardial cushion defect.

 

Figure 2. Cross-section of Atrioventricular Septum

Anatomic cross-section showing the atrioventricular septum (AVS). Note that the septal leaflet of the tricuspid valve inserts closer to the apex than does the septal leaflet of the mitral valve; thus, the AVS separates the right atrium from the left ventricle.

Pathophysiology

The spectrum of AVSDs ranges from a simple ostium primum ASD to a complete AVSD, which allows free communication among all four cardiac chambers. Variations of the anatomy of the anterior leaflet of the mitral valve and the septal leaflet of the tricuspid valve include a cleft or other abnormality in either or both of these leaflets; accessory chordae that attach in anomalous locations and alter function of the valve leaflets; or a common atrioventricular valve leaflet that bridges the septal defect. Physiologic consequences vary according to the extent of the anomaly; for example, the addition of a cleft mitral valve anterior leaflet adds varying degrees of mitral regurgitation (MR). Larger defects that also involve the ventricular septum, as well as complete AVSDs, can be associated with torrential left-to-right shunts or an admixture of venous and arterial blood.

Patients with an unrepaired complete AVSD are at risk for developing pulmonary hypertension. Eisenmenger syndrome is particularly common in AVSD patients who also have Down syndrome (trisomy 21).7

Clinical Presentation

Patients with isolated ostium primum ASDs may be asymptomatic until adulthood and then may present with fatigue, dyspnea, or symptoms related to atrial arrhythmias. Severe regurgitation of either atrioventricular valve can produce symptoms of heart failure or arrhythmias. Symptoms related to pulmonary hypertension occur in those patients who develop Eisenmenger syndrome.

Patients with only an ostium primum ASD will have clinical findings similar to those of patients with an ostium secundum ASD. The presence of a cleft in either atrioventricular valve will be associated with a pansystolic murmur. Finally, an additional pansystolic murmur can be found in patients with a complete AVSD.

Laboratory Tests

Electrocardiography

Left axis deviation is present in the majority of patients. The combination of physical findings of ASD along with left axis deviation on the ECG suggests the presence of an AVSD. RV conduction delay may be present as well.

Radiologic studies

The chest x-ray shows cardiomegaly and pulmonary vascular engorgement because of the left-to-right shunt.

Echocardiography

Echocardiography defines the specific anatomy and functional importance of the defects. Preoperative echocardiographic assessment includes estimation of the severity of atrioventricular valve regurgitation, the Qp:Qs ratio, and pulmonary arterial pressures. Postoperatively, echocardiography is used to identify and assess the significance of residual atrioventricular valve regurgitation or residual shunt.

Management

The rare patient who presents in adulthood with complete AVSD should be evaluated for pulmonary hypertension. If pulmonary pressures are normal or if pulmonary hypertension is not prohibitive (i.e., pulmonary vascular resistance is less than 50% of systemic vascular resistance), then surgical closure of the defect and repair of the atrioventricular valve anomalies should be undertaken. Postoperatively, patients are assessed for the adequacy of atrioventricular valve repair and are monitored for evidence of residual shunt. In patients with residual MR, management focuses on the need for and timing of reoperation, which may involve either repair or replacement of the mitral valve. The patient should also be followed for the development of atrial arrhythmias.

VENTRICULAR SEPTAL DEFECTS

VSDs are among the most common congenital cardiac disorders seen at birth but are less frequently seen as isolated lesions in adulthood. This is because most VSDs in infants either (1) are large and nonrestrictive (i.e., they permit equilibration of pressures between the ventricles) and therefore lead to heart failure, necessitating early surgical closure, or (2) are small and close spontaneously.

Classification systems for VSD vary but usually are referenced to the embryologic divisions of the ventricular septum into inlet, outlet, muscular, and membranous portions [see Figure 3]. The most common defects are perimembranous defects. Inlet VSDs, located more posteriorly, may be part of the spectrum of AVSDs (see above). Single or multiple defects may occur in the muscular septum (muscular VSD). Finally, outlet VSDs include subpulmonary defects, which may allow prolapse of an aortic cusp, leading to associated aortic regurgitation (AR).

 

Figure 3. Anatomic Positions of Ventricular Septal Defects

The major anatomic subdivisions of the ventricular septum are the membranous, outflow, inlet, and trabecular portions. Typical VSDs: outlet defect, perimembranous defect, marginal muscular defects, central muscular defects, inlet defect, apical muscular defects.

Pathophysiology

Nonrestrictive VSDs permit equilibration of ventricular pressures between the RV and LV, whereas small defects produce a large pressure gradient across the defect, so right heart pressures remain normal. The magnitude of shunt flow across moderate or large VSDs depends on the relative resistances of the systemic versus the pulmonary vascular bed. Rarely, clinicians may encounter adult patients who have large, nonrestrictive defects in the absence of other lesions. Moderate pulmonic stenosis at either the valve or the subvalvular level may create increased resistance to right ventricular outflow sufficient to reduce the left-to-right shunt; consequently, patients with VSD and mild to moderate pulmonic stenosis may reach adulthood without experiencing symptoms. Adults with long-standing VSD and large shunts may develop Eisenmenger syndrome.

Clinical Presentation

With the exception of those patients who contract infective endocarditis or those with Eisenmenger syndrome, adults with VSD are asymptomatic.

The classic physical finding of a restrictive VSD is a harsh, frequently palpable, pansystolic murmur heard best at the left lower sternal border. Patients who have large defects that allow equilibration of ventricular pressures may present with less impressive murmurs than patients with small defects; the reason is that with small defects, there is a large gradient between the LV and the RV, which results in severe turbulence across the defect. When aortic cusp prolapse occurs, the murmur of AR will be audible.

Laboratory Tests

Electrocardiography

The ECG may be normal or show evidence of left ventricular hypertrophy (LVH) and a pattern of so-called diastolic overload, featuring prominent Q waves in left precordial leads V5 and V6 and in leads I and aVL.

Radiologic studies

The chest x-ray may be normal or show left ventricular enlargement and pulmonary arterial engorgement. Patients who have evidence of pulmonary hypertension should undergo right heart catheterization to determine the degree of pulmonary hypertension and the level of pulmonary resistance.

Echocardiography

Echocardiography is the procedure of choice for identifying the location, size, and hemodynamic significance of a VSD; the interventricular gradient should be determined (to estimate RV pressure), and an assessment should be made of increased pulmonary blood flow.

Management

Patients with ventricular septal defects in which the Qp:Qs ratio is greater than 1.5:1 should be considered for surgical closure. Patients with pulmonary hypertension may undergo closure if pulmonary resistance is no more than about 50% of systemic resistance. Aortic cusp prolapse with resultant AR may diminish the shunt magnitude, but the presence of a prolapse constitutes an additional potential indication for closure.

Early VSD operative closures were performed through a right ventriculotomy, but now, many defects—particularly those in the perimembranous septum—are closed through a transatrial approach; such an approach leads to fewer problems with RV dysfunction and arrhythmias. Continual progress is being made in the deployment of transcatheter closure devices. Currently, however, surgical closure of VSD is still the most common approach. Postclosure management involves assessment for residual or recurrent VSD and atrial or ventricular arrhythmias, as well as assessment of RV function.

PATENT DUCTUS ARTERIOSUS

During fetal life, the ductus arteriosus connects the pulmonary artery to the aorta. Soon after birth, as a result of changes in circulating prostaglandin levels and arterial oxygen saturation, the ductus constricts; later, it closes permanently. Failure of the ductus to close leads to the condition termed patent ductus arteriosus (PDA).

Pathophysiology

The shunt from aorta to pulmonary artery increases pulmonary blood flow and return to the left heart. The size of the defect and the relative resistances of the pulmonary and systemic vascular beds determine the degree of shunting. Adults who have PDAs commonly present either with a small lesion without a large left-to-right shunt or with larger lesions and Eisenmenger syndrome.

Clinical Presentation

Except for patients with Eisenmenger syndrome, most adults with small to moderate PDAs will be asymptomatic, unless endarteritis supervenes.

The pathognomonic physical finding of PDA is the continuous murmur. A continuous murmur is one that is audible throughout systole and into diastole to any extent. The classic PDA murmur is machinelike and extends through systole and to variable degrees into diastole, peaking in intensity at the time of S2. The runoff of blood into the pulmonary artery in diastole will produce a wide pulse pressure because of low aortic diastolic pressure.

Laboratory Tests

Electrocardiography

The ECG in patients with PDA may be normal or may show evidence of LVH.

Radiologic studies

If the shunt is small, the chest x-ray may be normal. Patients with larger shunts will have associated cardiomegaly and increased vascular markings. In adults, calcium may be noted within the wall of the ductus.

Echocardiography

Echocardiography will identify the PDA and permit quantification of the Qp:Qs ratio.

Management

With the advent of reliable means of transcatheter closure of PDAs,8 common practice is to recommend that most PDAs be closed. In rare cases, the ductus may need to be closed surgically if transcatheter closure is not successful. Postoperative management includes assessment for the need of a residual shunt, although this is uncommon. Patients who develop pulmonary hypertension are managed in the same way as those with Eisenmenger syndrome [see Eisenmenger Syndrome, below].

Acyanotic Disorders—Valvular Lesions

BICUSPID AORTIC VALVE AND OTHER CAUSES OF AORTIC STENOSIS

Abnormalities of the left ventricular outflow tract are common congenital cardiac disorders. In particular, as much as 2% of the population have congenitally bicuspid aortic valves. A bicuspid aortic valve may present as an incidental finding on physical examination or echocardiography done for other reasons; as significant aortic stenosis (AS) or AR; or when it results in infective endocarditis.

Pathophysiology

A stenotic bicuspid aortic valve will produce pressure overload of the LV, which leads to LVH and eventually to heart failure, angina pectoris, or sudden death from tachyarrhythmias. Similarly, the patient with an incompetent bicuspid aortic valve will exhibit LV dilatation, initially with normal systolic function; the condition will later progress to heart failure.

Clinical Presentation

On physical examination, the cardinal sign of a bicuspid aortic valve is an early systolic ejection click. If no significant hemodynamic abnormality is present, either no murmur or a soft ejection murmur may be heard; a very mild murmur of AR is not uncommon, even with hemodynamically insignificant bicuspid aortic valves. More significant AS or AR will produce findings similar to those in patients with other disorders that cause these lesions.

Laboratory Tests

Electrocardiography

The ECG will be normal unless hemodynamically significant stenosis or regurgitation is present, in which case it will show LVH.

Radiologic studies

Chest x-ray findings in patients with hemodynamically significant bicuspid aortic valves are similar to those in patients with AS and AR from other etiologies. These may include LV dilatation in AR or in AS progressing to heart failure; the latter will also produce pulmonary congestion.

Echocardiography

Both the presence of a bicuspid aortic valve and its hemodynamic significance can be determined by echocardiography. Serial studies are useful in following the progression of the lesion.

Management

All patients with bicuspid aortic valves—even those patients with no significant stenosis or regurgitation—should be given instructions regarding endocarditis prophylaxis. Patients with AR from a bicuspid valve who are asymptomatic and have normal systolic function are followed with echocardiograms and history and physical examinations at regular intervals. If they begin to show evidence of decreasing systolic function, symptoms of heart failure, or progressive dilation of the LV, surgical replacement of the aortic valve is indicated.

Surgical or balloon valvuloplasty (in younger patients) should be considered in a patient with AS who has heart failure, syncope, or chest discomfort. A variety of surgical procedures are available, including direct repair of the valve; replacement with a bioprosthesis or mechanical prosthesis; replacement of the valve and proximal aortic root with a cadaver homograft; and the Ross procedure, in which the abnormal bicuspid valve is removed surgically and replaced with the patient's native pulmonic valve, which in turn is replaced with a cadaver homograft. The Ross procedure eliminates the need for a prosthetic valve in the aortic position. Postoperative management focuses on assessment for recurrent stenosis or progressive AR.

PULMONIC STENOSIS

Patients with pulmonic stenosis (PS) commonly have a malformed valve, with fusion of one or more of the commissures resulting in a dome-shaped valve. Most of these valves are thin and pliable. However, some patients have thickened valves, termed dysplastic.

Pathophysiology

The stenotic pulmonary valve imposes a pressure load on the ventricle, leading to right ventricular hypertrophy (RVH) and, in a subset of patients, RV failure. In patients with severely hypertrophic right ventricles, imbalance of myocardial oxygen supply and demand may lead to ischemia with attendant anginal chest discomfort and arrhythmias.

Clinical Presentation

Patients with PS of even a moderately severe degree may be asymptomatic for decades. Eventual symptoms may include chest discomfort reminiscent of angina pectoris from coronary artery disease, shortness of breath, fatigability, and symptoms of RV failure. Progression of disease and symptoms beyond adolescence is unusual.

The cardinal physical finding of PS is a systolic crescendo-decrescendo murmur of turbulence through the narrowed valve, preceded by a pulmonic ejection click. The behavior of the pulmonic ejection click during respiration may serve to differentiate it from the click of the bicuspid aortic valve. The pulmonic ejection click will exhibit a selective decrease in intensity with normal inspiration and may even disappear entirely with inspiration; in contrast, the bicuspid aortic valve click will exhibit no such selective decrease.

Laboratory Tests

All patients with suspected PS should have an ECG, a chest x-ray, and an echocardiogram.

Electrocardiography

The ECG will be normal in patients with mild to moderate PS. Severe stenosis leads to RVH.

Radiologic studies

In patients with mild to moderate degrees of PS, the chest x-ray may show no changes except mild poststenotic dilatation of the proximal pulmonary trunk.

Echocardiography

Echocardiography is extremely accurate in identifying and diagnosing the severity of PS. It can also differentiate pliable from dysplastic pulmonary valves. Finally, the echocardiogram can assess RV systolic function.

Management

Early approaches to PS consisted of closed or open surgical valvotomy. In the past 20 years, the advent of reliable methods of balloon pulmonary valvuloplasty has brought a major change in the approach to these cases.9 Particularly in patients with pliable-dome valves, the initial approach is to perform balloon valvuloplasty in cases of significant stenosis (defined by a right ventricular outflow tract gradient greater than 50 mm Hg). Some dysplastic valves are difficult to treat adequately by balloon valvuloplasty and require surgical repair or replacement. Postoperative management includes surveillance for recurrent stenosis or progressive regurgitation.

Acyanotic Disorders—Aortic Defects

COARCTATION OF THE AORTA

Coarctation of the aorta is a relatively common congenital heart defect that can be seen alone, in association with other defects (especially VSD), and in patients with Turner syndrome. A bicuspid aortic valve is a common associated lesion. Coarctation is a common cause of secondary hypertension and should be sought in all patients presenting with hypertension.

Pathophysiology

The essential pathology in coarctation of the aorta is a narrowing of the aortic lumen, usually in the vicinity of the ligamentum arteriosum, just distal to the take-off of the left subclavian artery. The narrowing of the aorta at the site of the coarctation divides the systemic circulation into a high-pressure zone proximal to the coarctation and a low-pressure zone distal to it. Hypertension may accelerate the development of atherosclerotic coronary artery disease and lead to stroke; stroke is a particular risk when aneurysms of the circle of Willis are present, as occurs with increased incidence in patients with coarctation.

Clinical Presentation

Although lower-extremity claudication may occur, even patients with significant coarctation of the aorta may be entirely asymptomatic. The cardinal feature on physical examination is the difference in pulses and blood pressures above versus below the coarctation. Palpation of the radial and femoral arteries in a normal patient will reveal simultaneous arrival or, perhaps, slightly earlier arrival of the pulse at the femoral artery. In coarctation of the aorta, the femoral pulse will occur later than the radial and is often lower in amplitude. Blood pressure should be evaluated in both arms and either leg when seeking coarctation of the aorta, because of variations in anatomy. When the coarctation is distal to the origin of the left subclavian artery, both arms will be in the high-pressure zone and both legs in the low-pressure zone. However, some coarctations are proximal to the left subclavian. Thus, the left arm and both legs will be in the low-pressure zone, and the diagnosis may be missed if only the left arm is used for measuring blood pressure. More rarely, there may be an anomalous origin of the right subclavian artery; the artery may arise directly from the aorta distal to the left subclavian instead of from the brachiocephalic (innominate) artery. In addition to differential blood pressures, physical examination may also reveal a murmur across the coarctation that can be best heard in the left infrascapular area.

Laboratory Tests

Electrocardiography

The ECG in patients with coarctation will show varying degrees of LVH, depending on the severity of the narrowing.

Radiologic studies

Dilatation of the aorta proximal and distal to the coarctation site may lead to a so-called 3 sign on chest x-ray. Rib notching is often present; this term refers to apparent effacement, or so-called scalloping, of the lower edges of ribs (usually the third through ninth ribs) because of large, high-flow intercostal collateral vessels that develop as a compensatory mechanism to bypass the narrowing at the coarctation site. Absence of rib notching does not rule out coarctation of the aorta, however.

MRI with MRA can be used effectively to identify coarctation and the collateral circulation. It is also useful for postrepair detection of aneurysms or restenosis at the site of repair.

Echocardiography

Echocardiography is extremely helpful in identifying the site of the coarctation by direct visualization, as well as in measuring the pressure gradient across the coarctation site. Echocardiography can also identify bicuspid aortic valves, which frequently accompany coarctation of the aorta.

Management

Coarctation that is sufficient to produce hypertension should always be treated, either surgically or by balloon angioplasty with stent placement. The longest experience is with surgical excision of the coarctation and either end-to-end anastomosis or graft interposition. In recent years, balloon angioplasty has increasingly proved to be a viable alternative for both initial treatment of coarctation and for treatment of restenosis at the coarctation site that develops after repair or angioplasty.10

Both before and after correction of coarctation, patients are at risk for infective endarteritis in the vicinity of the coarctation or distal to it and should be treated with prophylactic antibiotics before procedures of risk.

Cyanotic Disorders

DEFINITION AND MECHANISMS

Central cyanosis is caused by an intracardiac shunt or an intrapulmonary right-to-left shunt. Cyanosis becomes evident when reduced (unoxygenated) capillary hemoglobin reaches about 5 g/dl, although this depends on the total hemoglobin concentration: cyanosis is more readily apparent in a patient with polycythemia and is less apparent in a patient with anemia. Mild cyanosis is difficult to detect. Generally, cyanosis does not become clinically apparent until the oxygen saturation falls below 85% (assuming a normal hemoglobin level). Patients with long-standing arterial desaturation will develop clubbing of the fingernails and toenails. Clubbing is characterized by thickening and widening of the nailbeds and loss of the angle between the nail and nail bed, producing a convex nail.

It is helpful to categorize cyanotic CHDs in terms of their effect on pulmonary blood flow. Defects producing decreased pulmonary blood flow include tetralogy of Fallot, tricuspid atresia, Ebstein anomaly, and pulmonary atresia. Defects associated with increased pulmonary blood flow include persistent truncus arteriosus, transposition of the great arteries with or without VSD or PDA, total anomalous venous return, a single or common ventricle, and hypoplastic left heart syndrome. Acyanotic patients with large left-to-right shunts may develop pulmonary vascular occlusive disease (Eisenmenger syndrome).

Adult patients with cyanotic CHD are at increased risk for hyperviscosity secondary to erythrocytosis. The erythrocytosis develops as a compensatory mechanism for red cell oxygen desaturation: a significantly increased red cell mass is necessary to deliver an adequate volume of oxygen to peripheral tissues, given the sometimes severe degree of desaturation. Venous and arterial thrombosis with secondary cerebrovascular accidents have been well documented in cyanotic CHD and have been attributed both to the increased red blood cell mass and to associated iron deficiency anemia, which also increases blood viscosity. This risk is increased in the presence of hypertension or atrial fibrillation and in patients with a history of phlebotomy and microcytosis, suggesting the need for a more conservative approach to phlebotomy and aggressive treatment of iron deficiency.

EISENMENGER SYNDROME

A serious complication of long-standing left-to-right shunts in the atria, ventricles, or great arteries is the development of severe, irreversible pulmonary hypertension, which is termed Eisenmenger syndrome.

Pathophysiology

Normally, the pulmonary vascular resistance is substantially lower than systemic vascular resistance; thus, large intracardiac or great artery communications tend to produce left-to-right shunting. As pulmonary vascular resistance rises, resistance to flow into the pulmonary circulation will eventually exceed that into the systemic circulation, and right-to-left shunting will occur. This will result in varying degrees of cyanosis as well as other physical findings of pulmonary hypertension. Unlike patients with polycythemia vera or polycythemia from chronic obstructive pulmonary disease, patients with Eisenmenger syndrome will often require hematocrits in the 60s, or even low 70s, to deliver sufficient oxygen to tissues to avoid ischemic symptoms.

Clinical Presentation

Patients with Eisenmenger syndrome may be asymptomatic except for cyanosis. Eventually, many patients will note decreased exercise tolerance and chest discomfort, often reminiscent of angina pectoris. If secondary erythrocytosis reaches severe levels, patients may develop symptoms of hyperviscosity, including visual disturbances, headaches, and other complaints.

Physical examination of a patient with Eisenmenger syndrome will reveal manifestations of pulmonary hypertension, including a loud pulmonary component of the second heart sound and the high-pitched diastolic murmur of high-pressure pulmonary regurgitation (the Graham Steell murmur). Additional findings include cyanosis, clubbing, and RV lift or heave.

Laboratory Tests

Electrocardiography

The ECG shows right axis deviation and RVH, exhibited as tall R waves and ST-T abnormalities in V1 through V3.

Radiologic studies

The chest x-ray will show enlarged central pulmonary arteries with peripheral arterial pruning. Cardiomegaly with specific chamber enlargement will reflect the underlying defect. Right-sided cardiac catheterization often is needed to assess pulmonary arterial pressure and resistance.

Echocardiography

Echocardiography can identify and quantify the underlying cardiac shunt and provide an estimate of right heart pressures.

Management

Patients with Eisenmenger syndrome may live for decades after the diagnosis is made.11 Alternatively, sudden death from ventricular arrhythmias may occur. Because pulmonary resistance is high and fixed in these patients, care needs to be taken to avoid situations that may lead to sudden decreases in systemic vascular resistance, which would exacerbate the right-to-left shunting, sometimes in a life-threatening manner. This would include avoidance of overly hot environments and dehydration; in addition, care should be taken during anesthesia or when using vasodilator drugs. Pregnancy is another state in which systemic vascular resistance falls; thus, pregnancy is extremely dangerous for a mother with pulmonary hypertension, as well as for her fetus. Iron deficiency should be treated if present. Only rarely will phlebotomy be required to relieve symptoms of hyperviscosity. A relatively recent therapeutic option for Eisenmenger syndrome is the use of prostacyclin12 or endothelin-related drugs13 to lower pulmonary vascular resistance. Heart-lung or lung transplantation has been successfully performed in some patients with Eisenmenger syndrome.14

TETRALOGY OF FALLOT

Pathophysiology

Tetralogy of Fallot is the most common form of cyanotic congenital heart disease. Classically, the syndrome includes pulmonary stenosis (subvalvar, valvar, supravalvar, or a combination of all of these), RVH, subaortic VSD, and dextropositioning of the aorta so that it overrides the interventricular septum. Associated anomalies include right aortic arch (25%), atrial septal defect (10%), and coronary artery anomalies (10%).15 Approximately 15% of patients with tetralogy of Fallot have a deletion of chromosome 22q11 (CATCH 22 syndrome: cardiac anomalies, abnormal facies, thymic hypoplasia, cleft palate, hypocalcemia, and 22q11 deletion).16

Surgical Repair in Childhood

Current surgical practice warrants early repair, usually in the first year of life. Without surgery, survival beyond 20 years of age is uncommon.

Surgical repair consists of patch closure of the VSD and alleviation of the RV outflow tract obstruction by one or more of the following methods: infundibular muscle resection, pulmonary valvotomy, outflow tract or transannular patch augmentation, and patch augmentation of the main or proximal branch pulmonary arteries. In some cases, it is necessary to place a conduit from the RV to the pulmonary artery. The conduit may be valved or nonvalved, and it may be bioprosthetic or a homograft.

When pulmonary blood flow is inadequate, surgical repair includes a shunt from the systemic circulation to the pulmonary artery to provide additional pulmonary flow. This may consist of a Blalock-Taussig shunt, a Potts shunt, or a Waterston shunt. The classic Blalock-Taussig shunt connects the subclavian artery to the pulmonary artery; the modified form comprises an interposed tube graft, usually of expanded polytetrafluoroethylene [Gore-Tex]. A Potts shunt connects the descending aorta to the left pulmonary artery. A Waterston shunt connects the ascending aorta to the right pulmonary artery [see Figure 4].

 

Figure 4. Systemic Artery-to-Pulmonary Artery Shunts

Systemic artery-to-pulmonary artery shunts. The Blalock-Taussig shunt connects the subclavian artery to a pulmonary artery; the Waterston shunt connects the ascending aorta to the right pulmonary artery; and the Potts shunt connects the descending aorta to the left pulmonary artery.

Clinical Presentation after Repair

In patients who have undergone surgical repair of tetralogy of Fallot, the examination focuses on residual defects. Not uncommonly, these patients have murmurs related to residual outflow tract obstruction and mild to severe pulmonary regurgitation (PR), which produces a to-and-fro murmur. The severity of RV outflow tract obstruction directly determines the presence and degree of cyanosis. Systolic ejection murmurs are inversely related to the severity of the obstruction: a short, soft murmur suggests severe obstruction with a large right-to-left ventricular level shunt and minimal forward flow in the pulmonary artery, whereas a long, harsh murmur suggests minimal obstruction.

Patent shunts will produce a continuous murmur. The degree of cyanosis will depend on the adequacy of pulmonary blood flow provided by the shunt.

A residual VSD may be detected. With increasing RV volume overload, the patient may experience exercise intolerance, right heart failure, and arrhythmias.

Laboratory Data

Electrocardiography

In patients who have undergone operative repair of tetralogy of Fallot, the ECG typically shows sinus rhythm, right axis deviation, and RVH; most of these patients also have right bundle branch block. Atrial and ventricular arrhythmias may be detected, especially on a 24-hour monitoring study.

Radiologic studies

The findings on chest x-ray vary with the surgical history. A right aortic arch may be noted. The pulmonary artery segment is concave because of the variable degree of pulmonary artery hypoplasia, and the RVH results in an upturned apex; together, these produce the classic finding of a boot-shaped heart. Surgical intervention may result in significant pulmonary regurgitation that eventually will lead to volume overload of the heart, producing cardiomegaly. Over time, patch augmentation of the outflow tract may become aneurysmal, which may be indicated by an enlarged pulmonary artery segment. Asymmetrical pulmonary blood flow suggests significant branch pulmonary artery obstruction and can be best quantitated by a pulmonary flow study. MRI with MRA is very useful to identify residual defects and assess ventricular function, especially in patients with poor acoustic windows and inadequate echocardiographic studies.

Echocardiography

Echocardiography will establish the presence and severity of any residual defects, including progressive enlargement of the RV secondary to pulmonic regurgitation, a residual VSD, and continuous flow in a palliative shunt. Doppler studies will demonstrate the magnitude of the residual outflow tract gradient. The ascending aorta often is enlarged.

Management

Patients who have undergone repair of tetralogy of Fallot must be regularly monitored for progression of residual defects, particularly those with pulmonary regurgitation and conduit obstruction. Branch pulmonary artery stenosis may be approached with balloon angioplasty and stent placement. Repeat surgery should be considered in patients with a significant residual VSD; in patients whose RV pressure is greater than two thirds the systemic pressure because of residual obstruction; in patients with RV enlargement secondary to severe pulmonary regurgitation (which may mandate placement of a bioprosthetic valve, especially if there is associated tricuspid regurgitation [TR]); and in those with reduced exercise tolerance.17 Reoperation in adults can be performed with low risk. Aortic valve or aortic root replacement is occasionally required because of progressive root dilatation and AR.18 Ventricular arrhythmias, which are detected in 40% to 50% of patients, have been associated with older age at primary repair, RV volume overload, and QRS prolongation. Marked widening of the QRS to more than 180 msec and LV dysfunction have been identified as risk factors for sudden cardiac death. In such cases, consideration should be given to prophylactic placement of an implantable cardiac defibrillator.19 Patients should be counseled to follow endocarditis prophylaxis during procedures that place them at risk.

DEXTROTRANSPOSITION OF THE GREAT ARTERIES

Pathophysiology

In the most common form of transposition of the great arteries (TGA), dextro-TGA (D-TGA), the aorta arises in an anterior position from the RV, and the pulmonary artery arises posteriorly from the LV. There is complete separation of the pulmonary and systemic circulations: systemic blood flow traverses the right heart and enters the aorta, whereas pulmonary blood flow traverses the left heart and enters the pulmonary artery. Most surviving patients have a patent ductus arteriosus and foramen ovale, permitting mixing of the two circulations. About one third have associated anomalies, including ASD and VSD. Left ventricular outflow tract obstruction is not uncommon. Unless intracardiac mixing is improved, survival beyond the first year is unusual.

Surgical Repair in Childhood

Initial treatment of D-TGA includes infusion of prostaglandin E to maintain patency of the ductus arteriosus and balloon septostomy (Rashkind procedure) to permit better mixing at the atrial level. Surgery initially consisted of redirecting the systemic venous return to the LV and the pulmonary venous return to the RV. These so-called atrial switch operations (Mustard or Senning procedures), which used a baffle within the atria, restored physiologic circulation but required the RV to function as the systemic ventricle. The arterial switch operation has replaced the atrial switch operation, at least in patients who have normal function of both semilunar valves. In the arterial switch operation, the pulmonary artery and aorta are first transected above the semilunar valves and coronary arteries, and then they are switched. The aorta is connected to the neoaortic valve (formerly the pulmonic valve) arising from the LV, and the pulmonary artery is connected to the neopulmonary valve (formerly the aortic valve) arising from the RV. The coronary arteries are relocated to the neoaorta.

Patients with D-TGA and a large VSD may undergo the Rastelli procedure. The pulmonary artery is divided and oversewn. Flow from the LV must pass through the septal defect and is directed by a baffle to the aortic valve. A conduit from the RV to the pulmonary artery allows egress from the ventricle to the pulmonary circulation.

Clinical Presentation after Repair

Physical findings relate to the presence of associated anomalies (i.e., murmurs of VSD, PS, or PDA). Similarly, the larger the septal defect, the less severe the cyanosis.

Laboratory Tests

Electrocardiography

The ECG in patients with the atrial switch shows right axis deviation and RVH. In patients with the arterial switch, the ECG may be normal, provided coronary blood flow is not compromised.

Radiologic studies

Patients who have had the atrial switch procedure generally have cardiomegaly from a dilated RV, and the pulmonary artery may show preferential flow to the right lung. Patients with the arterial switch repair are likely to have normal heart size.

Echocardiography

Echocardiography is used to assess associated residual defects: depressed RV function, progressive TR, left ventricular outflow tract obstruction, residual VSD, or coronary artery perfusion abnormalities.

Management

The long-term outlook after the atrial switch is quite good, with actuarial survival of 80% at 28 years and 76% of survivors having no symptoms.20 However, these patients must be monitored for progressive RV enlargement and TR leading to ventricular dysfunction. Although this complication occurs in only 3% of cases, such patients may require cardiac transplantation if medical therapy is ineffective. Atrial arrhythmias, including sick sinus syndrome, are common. The atrial baffle may cause either systemic or pulmonary venous obstruction, which is addressed either by reoperation or by balloon angioplasty and stent placement.

The long-term prognosis of patients with the arterial switch is less well known, but arrhythmias are thought to be less frequent and to occur secondary to imperfections in the operative procedure.21 Patients should undergo nuclear medicine studies or stress testing to monitor for inadequate coronary perfusion secondary to coronary artery reimplantation abnormalities. Stenosis of the pulmonary artery (the most common complication) or stenosis at aortic anastomosis sites may occur. Complications of the Rastelli procedure include subaortic obstruction (baffle or VSD obstruction), conduit stenosis (with or without regurgitation), baffle leak, and branch pulmonary artery stenosis. Significant residual defects require reoperation.17

THE UNIVENTRICULAR HEART

Pathophysiology

A functional single ventricle may result from hypoplastic left heart syndrome (aortic atresia, mitral atresia, or both), tricuspid atresia, pulmonary atresia with intact ventricular septum, or an unbalanced AVSD resulting in hypoplasia of either the RV or LV.

Surgical Repair in Childhood

The initial presentation of univentricular heart in childhood may include severe cyanosis associated with a marked decrease in pulmonary blood flow, mild cyanosis and heart failure associated with intracardiac admixture of circulations and excessive pulmonary blood flow, or nearly balanced systemic and pulmonary blood flows and mild cyanosis. Patients who survive to adulthood generally have undergone one or more palliative surgical procedures; these include the Norwood, Glenn, and Fontan procedures.

Norwood

The Norwood operation establishes a single outlet from the single ventricle by anastomosing the hypoplastic ascending aorta to the main pulmonary artery, producing a so-called neoaorta and connecting the distal pulmonary artery to a systemic shunt, usually a modified Blalock-Taussig shunt [see Figure 5, part a]. Often, an atrial septectomy is required to allow complete mixing at the atrial level.

 

Figure 5. Repair of Functional Single Ventricles

Stages in the repair of functional single ventricles (see text for details). (a) Norwood; (b) bidirectional Glenn; (c) lateral tunnel; (d) extracardiac conduit.

Glenn

The bidirectional Glenn procedure involves anastomosis of the SVC to the pulmonary artery. It includes takedown of a previously placed shunt and repair of any branch pulmonary artery stenosis [see Figure 5, part b]. The term bidirectional refers to the fact that the right pulmonary artery remains in continuity with the left pulmonary artery; this contrasts with the classic Glenn procedure, which involves anastomosis of the SVC to a right pulmonary artery that has been disconnected from the main and left pulmonary arteries. The bidirectional Glenn procedure is now done at 4 to 6 months of age.

Fontan

The Fontan procedure is the final palliative procedure, providing direct connection of flow from the SVC and inferior vena cava (IVC) to the pulmonary circuit. Initially, this was a one-stage procedure that involved attaching the RA to the pulmonary artery or RV outflow tract and was performed in patients older than 4 years. Current practice is to stage the anastomosis of SVC and IVC to the pulmonary circuit, with the final stage, total cavopulmonary artery anastomosis, occurring at 2 to 3 years of age. The IVC is connected to the pulmonary artery either by a lateral tunnel placed in the RA to direct blood from the IVC to the proximal SVC stump, which is then attached to the pulmonary artery [see Figure 5, part c], or by an extracardiac conduit connecting the IVC to the pulmonary artery directly [see Figure 5, part d]. With any of these routes of flow, a small communication (fenestration) may be made between the caval blood flow conduit and the functional left atrium. Pulmonary blood flow is achieved by passive venous return without assistance of a ventricular pumping chamber. Any mild alteration of pulmonary pressure or resistance will impair adequacy of pulmonary blood flow.

Clinical Presentation after Repair

Clinical features are variable. Some patients may be well palliated, with near-normal oxygen saturation, acceptable activity levels, and negligible findings on cardiac examination. Others will demonstrate progressive heart failure as the single ventricle (especially if it is an anatomic RV) succumbs to the increased pressure and volume overload secondary to progressive atrioventricular valve regurgitation and myocardial dysfunction. Both atrial and ventricular arrhythmias are common. The sluggish pulmonary blood flow may predispose to in situ thrombosis and pulmonary embolism, which in turn will impede pulmonary blood flow by raising pulmonary arterial pressure.

Laboratory Tests

Electrocardiography

ECG findings are quite variable and may include atrial or ventricular enlargement, axis deviation, conduction abnormalities, and arrhythmias.

Radiologic studies

The chest x-ray may show progressive cardiomegaly. Pulmonary vascular markings may be unequal, indicating stenosis of one or more pulmonary artery branches. MRI with MRA may show areas of branch pulmonary artery stenosis and progressive changes in chamber size and ventricular function.

Echocardiography

Echocardiographic studies are aimed at following the progression of atrioventricular valve regurgitation, ventricular enlargement, and dysfunction, as well as detecting so-called smoke or clots in the systemic venous-to-pulmonary artery circuit.

Management

After surgical correction, patients demonstrate significant limitations in exercise tolerance because they rely on passive pulmonary blood flow that does not increase maximally with exertion. Postoperative arrhythmias are common. Arrhythmias may need to be managed medically, because radiofrequency ablation techniques may be limited by access problems secondary to the extracardiac or lateral tunnel connections between the venous circulation and the pulmonary artery. The need for reoperation after the Fontan procedure is infrequent, with the most common indication being placement of a mechanical pacemaker. Protein-losing enteropathy (PLE) is a serious problem after the Fontan operation. Its cause is not known but probably relates to increased systemic venous and thoracic duct pressures. There may also be a local autoimmune or allergic component in the intestinal wall. PLE is characterized by peripheral edema, malabsorption, and a low serum protein level. Complications have become less frequent with staged surgery and provision of an atrial fenestration. Some older patients may benefit from conversion of classic Fontan to a total cavopulmonary artery anastomosis. Cardiac transplantation may be necessary for systemic ventricular failure or intractable PLE.17

EBSTEIN ANOMALY OF THE TRICUSPID VALVE

Pathophysiology

This uncommon anomaly of the tricuspid valve consists of adherence of the posterior and septal leaflets to the myocardium—causing a downward displacement of the functional annulus toward the RV apex—and enlargement of the anterior leaflet. The end result is an atrialization of the RV with resultant TR. In patients who present early in life, Ebstein anomaly is often found in association with other defects, including ASD and PS. Accessory pathways and clinical evidence of preexcitation are not uncommon, and arrhythmias are the most common presenting features in adults. There is an association with maternal lithium administration.

Clinical Presentation

Ebstein anomaly can become clinically evident at any age; the natural history of this lesion ranges from death in early life to adult survival without surgery, depending on the degree of regurgitation and whether significant arrhythmias are present. Cyanosis may occur, in neonates or adults, secondary to right-to-left shunting at the atrial level. Adult patients may complain of fatigue, shortness of breath, palpitations, or syncope. On auscultation, a murmur of TR is apparent and is often associated with a gallop rhythm, multiple systolic ejection sounds, and a widely split second sound.

Laboratory Tests

Electrocardiography

ECG findings are quite variable. The PR interval may be normal; short, with preexcitation; or prolonged. The axis may be superior or rightward, with or without a right bundle branch block. There may be evidence of RA enlargement. Arrhythmias are detected in 43% of adolescents and adults.22

Radiologic studies

The chest x-ray may show cardiomegaly with RA enlargement. Cardiac catheterization is not necessary unless there is concern regarding coronary artery disease or need for electrophysiologic assessment and possible radiofrequency ablation.

Echocardiography

Echocardiography can confirm the diagnosis and the degree of the tricuspid valve displacement (which may vary from mild tethering of the septal leaflet to severe apical displacement) and characterize the severity of TR [see Figure 6]. The anterior leaflet is large and sail-like and may produce RV outflow obstruction. The atrial septum should be assessed for size of defect and magnitude of shunting.

 

Figure 6. EKG in Ebstein Abnormality

Echocardiograms of a patient with Ebstein anomaly. (a) Apical four-chamber view. The arrow indicates apical displacement of tricuspid leaflet. (b) Color Doppler flow image demonstrating severe tricuspid regurgitation (TR), originating deep in the right ventricle from the displaced tricuspid valve leaflet. (ARV—atrialized right ventricle; LA—left atrium; LV—left ventricle; RA—right atrium; RV—right ventricle)

Management

Surgery is recommended for patients with symptomatic heart failure and cardiomegaly, cyanosis, or arrhythmias; tricuspid valvuloplasty is preferred over valve replacement.15 Surgery is not recommended for asymptomatic patients,22 although some authors have advocated surgery if significant cardiomegaly is present, because this may be a better predictor of sudden death than functional status.23

Acknowledgment

Figure 1 through 5 Alice Y. Chen.

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Editors: Dale, David C.; Federman, Daniel D.