Adult congenital heart disease and the surgical patient


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Adult congenital heart disease and the surgical patient

  1. 1. DK091X_C013.qxd 7/2/07 4:56 PM Page 269 13 Adult Congenital Heart Disease and the Surgical Patient Matthew Barnard The Heart Hospital, London, U.K. Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 INTRODUCTION In the future, there will be more adults than children with congenital heart disease— this already applies to Tetralogy of Fallot which is the commonest of the cyanotic lesions. Fewer than 20% of patients with congenital heart disease would survive to adult life without treatment. As a result of modern medical and surgical techniques, nearly all deaths now occur in adults and not children. As a result, there is an increas- ing population of patients with adult congenital heart disease who require long-term follow-up and who may require medical and surgical interventions during the course of their lives. The management of adults with congenital heart disease poses clinical, organ- izational, and logistical challenges including fundamental questions relating to the For personal use only. appropriate institutional environment, facilities, staff, training, and educational pro- grams. There remains a lack of consensus as to whether this type of service should be organized at the local, regional, or supraregional level. Although many accept that complex cases benefit from concentration in specialized centers, there remains uncertainty over care boundaries for the larger number of patients with less com- plicated lesions (1). The complex medical and psychosocial problems of these patients requires support from a variety of specialists, and physicians who care for them must be trained in dealing with adults and acquired disorders, while maintaining invalu- able input from pediatric cardiologists and surgeons (2). Completely normal cardiovascular anatomy and physiology is rarely achieved by corrective surgery during childhood (3). One important principle is that patients have had their cardiac lesions repaired—not cured (4). Many patients will continue to manifest residua of their underlying pathology and or sequelae of therapeutic interventions. CLASSIFICATION OF CONGENITAL HEART DISEASE Congenital heart disease embraces a considerable number of complex conditions. A number of commonly used terms are brought together in Table 1. There are sev- eral ways of classifying adult congenital heart disease. The number of different lesions and heterogeneity within each lesion dictate that a reductionist approach is useful. One distinction is between cyanotic and noncyanotic patients. Cyanotic patients often have more comorbid medical problems and experience greater num- bers of serious perioperative complications than noncyanotics (5). Lesions are often broadly categorized into simple, intermediate, and complex (Table 2). Although sim- plistic, this facilitates decisions about management, monitoring, and referral to spe- cialist centers. Patients with simple lesions can be managed in most settings with minimal alterations to routine care other than antibiotic prophylaxis and anticoagu- lation. Complex patients should be referred to specialist units if sufficiently stable to 269
  2. 2. DK091X_C013.qxd 7/2/07 4:56 PM Page 270 270 Barnard TABLE 1 Some Commonly Used Terms in Congenital Heart Disease ASD Atrial septal defect; commonly classified into ostium primum (partial AVSD), ostium secundum, sinus venosus Ostium primum are defects in the inferior septum and comprise the atrial component of AVSD; secundum defects are absences in the oval fossa region; sinus venosus defects occur around the superior atriocaval junction and are associated with pulmonary veins draining anomalously to the superior vena cava AVSD Atrioventricular septal defect, often called AV canal defect or Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 endocardial cushion defect; defect including primum septal defect and separate atrioventricular orifices (partial) or primum septal defect and ventricular septal defect and common atrioventricular orifice (complete) or intermediate forms Balanced circulation Relatively equal systemic and pulmonary blood flow Blalock Taussig shunt Connection of subclavian artery to ipsilateral pulmonary artery; classical shunt involved transection of subclavian artery and end-to-side anastomosis to pulmonary artery; modified Blalock Taussig shunt uses synthetic interposition graft; used to increase pulmonary blood flow, albeit using inefficient recirculation of systemic blood Concordance Connection of two structures the same side morphologically—left atria to left ventricle or right ventricle to pulmonary artery For personal use only. Discordance Connection of morphologically left structure to morphologically right structure, e.g., left ventricle to pulmonary artery Double inlet ventricle Both atrioventricular valves (or greater than 50% of each) connect to one ventricle; usually left ventricle Double outlet ventricle Both great vessels (or greater than 50% of each) arise from one ventricle; usually right ventricle Fenestration Surgically created hole in atrial or ventricular septum or intracardiac baffle; diverts proportion of blood from right to left heart in situations where normal passage through the lungs is prevented by elevated pulmonary resistance; cardiac output thereby maintained or increased—at the expense of cyanosis Fontan Surgeon who described the Fontan procedure; now usually refers to circulatory arrangement whereby systemic veins are connected to the pulmonary arteries—without a right ventricle; the connection may be intracardiac or extracardiac Glenn Cavopulmonary shunt; connection of the superior vena cava to the pulmonary artery; bidirectional Glenn refers to connection to joined right and left pulmonary arteries Hemitruncus Right or left pulmonary artery from aorta Konno Enlargement of aortic annulus and left ventricular outflow tract Left SVC Persistence of connection between left subclavian vein and left internal jugular vein with coronary sinus; coronary sinus usually dilated, and if unroofed or fenestrated associated with intracardiac left to right shunt Malposition Malposition of the atrial or ventricular septum that results in valve overriding the septum (Continued)
  3. 3. DK091X_C013.qxd 7/2/07 4:56 PM Page 271 Adult Congenital Heart Disease and the Surgical Patient 271 TABLE 1 Some Commonly Used Terms in Congenital Heart Disease (Continued) Mustard Intraatrial switch procedure for TGA; intraatrial baffles direct pulmonary venous blood to the right ventricle and systemic venous blood to the left ventricle; results in physiological appropriate but anatomically incorrect circulation Overriding Valve which is positioned over the ventricular septum Rastelli VSD closure incorporating baffling mitral inflow to (malpositioned) aorta; external conduit or homograft to connect right ventricle to pulmonary artery Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 Ross pulmonary autograft Replacement of the aortic valve with native pulmonary valve; replacement of the pulmonary valve with cadaveric homograft Senning Similar to Mustard procedure; intra-atrial baffling to redirect venous blood to the opposite ventricle in TGA Single outlet Single vessel arising from the heart Single ventricle One functional ventricle, although there is usually a second vestigial ventricle Straddling Valve with attachments on both sides of the ventricular septum; limits anatomical repair Transposition great arteries Ventriculoarterial discordance; aorta from right ventricle, pulmonary artery from left ventricle For personal use only. Truncus arteriosus Single arterial vessel arises from the heart; systemic and pulmonary arteries branch from the single vessel Univentricular connection Both atria connected to one ventricle; connection is either via two valves in the absence of one of the atrioventricular valves and an ASD Abbreviations: ASD, atrial septal defect; AVSD, atrioventricular septal defect; SVC, superior vena cava; TGA, trans- position of the great arteries; VSD, ventricular septal defect. be transferred. At least some patients with intermediate lesions will be managed in nonspecialist centers and so will pose the biggest challenge to general anesthetists and intensivists. Some specific and general conditions which suggest transfer to a specialist unit would be appropriate are listed in Table 3. PATHOPHYSIOLOGY OF CONGENITAL HEART DISEASE Congenital cardiac lesions run the gamut from simple septal defects to extremely complex anatomical rearrangements. All may be considered in terms of the primary effects of the cardiac lesion and the secondary effects seen as the condition evolves. Primary and secondary pathophysiological features of patients with congenital heart disease (CHD) are outlined in Table 4 and the effects of specific lesions are dis- cussed in more detail later in this chapter. There are a number of important general considerations however. Cyanosis and Hyperviscosity Hypoxemia is caused by either right to left shunting or mixing of pulmonary and sys- temic venous blood in a common chamber. The main adaptive response to hypox- emia is secondary erythrocytosis. Blood viscosity increases almost exponentially with
  4. 4. DK091X_C013.qxd 7/2/07 4:56 PM Page 272 272 Barnard TABLE 2 Classification of Congenital Heart Lesions Complex (best managed in Moderate (can often be managed Simple (can be managed in specialist unit) in general hospitals; consider most settings using referral if noncardiac surgery normal management is major, or recent cardiology principles) review demonstrates complications) Conduits Aorta-LV fistulae Isolated aortic valve disease Cyanotic Anomalous pulmonary veins Isolated mitral valve Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 disease Double outlet ventricle AV canal defects Isolated ASD Eisenmenger Coarctation Small VSD Fontan Ebsteins anomaly Mild pulmonary stenosis Mitral atresia Infundibular RVOTO Repaired PDA Single ventricle Primum ASD Repaired ASD Pulmonary atresia Unclosed PDA Repaired VSD Pulmonary vascular disease Pulmonary regurgitation (moderate/severe) Transposition great arteries Pulmonary stenosis (moderate/severe) Tricuspid atresia Sinus Valsalva fistula/aneurysm Truncus arteriosus Sinus venosus ASD Other AV or VA Sub/supravalvar aortic For personal use only. connection abnormalities stenosis Tetralogy of Fallot VSD with other lesion Abbreviations: LV, left ventricular; AV, atrioventricular; VA, ventricular arterial; ASD, atrial septal defect; PDA, patent ductus arteriosus; RVOTO, right ventricular outflow tract obstruction. hematocrit. In the presence of iron deficiency, microcytosis results in erythrocyte rigid- ity. Increased viscosity should be borne in mind when considering optimal hematocrits for these patients. Venesection is used for the relief of symptoms but preoperative venesection is no longer practiced in the absence of symptomatic hyperviscosity (a constellation of hematological and neurological symptoms, including headaches, visual disturbances, and embolic complications) (1). Hemoglobin concentrations may be greater than 19 preoperatively, and a postoperative drop to approximately 14 would be acceptable. Coagulopathies and gallstones are other consequences of polycythemia. TABLE 3 Abnormalities Best Treated in Specialist Congenital Heart Unit Valvular atresia Eisenmenger reaction Double inlet/outlet ventricle Pulmonary hypertension Malposition of great arteries Chronic hypoxemia Fontan circulation QP:QS > 2:1 Single/common ventricles Ventricular outflow gradient >50 mmHg Transposition of great arteries ↑PVR Atrial switch procedure Secondary polycythemia Rastelli procedure Abbreviations: QP, pulmonary blood flow; QS, systemic blood flow; PVR, pulmonary vascular resistance.
  5. 5. DK091X_C013.qxd 7/2/07 4:56 PM Page 273 Adult Congenital Heart Disease and the Surgical Patient 273 TABLE 4 Features of Congenital Heart Disease Primary Secondary Shunts Arrhythmias Stenotic lesions Cyanosis Regurgitant lesions Infective endocarditis Myocardial ischemia Paradoxical emboli Polycythemia Pulmonary hypertension Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 Ventricular dysfunction Cyanosis in patients with congenital heart disease may be accompanied by con- genital syndromes, airway and thoracic cage abnormalities, tracheobronchial com- pression, and kyphoscoliosis. Brain abscesses, impaired cognitive function, and chronic neurologic impairment are also recognized. Cyanosis may result in aortopulmonary collateral arteries, hematological abnormalities, renal impairment, and myocardial scarring (6). Collateral arteries may be acquired (e.g., bronchial) or congenital (e.g., complex pulmonary atresia). Cyanosis results in inadequate skin oxygenation, and acne or skin infections are common. This can be important in the context of surgical intervention. Cyanotic patients are frequently small or have an abnormal stature. For personal use only. Decreased Pulmonary Blood Flow In patients with diminished pulmonary blood flow, hypoxemia is minimized by ade- quate hydration, maintaining systemic arterial blood pressure, minimizing elevations in pulmonary vascular resistance (avoiding hypercarbia and acidosis), and minimiz- ing total oxygen consumption. In the presence of a systemic to pulmonary shunt (e.g., modified Blalock Taus- sig), pulmonary blood flow is dependent on the size of the shunt and the pressure gradient across the shunt (i.e., systolic arterial and pulmonary artery pressures). Mixing Lesions and the Balanced Circulation In the situation of mixing of systemic and pulmonary venous blood, the peripheral arterial oxygen saturation is dependent on the pulmonary: systemic flow ratio (QP:QS). This ratio can be estimated from saturation measurements using the equation QP SaO2 − SSVO2 = QS SPVO2 − SPAO2 where SaO2 is the arterial saturation, SSVO2 the systemic venous saturation, SPVO2 the pulmonary venous saturation, and SPAO2 the pulmonary artery saturation. (Note that SPAO2 is the SaO2 in patients with pulmonary blood flow (PBF) supplied through a Blalock Taussig shunt.) In these patients when QP is greater than QS, SaO2 will be higher, but systemic cardiac output will be lower. When QS is greater than QP, systemic saturations will be lower but cardiac output higher. Thus, the systemic saturation can give a useful indication of QP:QS. However, these interpretations are subject to the limitation of knowing or estimating mixed venous oxygen saturations. A low SaO2 might be due to low pulmonary blood flow or there could be high pulmonary blood flow and a low systemic cardiac output with low mixed venous saturations. The relationship
  6. 6. DK091X_C013.qxd 7/2/07 4:56 PM Page 274 274 Barnard Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 FIGURE 1 Arterial oxygen saturation (SaO2) and systemic venous oxygen saturation (SSVO2) as a function of QP:QS for different values of pulmonary venous oxygen saturation (SPVO2). It is often assumed that SaO2 ∼ 75% equates to the ideal QP:QS of ~1:1. This will be the case if there is good sys- temic perfusion (oxygen extraction resulting in SSVO2 ∼ 50%) and normal lung function (SPVO2 ∼ 100%). However, an SaO2 of 75% may represent a QP:QS 1:1 in certain situations. For personal use only. between SaO2 and QP:QS is hyperbolic, whereas that between systemic venous satu- ration (SSVO2) and QP:QS is parabolic (Fig. 1). Elevated QP (and low QS) in a mixing type circulation will be suggested by the clinical picture of high SaO2, systemic hypotension, oliguria, acidosis, and increased serum lactate. A rapidly increasing metabolic acidosis is the first and sometimes dominant sign of pulmonary hyperperfusion. Elevated QP can decrease lung com- pliance, increase airway resistance, and work of breathing, and if left sufficiently long can, at an extreme, result in characteristic histological changes in the pulmonary vasculature (pulmonary vascular disease). Ventricular Function Systolic and diastolic ventricular dysfunctions are not infrequent. Right ventricle dysfunction is seen more commonly than in patients with acquired heart disease. Simple indices of ventricular function (e.g., ejection fraction) can be rendered inad- equate by complex anatomy and loading conditions (7). Reduced ventricular com- pliance is a feature of some right-sided lesions such as Tetralogy of Fallot. An extreme of diastolic dysfunction is known as restrictive ventricular physiology. In this con- dition, due to the low compliance of the right ventricle, the pulmonary valve opens during diastole as a result of atrial contraction. Systemic ventricular impairment may be congenital (systemic right ventricle, hypertrophic cardiomyopathy) or acquired (previous surgery). The hemodynamic impact of dynamic left ventricular outflow obstruction may be reduced by a modest depression of ventricular function. Arrythmias Patients with diastolic dysfunction or restrictive physiology as well as those who have lesions which intrinsically limit ventricular filling (atrial switch procedures for
  7. 7. DK091X_C013.qxd 7/2/07 4:56 PM Page 275 Adult Congenital Heart Disease and the Surgical Patient 275 transposition of great arteries—Mustard, Senning operations) tolerate loss of sinus rhythm or arrhythmias poorly (8). The latter can cause hemodynamic compromise in these patients more rapidly than in patients with acquired heart disease. The phi- losophy of treating arrhythmias is therefore relatively aggressive. An underlying hemodynamic cause (substrate) for the arrhythmia must be sought. Active measures to return sinus rhythm (including early DC cardioversion) are instituted. PSYCHOSOCIAL CONSIDERATIONS Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 Adults with congenital heart disease are a well-informed population who have undergone previous major surgery and numerous hospital admissions. They may be faced with deteriorating cardiac function as young adults. Most patients function psychologically within the normal range, although low self-esteem, insecurity, and feelings of vulnerability occur. Three categories of morbidity are seen in adults with congenital heart disease—psychological, psychiatric, and neuropsychological (abnormalities due to cardiac dysfunction or interventions). Acute illness exacerba- tions can lead to profound psychological disturbances. The consequences of psy- chological problems include a lower proportion competing for higher education, increased unemployment, and many who underachieve due to a lack of self- confidence. Patients exhibit increased dependence on carers and greater immaturity. The effects of chronic illness on activity and social interactions can be pronounced. For personal use only. These effects are sometimes reinforced by inappropriate parental attitudes and “overprotection.” Patients face problems with marriage, financial security, and wor- ries over childbirth. Concern about genetic transmission of congenital defects is an issue when considering reproduction. SPECIFIC LESIONS Tetralogy of Fallot Tetralogy of Fallot is the commonest cyanotic lesion in older patients. It comprises a ventricular septal defect (VSD), aortic overriding of the ventricular septum, and varying right ventricular outflow obstruction. The perimembranous outlet VSD allows right to left and bidirectional shunting and consequent cyanosis. The outflow obstruction results in right ventricular hypertrophy and may be subvalvar (infundibu- lar), valvar, supravalvar (including branch pulmonary artery stenosis), or a combi- nation. There may be a right aortic arch or atrial septal defect (ASD). The aortic annulus and aorta frequently dilate progressively with age. Asmall number of patients have anomalous coronary arteries (e.g., an anomalous left arterior descending (LAD) coronary artery arising from the right coronary artery). Patients who present as adults will usually already have undergone surgery. Unoperated adults largely comprise those with anatomical features unsuitable for repair—usually abnormalities of the pulmonary arteries. Some adult patients will have undergone palliative procedures to improve pulmonary blood flow prior to definitive repair (Table 5). Repair of tetralogy of fallot (TOF) has been performed for over 30 years, conse- quently older patients will be those individuals who underwent the earliest open heart surgery procedures. Repair involves closure of the VSD and relief of the out- flow obstruction. The latter may involve resection of hypertrophic muscle as well as incision and enlargement of the outflow tract with a patch of pericardium or pros- thetic material. If the patch needs to be extended beyond the outflow tract across the
  8. 8. DK091X_C013.qxd 7/2/07 4:56 PM Page 276 276 Barnard TABLE 5 Key Features of the Tetralogy of Fallot Anatomy Anterior and cephalad deviation of the outlet septum Large subaortic VSD Right ventricular outflow obstruction Right ventricular hypertrophy ±Branch pulmonary artery stenosis, ASD, right aortic arch Commonest cyanotic condition Arrhythmias Right bundle branch block Complete heart block Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 Supraventricular and ventricular tachycardias More frequent in the presence of right ventricular failure Palliation Blalock Taussig/modified Blalock Taussig shunt (subclavian to pulmonary artery) Waterston shunt (ascending aorta to right pulmonary artery) Potts shunt (descending aorta to left pulmonary artery) Central or graft shunt (ascending aorta to main pulmonary artery) Brock procedure (infundibular resection and pulmonary valvotomy) Right ventricle to pulmonary artery conduit, leaving VSD alone or repairing with a fenestrated patch Repair Closure VSD Relief RVOTO Infundibular muscle resection Transannular patch For personal use only. Extracardiac conduit Pulmonary valve replacement Outcome 30-yr actuarial survival 8.6% (90% expected) Sudden death 0–6% Complications Arrhythmias Right ventricular outflow tract obstruction Pulmonary and tricuspid regurgitation Diminished RV function Prosthetic complications Residual VSD Abbreviations: VSD, ventricular septal defect; ASD, atrial septal defect; RV, right ventricular. pulmonary valve (transannular), then pulmonary regurgitation is more likely, and homograft replacement of the pulmonary valve may be preferred. Other extracardiac conduits connecting the right ventricle to pulmonary artery are an alternative (e.g., Hancock prosthesis). Transatrial repair of VSDs has diminished myocardial compli- cations from ventriculotomy. Twenty-year survival is 80% to 90%, whereas survival without surgical repair is poor. Postrepair sequelae and residua include rhythm and conduction disorders, recur- rent right ventricular outflow tract obstruction, right ventricular outflow tract aneurysm, recurrent VSD, pulmonary regurgitation, impaired right ventricular function, and tri- cuspid regurgitation. Functional capacity is usually good or normal, and left ventricu- lar function is better with early operation. Reduced exercise ability is related mainly to right ventricular dysfunction consequent to pulmonary regurgitation. Arrhythmias are common. Ventricular ectopics occur in 40% to 50%, and become more frequent with age. A variety of arrhythmias and conduction abnormalities are described, including supraventricular tachycardia, ventricular tachycardia, right bundle branch block, and
  9. 9. DK091X_C013.qxd 7/2/07 4:56 PM Page 277 Adult Congenital Heart Disease and the Surgical Patient 277 complete heart block; 15% of patients demonstrate inducible ventricular tachycardia during electrophysiological studies. The preoperative management of these patients for noncardiac surgery depends on the nature of the repair or palliative operation that they have undergone, the extent of any residual disease, and the sequelae of the condition and of surgery. The clinician should obtain as much information about these as possible. In assessing the patient with repaired tetralogy for noncardiac surgery, the key features to assess are the presence and severity of pulmonary regurgitation, right ventricular function, residual VSD, and arrhythmias. A patient with moder- Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 ate or less pulmonary regurgitation and reasonable right ventricular function is likely to do well and can be managed with standard techniques and monitoring. A patient with significantly impaired right ventricular function needs careful attention to volume status and maintaining contractility. Central venous pressure monitoring is advisable and transesophageal echocardiography is useful for major surgery. Patients with very poor right ventricular function should be referred to a specialist unit. The important aspects of the Tetralogy of Fallot are summarized in Table 5. Atrial Septal Defect ASD is the commonest previously undetected congenital heart lesion in adults. It For personal use only. comprises 7% of congenital heart disease overall, but 30% of adult congenital heart disease. Types include ostium secundum, sinus venosus, and coronary sinus defects. Ostium primum defects are discussed in a later section. They comprise the atrial component of the spectrum of atrioventricular septal defects (AVSDs) and are also referred to as partial AVSD. Ostium secundum accounts for 70% of ASDs and manifests as an absence of the septum in the region of the oval fossa, usually 1 to 2 cm in diameter. It is distinct from patent foramen ovale in that the latter comprises a flap like slit, with no true septal deficiency. Superior sinus venosus defects account for 10% of the total, and occur around the superior atriocaval junction. They are associated with partial anomalous pulmonary venous drainage—usually with the right upper pulmonary veins draining directly into the superior vena cava. Defects occurring near the infe- rior vena cava junction do occur, but are rare. The pathophysiology usually involves a predominant left-to-right shunt. Its magnitude is dependent on the size of the defect, relative ventricular compliances, and the ratio of systemic and pulmonary vascular resistances. The net effect is vol- ume and pressure overload of the right heart, and increased pulmonary blood flow. If untreated, approximately 10% of patients would develop pulmonary vas- cular disease and eventually the Eisenmenger reaction (reversal of shunting con- sequent upon elevated pulmonary vascular resistance). Closure would then be contraindicated. Many patients will be asymptomatic or have subtle clinical signs. However, 70% of patients will be symptomatic by 40 years, and many patients over the age of 60 years will be symptomatic. Symptoms when present consist of palpitations, fatigue, dyspnea, cough, and infection. Chest pain may reflect right ventricular ischemia. There is a preferential streaming of inferior vena caval blood to a secun- dum ASD, which places unoperated patients at risk of paradoxical emboli at any time, even if the shunt is almost entirely left to right. The decline in well being with
  10. 10. DK091X_C013.qxd 7/2/07 4:56 PM Page 278 278 Barnard age may reflect the onset of hypertension and coronary artery disease, which decrease left ventricular compliance and increase left-to-right shunting. Other causes of decreased left ventricular compliance such as mitral stenosis and mitral regurgita- tion will also increase shunt flow. Physical examination demonstrates a prominent right ventricular impulse, loud S1, fixed and widely split S2. An ejection systolic murmur in the pulmonary area and a middiastolic tricuspid murmur are the result of increased (right heart) blood flow. Electrocardiography may show partial or complete right bundle branch block, right axis deviation, and an increased P–R interval. Echocardiography con- Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 firms the presence of a defect, and will often show dilated right atrium and ventricle, and paradoxical atrial septal motion. The incidence of arrhythmias, ventricular dysfunction, and pulmonary vascu- lar disease are related to the age at closure. If there are no arrhythmias prior to clo- sure, there is a 5% to 10% late incidence of arrhythmias, whereas patients with a significant defect who exhibit arrhythmias preclosure virtually all have recurrent arrhythmias by 25 years. Thirty percent of patients with preoperative atrial fibrilla- tion will retain sinus rhythm at late follow-up. Tachyarrhythmias become increas- ingly common after the fourth decade. If surgical repair is delayed (e.g., beyond 40 years), elevation in pulmonary artery pressures may be observed. Owing to left ventricular volume and geometry changes, there is a small incidence of mitral regurgitation in adults with secundum For personal use only. ASD. If operation is carried out prior to 20 years of age in the presence of normal pulmonary vascular resistance, survival is the same as controls. These patients can effectively be treated as if they did not have congenital heart disease. Age at opera- tion can affect (right) ventricular function. Similarly, ventricular end diastolic pres- sure increases in a minority of patients who undergo repair as adults, but those operated on when children do not exhibit left ventricular dysfunction. Interestingly, the indications for repair continue to be debated. Traditionally intervention is advised if there is a significant left-to-right shunt (QP:QS more than 1.5:1) in order to avoid arrhythmias, infective endocarditis, pulmonary hyperten- sion, and increased mortality. Modern echocardiographic techniques have improved detection of smaller defects in asymptomatic patients. Previous outcome data may not apply to this group, and at least one long-term follow-up of asymptomatic patients compared well with surgical treatment. In general, closure is advised for a “signifi- cant” defect which is defined as volume or pressure overload, exercise limitation, atrial arrhythmias, late right heart failure, or paradoxical embolism. Transcatheter device closure is now routine. It is suitable for secundum defects less than approximately 30 mm, with a rim around the defect. Long-term compar- isons of outcome with surgery are awaited. Endocarditis prophylaxis is not subse- quently required. Implications of nonoperated ASD include paradoxical embolism and elevated work of breathing due to decreased lung compliance. Late atrial arrhythmias may occur, and right heart failure or pulmonary vascular disease occurs in approxi- mately 10%. Patients who have undergone surgical closure should present few problems when undergoing noncardiac surgery, with arrhythmias being the commonest com- plication. Patients who have not undergone closure should be managed as normal, with specific attention paid to endocarditis prophylaxis and prevention of paradoxi- cal embolism. Volume status should be maintained, to avoid increasing the magnitude of shunting. Theoretically, changes in pulmonary and systemic vascular resistance can
  11. 11. DK091X_C013.qxd 7/2/07 4:56 PM Page 279 Adult Congenital Heart Disease and the Surgical Patient 279 alter the magnitude or even direction of shunting, but in the experience of this author this is of little clinical significance, because such alterations would have to be enor- mous to produce noticeable effects. Transposition of the Great Arteries Transposition of the great arteries (TGA) is defined as atrioventricular concordance and ventriculoarterial discordance—put simply, the atria are connected to the appro- priate ventricle but the ventricles are connected to the “opposite” great artery. The Heart Disease and The Surgical Patient Downloaded from by HINARI on 07/17/10 aorta arises from the anatomical right ventricle and the pulmonary artery arises from the anatomical left ventricle. Blood flow, therefore, occurs in two parallel circulations rather than the normal series arrangement. Maintenance of life depends on a degree of mixing of oxygenated and deoxygenated blood between the two circulations. This can occur through an atrial or VSD, patent arterial duct, or atrial septostomy. Pallia- tive intervention in the newborn to achieve mixing was originally achieved surgically (Blalock Hanlon septostomy) and subsequently by percutaneous balloon atrial sep- tostomy (Rashkind). TGA is described as simple in the presence of an intact ventric- ular septum. Complex TGA involves the combination of TGA with VSD and possibly other abnormalities. The pulmonary artery overrides the ventricular septum, and if more than 50% is committed to the left ventricle the abnormality may be described as TGA with VSD, whereas if more than 50% of the pulmonary artery is committed to For personal use only. the right ventricle the correct terminology is double outlet right ventricle. Overall, 75% of TGA lesions are simple, 20% are combined with VSD, and 5% of patients have TGA with subpulmonary stenosis. Up to 28% demonstrate anomalies of the coronary arteries, which is important for surgical intervention in childhood. TGA with VSD may be associated with unobstructed outflow; alternatively, deviation of the outlet septum causes outflow tract obstruction. Posterior deviation of the outlet septum restricts pulmonary blood flow, whereas anterior deviation results in subaortic stenosis. Complex TGA with subpulmonary stenosis presents early in life with severe cyanosis due to decreased pulmonary blood flow. Complex TGA with unobstructed aortic flow leads to gradual development of heart failure and may present later. Adults with this circulation will usually have previously undergone surgery. Very occasionally a degree of subpulmonary stenosis can result in balanced flow which is compatible to survival to adult life without surgery. Surgical interventions are varied and have altered in response to the development of late complications. Simple TGA was originally and successfully treated with atrial redirection (atrial switch) operations, the Senning and Mustard procedures. These procedures redirect blood within the atria to the opposite ventricle, resulting in physiologically appro- priate circulation pathways. The Rastelli operation was originally introduced for TGA, VSD, and left ventricular outflow obstruction (subpulmonary stenosis). It involves closing the VSD and thereby tunneling left ventricular blood to the aorta. Right ventricle to pulmonary artery continuity is achieved by placing a valved con- duit between the two. The arterial switch operation involves transecting the aorta and pulmonary arteries and reconnecting them to the appropriate ventricle. The atrial or arterial switch procedures can be combined with VSD closure in the context of TGA, VSD, and unobstructed aortic flow. Finally, palliative atrial procedures involve redirection of blood at atrial level, while retaining or creating a VSD. This has been used in those patients who are unsuitable for physiological repair, usually because of pulmonary vascular abnormalities.