11 Heart Failure Caused by Congenital Heart Disease
Basic Principles
Key Points
• Heart failure occurs frequently in children with congenital heart disease (CHD) and is often an indication for intervention.
• In contrast to adult heart failure, which is often caused by decreased coronary perfusion, children with CHD typically develop heart failure as a result of the underlying cardiac defect or in association with congenital heart surgery.
• Commonly used measures of ventricular performance (Table 11-1) are limited because they are preload and/or afterload dependent. However, in serial assessment of function, these methods are useful clinically.
• Newer echocardiographic modalities to assess ventricular performance (such as strain and strain-rate imaging) are challenging in the CHD population because of the abnormal anatomy.
TABLE 11-1 ECHOCARDIOGRAPHIC INDICES OF VENTRICULAR PERFORMANCE
| Shortening fraction (SF) |  |
| Ejection fraction (EF) |  |
| Heart rate corrected mean velocity of circumferential fiber shortening (Vcfc) |   |
| End-systolic wall stress (ESWS) |  |
| Myocardial performance index (MPI) |  |
The Causes of Heart Failure in CHD
Left-to-Right Shunts
• Left-to-right shunt lesions comprise the most common congenital cardiac anomalies in children, excluding bicuspid aortic valve (Box 11-1), and are the most common cause of high-output heart failure.
• Newborn infants with significant left-to-right shunts are typically asymptomatic at birth as a result of high pulmonary vascular resistance. If a left-to-right shunt is large (i.e., a large ventricular septal defect), symptoms usually develop by 4 to 8 weeks of age when the pulmonary vascular resistance normalizes.
• Over this time period, pulmonary blood flow increases, resulting in symptoms that include tachypnea, tachycardia, failure to gain weight, and diaphoresis with feedings. Feeding is a form of exercise for the newborn, thus nursing or bottle-feeding in a child with a large left-to-right shunt will often result in a catecholamine surge.
• As a rule, surgical repair of left-to-right shunts alleviates the heart failure and growth resumes.
Key Points
• Echocardiography of left-to-right shunts will identify the lesion in multiple views (Figure 11-1).
• If the shunt is large, the pressure in the right and left ventricles will be equal and Doppler color interrogation will demonstrate laminar flow (see Figure 11-1).
• Other indicators of a chronic, large shunt will include chamber dilatation, generally best seen in the subxiphoid and apical 4-chamber views (see Video 11-1 on the Expert Consult website). In ventricular septal defect, common atrioventricular canal defect, truncus arteriosus, and patent ductus arteriosus, the left atrium and left ventricle dilate because of left ventricular volume overload.
• Right ventricular pressure will be systemic or near-systemic with a large left-to-right shunt and can be measured from the tricuspid regurgitation jet or from the velocity across the ventricular septal defect.
• Ventricular systolic performance is typically hyperdynamic (as measured by shortening fraction or ejection fraction) to compensate for the high cardiac output. If left unrepaired for a long time, ventricular dysfunction may occur.
Left Heart Obstructive Lesions
• Left ventricular systolic dysfunction is seen with higher frequency in certain congenital heart lesions, such as left heart obstructive lesions (Box 11-2).
• The pressure load associated with these obstructive lesions results in ventricular hypertrophy, elevated end-diastolic pressure and eventual systolic and diastolic dysfunction.
• Critical left heart obstruction is a newborn diagnosis, defined as obstruction that is so severe that the infant is dependent on flow from the ductus arteriosus to augment cardiac output. Neonates with critical left heart obstruction require urgent surgical or catheter-directed intervention.
• Left ventricular failure is a component of the diagnosis because of significant pressure overload from the diminutive aortic valve orifice (Figure 11-2; also see Video 11-2 on the Expert Consult website). In addition, some infants with critical aortic stenosis have marked mitral regurgitation, which adds a volume load to the already pressure-loaded left ventricle (see Video 11-2 on the Expert Consult website).
• Critical aortic stenosis is often associated with endocardial fibroelastosis. Endocardial fibroelastosis is a poorly understood phenomenon whereby the left ventricular endocardium becomes fibrotic, likely as a result of long-standing subendocardial ischemia (Figure 11-3; also see Video 11-3 on the Expert Consult website). Children with endocardial fibroelastosis have poor ventricular systolic shortening and high end-diastolic and left atrial pressure, even after the aortic stenosis is relieved.
• After intervention, these infants may remain quite ill because of residual outflow obstruction, poor left ventricular function or the development of new-onset aortic regurgitation as a complication of the intervention.
• Intervention for aortic stenosis in later infancy or childhood tends to have better outcome because the left ventricle has responded over time to the pressure load by developing hypertrophy.
Figure 11-3 Apical 4-chamber view in the same patient as Figure 11-2 with critical aortic stenosis demonstrates a dilated but hypoplastic left ventricle (non–apex forming), with echo-bright papillary muscles consistent with endocardial fibroelastosis. Color Doppler demonstrates mitral regurgitation.
Key Points
• Endocardial fibroelastosis can often be visualized in multiple views, but the sonographer must be cautioned not to mistake increased gain for this disorder.
• In critical aortic stenosis, it must be recognized that the peak instantaneous velocity across the stenotic aortic valve may not be particularly high if there is severe left ventricular dysfunction, because the ventricle cannot generate high pressure (Figure 11-4).
• Additional echocardiographic evidence of low cardiac output is a shortened ejection time using pulsed wave Doppler.
• In critical left heart disease, the ductus arteriosus flow pattern will be right to left in systole to augment cardiac output from the right ventricle.
• Adolescents and young adults who had critical aortic stenosis in association with endocardial fibroelastosis as infants may continue to show evidence of significant cardiac disease, which may be manifested as restrictive cardiomyopathy (Figure 11-5; also see Video 11-4 on the Expert Consult website).
The Systemic Right Ventricle
• Certain forms of CHD, both palliated and unpalliated, result in the right ventricle supporting the systemic circulation.
• Early in life, most children with a systemic right ventricle compensate well; however, ventricular failure is common in adolescence and adulthood.
• Prior to surgical intervention, the most common cardiac lesion with a systemic right ventricle is congenitally corrected transposition of the great arteries (cc-TGA). cc-TGA is defined as discordant atrioventricular as well as ventriculo-arterial connections such that the right atrium connects to the left ventricle, from which the pulmonary artery arises, and the left atrium connects to the right ventricle, from which the aorta arises (most commonly the aorta is positioned anterior and to the left of the pulmonary artery) (Figure 11-6A; also see Video 11-5 on the Expert Consult website). The circulation remains in series (thus the term “congenitally corrected”), and rarely patients with the simple form of this defect (no additional cardiac anomalies) go unrecognized until adolescence or adulthood because they are initially asymptomatic.
• cc-TGA is frequently associated with Ebstein-like malformation of the tricuspid valve and associated tricuspid regurgitation (see Figure 11-6; see also Video 11-5 on the Expert Consult website). In the more complex form of cc-TGA, additional cardiac defects are common, such as ventricular septal defect, pulmonary outflow obstruction, or systemic outflow obstruction. These findings lead to early clinical presentation.
• The natural history of cc-TGA is variable, with right ventricular failure being the most common presentation. Significant tricuspid regurgitation may accelerate the development of ventricular dysfunction. By the third decade of life, most patients with cc-TGA will have systemic right ventricular failure with decreased exercise capacity on exercise stress testing and advanced New York Heart Association (NYHA) functional classification status.
• Those with additional cardiac defects (e.g., ventricular septal defect, outflow obstruction) develop heart failure and exercise intolerance earlier than those with the simple form.
• Similar findings occur in patients with the more common form of transposition of the great arteries (TGA), whereby there is atrioventricular concordance and ventriculo-arterial discordance.
• In the late 1950s through the early 1980s, the primary surgical procedure for TGA was an atrial switch procedure (Senning or Mustard); the atrial switch baffles blood flow at the atrial level with a systemic venous pathway to the mitral valve and a pulmonary venous pathway to the tricuspid valve. This procedure changes the parallel circulation to one in series (Figure 11-7; also see Video 11-6 on the Expert Consult website).
• The long-term consequence of the atrial switch operation is that the right ventricle must support the systemic circulation. With long-term follow-up of these patients, it has recently become clear that right ventricular failure is common in this population, similar to those individuals with cc-TGA.
• The etiology of right heart failure in both cc-TGA and TGA after the atrial switch operation is poorly understood. The morphology of the right ventricle may in part account for the right ventricular failure that develops. Muscle fiber orientation is different in the two ventricles. In those patients with significant tricuspid regurgitation, the volume load burdens the right ventricle and likely leads to decreased systolic and diastolic performance.
• Some studies suggest that low-grade coronary insufficiency occurs in the systemic right ventricle. This has been supported by studies of myocardial perfusion that have shown myocardial fibrosis and regional wall motion abnormalities in these patients.
• Arrhythmias are commonly associated with these cardiac lesions. Patients with cc-TGA have a 2% annual risk for the development of complete heart block, which may cause cardiac dyssynchrony and heart failure.
• Atrial arrhythmias such as sick sinus syndrome, atrial flutter, and atrial fibrillation are common after the atrial switch procedure. Pacemakers are frequently implanted in this patient population, and this abnormal conduction pathway may be associated with decreased right ventricular function.
• Treatment of heart failure in patients with systemic right ventricles is challenging as there are no specific medical therapies that target the right ventricle.
• As a result of poor long-term outcome in unrepaired cc-TGA, some advocate for the “double switch” operation; this procedure includes an atrial and arterial switch such that the left ventricle becomes the systemic ventricle. The left ventricle often has to be “prepared” for such a procedure by performing a pulmonary artery banding to achieve systemic pressure in the left ventricle.
• The operative mortality for late “double switch” operation is approximately 5% to 6%. Complications may occur from both procedures, including atrial arrhythmias, atrial baffle obstruction and/or baffle leak, left ventricular failure, coronary perfusion abnormalities, and outflow tract obstruction. In some cases, cardiac transplantation becomes the best option if severe heart failure develops.
Key Points
• Echocardiography of the systemic right ventricle is challenging. In contrast to the left ventricle, there are no standard methods for assessing right ventricular performance in this setting.
• Subjective assessment remains the most common method used in echocardiography laboratories. This method is quick and easy to perform, particularly with user experience, but is confounded with regard to interobserver variability and reproducibility.
• Percent fractional area change is a quantitative measure of right ventricular performance. This method is similar to ejection fraction except it uses a planimetric technique to measure right ventricular end-diastolic and end-systolic area. Fractional area change less than 40% is considered abnormal.
• Myocardial performance index (MPI), a measure of global systolic and diastolic function, can be used to assess systemic right ventricular performance. The isovolumic relaxation and contraction time intervals are divided by the ejection time, with a higher MPI indicating worse overall ventricular performance (see Table 11-1). Using MPI to assess right ventricular function has resulted in conflicting data. In addition, MPI may not correlate with right ventricular dysfunction, particularly when there are regional wall motion abnormalities.
• Tricuspid annular plane systolic excursion (TAPSE) has been found to correlate with cardiac magnetic resonance imaging (CMRI)–derived right ventricular ejection fractions in some patients with systemic right ventricles (pulmonary artery hypertension) but also has limited use in patients with regional wall motion abnormalities. It primarily measures longitudinal shortening of the right ventricle (Figure 11-8).
The Single Ventricle
• A variety of congenital heart defects comprise the functional single ventricle, including most commonly hypoplastic left heart syndrome, hypoplastic right heart, tricuspid atresia, and double inlet ventricle.
• After initial surgery (depending on the underlying anatomy), patients undergo staged palliation that culminates in the total cavopulmonary anastomosis procedure known as the Fontan operation (Figure 11-9; also see Video 11-7 on the Expert Consult website). In this palliative procedure, the systemic venous blood bypasses the heart and is connected directly to the pulmonary arteries, such that blood flows passively across the pulmonary vascular bed. The single ventricle is thus dedicated to providing the systemic circulation.
• Diastolic dysfunction is common after the Fontan procedure for single-ventricle lesions. Prior to the era of staging with the bidirectional cavopulmonary shunt, children who underwent the Fontan operation often had significant morbidity, including recalcitrant pleural effusions, ascites, electrolyte abnormalities, and low cardiac output. Echocardiographic assessment in these patients often reveals a ventricle with diminished end-diastolic volume, relaxation abnormalities, and increased ventricular mass in association with good systolic performance.
• The “volume unloading” that occurs with the Fontan procedure results in increased ventricular mass that regresses slowly over time. By staging the Fontan procedure with the interim bidirectional cavopulmonary shunt, the single ventricle adapts over time to the changes in volume with an adequate output to the body via the inferior vena cava.
• In general, children who have had the Fontan operation have lower cardiac output and poorer exercise performance than those with a biventricular circulation. Early- and late-onset heart failure is a common problem after the Fontan operation and can be a result of systolic and/or diastolic dysfunction.
• The ventricle may sustain injury from one of the surgical procedures or from other residual or recurrent cardiac problems (e.g., coarctation of the aorta, significant atrioventricular or semilunar valve regurgitation).
• High filling pressure in the systemic ventricle leads to high Fontan baffle pressure (and thus high systemic venous pressure). Symptoms may include plethora, exercise intolerance, edema, recalcitrant pleural effusions, and hepatic dysfunction.
• Patients who have undergone the Fontan procedure are also at risk for arrhythmias that may affect cardiac performance. Junctional rhythm is common after surgery, and cardiac index may decrease without atrial contraction. Atrial flutter and fibrillation may also occur and impact adversely on ventricular function.
• Few therapies exist for heart failure in association with a functional single ventricle. Routine medical therapies such as afterload reduction and inotropes may be effective. Carvedilol has been effective in the treatment of heart failure in some patients with single ventricle. Even cardiac resynchronization has been attempted in the subset of patients with dyssynchrony. Cardiac transplantation is the only known effective long-term therapy.
Key Points
• Echocardiographic imaging of the single ventricle has challenges similar to those with the systemic right ventricle. Moreover, the ventriculo-ventricular interactions observed in hearts with two ventricles are often not present.
• Subjective evaluation of dysfunction remains the most common method of assessment, although the techniques described for systemic right ventricle are being utilized in the single-ventricle population as well. MPI in patients with single right ventricles has been reported as significantly higher compared to that in normal subjects.
• In patients with fenestrated Fontan baffles, the trans-fenestration gradient can be estimated by Doppler assessment of the mean velocity across the fenestration (Figure 11-10). A higher trans-fenestration mean gradient may indicate high Fontan baffle pressures.
Coronary Insufficiency
• Although unusual in the pediatric population, coronary insufficiency and subsequent heart failure do occur in a subset of congenital heart defects that affect the coronary arteries.
• Anomalous left coronary artery from the pulmonary artery (ALCAPA) is the most common of these lesions. In this defect, the left coronary artery arises from the pulmonary artery instead of the aorta. After pulmonary vascular resistance falls in the neonatal period, a “steal” phenomenon occurs such that blood flows from the left ventricular myocardium into the pulmonary artery. Myocardial ischemia and infarction occur as a result of this coronary insufficiency. The echocardiographic presentation is consistent with endocardial fibroelastosis with echo-bright endocardium and mitral valve dysfunction (Figure 11-11).
• Infants with ALCAPA typically present at 6 to 10 weeks of age with profound heart failure. The most common albeit pathognomonic symptom is irritability and sometimes loss of consciousness with exertion (feeding).
• The arterial switch operation performed in patients with TGA may compromise coronary perfusion because the coronary arteries must be transferred to the neo-aorta.
• Some coronary variations in TGA, including single coronary anatomy and, in particular, coronaries that take an intramural course, are associated with left ventricular dysfunction after the arterial switch operation.
• Coronary insufficiency may occur early at the time of surgical repair or late in adolescent years. The presentation may be similar to myocardial infarction in adults, in whom sudden death can be the presenting symptom.
• Routine assessment for coronary insufficiency in children who have had coronary reimplantation is controversial. If coronary insufficiency is identified, surgical coronary reintervention is usually indicated to preserve ventricular performance. Sudden death is rare but can occur in this population of patients.
Key Points
• Echocardiography of an infant with ALCAPA and heart failure typically demonstrates a markedly dilated and poorly functioning ventricle with echo-bright endocardium and papillary muscles. Significant mitral regurgitation is common from the papillary muscle dysfunction (see Figure 11-11).
• Echocardiographic assessment of the origin of the left coronary artery can be challenging; in ALCAPA, the left coronary artery may appear to arise normally from the aorta (Figure 11-12).
• In many cases, the anomalous connection to the pulmonary artery can be visualized with retrograde flow into the main pulmonary artery. If all other findings point to ALCAPA but the coronary origin is not well seen, cardiac catheterization may be required to make the diagnosis.
• Coronary ischemia after the arterial switch operation is typically manifest as regional wall motion abnormalities or global left ventricular dysfunction.
• Assessment of coronary perfusion after the arterial switch operation typically requires modalities other than echocardiography, such as cardiac catheterization, CMRI, and stress echocardiography to assess myocardial perfusion.
Left Ventricular Dysfunction after Biventricular Repair
• Biventricular repair is performed for a variety of congenital heart defects, including ventricular septal defect, tetralogy of Fallot (TOF), common atrioventricular canal defect, double-outlet ventricle, and truncus arteriosus. Left ventricular dysfunction and heart failure may occur early or late after repair.
• Patients with tetralogy of Fallot or truncus arteriosus may develop late-onset left ventricular failure. This is poorly understood but likely related to ventriculo-ventricular interactions and conduction abnormalities.
• The right ventricle is typically exposed to a significant volume load (pulmonary regurgitation) after repair, resulting in significant dilatation and eventually systolic dysfunction (Figure 11-13; also see Videos 11-8A and 11-8B on the Expert Consult website). Left ventricular dysfunction may occur after long-standing right ventricular dilatation and dysfunction.
• Valvuloplasties and valve replacements may also be associated with left ventricular dysfunction and heart failure after surgery.
• Significant mitral regurgitation increases preload to the left ventricle; at the same time, afterload is decreased as the blood empties into the left atrium. Eventually irreversible myocardial damage develops.
• It is often a challenge to determine the ideal timing for mitral valvuloplasty or replacement because left ventricular dysfunction may not become evident until after surgery. Repair of mitral regurgitation results in an acute increase in afterload to the left ventricle. As a result, mitral valvuloplasty and/or replacement continue to have a relatively high morbidity and mortality when compared to other congenital heart defect surgeries.
Key Points
• Strain and strain-rate imaging can be used to detect subtle changes in left ventricular performance in patients with TOF. Moreover, left ventricular dyssynchrony and abnormal strain may occur after TOF repair in association with prolonged QRS complex duration on electrocardiogram.
• Echocardiographic indices of dysfunction prior to atrioventricular valve intervention have been challenging in both the pediatric and adult population. The decreased afterload associated with significant mitral regurgitation may mask ventricular dysfunction. Serial echocardiography to assess left ventricular end-diastolic and end-systolic volume changes is helpful in clinical decision making.
• In a patient with normal myocardium, the systolic performance should be hyperdynamic. If ejection fraction decreases over serial assessments (even if still in the normal range), intervention may be necessary to prevent the development of significant left ventricular dysfunction and heart failure after surgery.
When Are Other Diagnostic Tests Needed?
• There are significant limitations to the use of echocardiography in the detection of heart failure in the setting of CHD, particularly in the assessment of right ventricular function and in the detection of subtle abnormalities in left ventricular performance.
• CMRI provides accurate quantitative information on ventricular performance in children with CHD; this includes measures of ejection fraction, regurgitant fraction, ventricular volumes, and, when appropriate, cardiac index. In addition, CMRI can also be used to assess myocardial viability (Figure 11-14). New techniques have recently been developed to assess ventricular performance and viability during exercise; some CMRI scanners have exercise bicycle equipment for this purpose.
• Cardiac computed tomographic imaging provides some information similar to that from CMRI and requires shorter periods in the scanner. However, there is radiation risk to the patient, particularly if performed multiple times.
• Cardiac catheterization remains the only diagnostic test that accurately measures end-diastolic pressure.
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