Tetralogy of Fallot (TOF) is the most common cyanotic heart disease seen in adulthood, and it represents 10% of congenital heart defects.
It consists of a large VSD, pulmonary stenosis (which may be valvular, subvalvular, and or supravalvular), an aorta that overrides the VSD, and RV hypertrophy.
Pathology
Newborns with TOF are cyanotic because of the right-to-left shunt through the VSD and decreased pulmonary blood flow. The amount of pulmonary blood flow depends on the severity of the obstruction through the RV outflow tract. By the time TOF patients reach adult- hood, most have had complete repair or palliative surgery.
Many adults with repaired TOF have had a transannular patch (i.e., synthetic patch across the pulmonary annulus) placed to relieve the RV outflow tract obstruction. This patch causes obligatory free pul- monary regurgitation. Free pulmonary regurgitation can be well tol- erated by the right ventricle for many years, but usually in the third or fourth decades, the right ventricle begins to dilate, and it may become dysfunctional. Significant RV dilation and dysfunction can lead to LV dysfunction, significant tricuspid regurgitation, and atrial or ventricu- lar arrhythmias. Almost 29% of adults with repaired TOF also have a dilated ascending aorta due to increased blood flow through the aorta before repair.
Clinical Presentation
Patients with repaired TOF typically have normal oxygen saturation levels. On palpation, there often is an RV lift at the left lower sternal border. On auscultation, there typically is a widely split second heart sound with a to-and-fro murmur in the pulmonary area due to signif- icant pulmonary regurgitation or, less commonly, aortic regurgitation.
A holosystolic murmur due to tricuspid regurgitation may be heard at the left lower sternal border. Symptoms in the adult with repaired TOF may include exertional dyspnea, palpitations, syncope, and sud- den cardiac death.
Diagnosis
The ECG almost universally reveals a right bundle branch block pat- tern in patients who underwent repair of TOF. The QRS duration from the standard surface ECG correlates with the degree of RV dilation and dysfunction. A maximum QRS duration of 180 milliseconds or more is a highly sensitive and relatively specific marker for sustained ventric- ular tachycardia and sudden cardiac death. Patients with significant pulmonary regurgitation often have cardiomegaly with dilated central pulmonary arteries identified on the chest radiograph. A right aortic arch occurs in 25% of cases, and it can be detected by close observation of the chest radiograph. An echocardiogram is useful for evaluating the RV outflow tract (e.g., pulmonary regurgitation, residual stenosis), biventricular size and function, tricuspid valve function, and ascending aortic size. MRI is the gold standard for assessing RV size and function
(Fig. 6.2). It can also give an accurate assessment of the degree of pul- monary insufficiency and branch pulmonary artery anatomy.
Treatment
Treatment for TOF is surgical repair. Repair is typically performed between 3 to 12 months of age and consists of patch closure of the VSD and relief of the pulmonary outflow tract obstruction by patch augmen- tation of the RV outflow tract or pulmonary valve annulus, or both.
Reintervention is necessary in approximately 10% of adults with repaired TOF after 20 years of follow-up. With longer follow-up, the incidence of reintervention continues to increase. The most common indication for reintervention is pulmonary valve replacement in patients with moder- ate or greater pulmonary valve regurgitation and symptoms. Pulmonary valve replacement is also reasonable for preservation of ventricular size and function in asymptomatic patients with repaired tetralogy of Fallot and ventricular enlargement or dysfunction and moderate or greater pul- monary regurgitation. Pulmonary valve replacement can be performed surgically, or in some patients, percutaneously. Patients with repaired tetralogy of Fallot may be considered for an ICD for primary prevention if multiple risk factors for sudden death are present, including LV sys- tolic or diastolic dysfunction, nonsustained ventricular tachycardia, QRS greater than 180 ms, extensive right ventricular scarring or inducible sus- tained ventricular tachycardia at an electrophysiologic study.
Prognosis
In the developed world, the unoperated adult with TOF has become a rarity because most patients undergo palliation (i.e., stenting) or repair in childhood. Survival of the unoperated patient to the seventh decade has been described but is rare. Only 11% of unrepaired patients are alive at 20 years of age and only 3% at 40 years.
Late survival after repair of TOF is excellent. Survival rates at 32 and 35 years are 86% and 85%, respectively, compared with 95% for age- and sex-matched controls. Importantly, most patients live an unrestricted life. However, many patients over time develop late symptoms related to numerous, long-term complications after TOF repair. Late complications include endocarditis, aortic regurgitation with or without aortic root dila- tion (typically due to damage of the aortic valve during VSD closure or to an intrinsic aortic root abnormality), LV dysfunction (from inadequate myocardial protection during previous repair or chronic LV volume over- load due to long-standing palliative arterial shunts), residual pulmonary obstruction, residual pulmonary valve regurgitation, RV dysfunction (due to pulmonary regurgitation or pulmonary stenosis), atrial arrhythmias (typically atrial flutter), ventricular arrhythmias, and heart block.
Transposition of the Great Arteries
Definition and EpidemiologyTransposition of the great arteries (TGA) represents 3.8% of all con- genital heart disease. In complete TGA, the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. As a result, the systemic venous flow (i.e., blood with low oxygen content) is returned to the right ventricle and is then pumped to the body through the aorta without passing through the lungs for gas exchange. The pulmonary venous flow (i.e., oxygenated blood) returning to the left ventricle is then pumped back to the lungs. As a result, the systemic and pulmonary circulations run in parallel. Oxygenation and survival depend on mixing between the systemic and pulmonary circulations at the atrial, ventricular, or PDA level. In 50% of cases, there are other anomalies: VSD (30%), pulmonary stenosis (5% to 10%), aortic steno- sis, and coarctation of the aorta (≤5%).
The first definitive operations for TGA (i.e., atrial switch proce- dures) were described by Senning in 1959 and Mustard in 1964. In these procedures, the systemic and pulmonary venous returns are
rerouted in the atrium by constructing baffles. The systemic venous return from the superior and inferior vena cavae is directed through the mitral valve and into the left ventricle, which is connected to the pulmonary artery. The pulmonary venous return is then directed through the tricuspid valve into the right ventricle, which is connected to the aorta. These procedures leave the left ventricle as the pulmonary ventricle and the right ventricle as the systemic ventricle.
Over the past 20 years, the arterial switch procedure has gained popularity. During the procedure, the great arteries are transected and reanastomosed to the correct ventricle (i.e., left ventricle to the aorta and right ventricle to the pulmonary artery) along with coronary artery transfer. Operative survival after the arterial switch procedure is very good, with a surgical mortality rate of 2% to 5%.
Pathology
Most infants who do not have surgical intervention die in the first few months of life. For adults born with complete TGA who have had an atrial switch procedure, the right ventricle continues to be the systemic ventricle, and the left ventricle is the subpulmonic ventricle. Long- term follow-up series have demonstrated that the right ventricle can function as the systemic ventricle for 30 to 40 years, but with longer follow-up, systemic ventricular dysfunction continues to increase. At the 35-year follow-up, approximately 61% of patients have developed moderate or severe RV dysfunction.
Another common postoperative problem is the tricuspid valve.
After the atrial switch procedure, the tricuspid valve remains the sys- temic atrioventricular valve and must tolerate systemic pressures. Due to changes in RV morphology and abnormal chordal attachments, the tricuspid valve is prone to become dysfunctional and develop signifi- cant regurgitation.
Significant coronary lesions, such as occlusions or stenoses, occur in 6.8% of patients who have had the arterial switch procedure. These lesions are likely related to suture lines or kinking at the time of reim- plantation of the coronary arteries into the neo-aorta. Systemic LV function is usually normal. LV dysfunction is associated with coronary anomalies.
Clinical Presentation
In the repaired adult with an atrial switch procedure, the physical examination may reveal a murmur consistent with tricuspid valve insufficiency and a prominent second heart sound due to the anterior
position of the aorta. Patients who have had an atrial switch procedure tend to have worsening functional status as the length of follow-up increases. They often have resting sinus bradycardia or a junctional rhythm. Palpitations due to atrial arrhythmias are common, occurring in up to 48% of patients 23 years after the atrial switch procedure.
In those who undergo the arterial switch procedure, the physical examination may reveal a murmur of neo-aortic or neo-pulmonic regurgitation. These patients usually have normal function status, but because of denervation of the heart, myocardial ischemia may manifest as atypical chest discomfort.
Diagnosis
After the atrial switch procedure, the ECG may show a loss of sinus rhythm with evidence of RV hypertrophy. Ambulatory monitors are important to monitor for bradyarrhythmias, sinus node dysfunction, and atrial arrhythmias. Chest radiographs may show an enlarged car- diac silhouette in those with a dilated systemic right ventricle. An echo- cardiogram can demonstrate qualitative systemic RV size and function and the degree of tricuspid regurgitation. MRI is often used to accu- rately quantify systemic RV size and function, tricuspid valve function, and atrial baffle anatomy.
After the arterial switch, echocardiography is used to assess pul- monary artery and branch pulmonary artery stenosis, neo-aortic and neo-pulmonic valve regurgitation, and ventricular function. MRI or computed tomography may be used to assess the anatomy of the branch pulmonary arteries. An exercise stress test is often used to eval- uate myocardial ischemia.
Treatment
Treatment options are limited for adults with complete TGA repaired by atrial switch who have failing systemic right ventricles or significant tricuspid regurgitation, and evidence of significant benefit is lacking.
However, potential treatments include medical therapy, revision of atrial baffles, pulmonary artery banding, resynchronization therapy, ventricular assist devices, and possible transplantation. Medical ther- apy, including consideration of anticoagulation, in patients with atrial tachyarrhythmias is recommended.
After the arterial switch procedure, catheter-based or surgical rein- tervention for pulmonary artery stenosis may be required in 5% to 25% of patients. Coronary artery revascularization is rarely required (0.46% of patients), as is neo-aortic valve repair or replacement (1.1%
Fig. 6.2 Short axis magnetic resonance images of the right and left ventricles with epicardial and endocar- dial tracings of both ventricular cavities. There are a predefined number of slices through the heart with a constant thickness. The volumes of the left and right ventricles in each slice are calculated and summed together in end diastole and end systole to determine the total right and left ventricular volumes (i.e., Simp- son’s method).
63 CHAPTER 6 Congenital Heart Disease
of patients). Guideline-directed recommendations for aortic valve replacement are reasonable to follow for patients with d-TGA and severe neo-aortic valve regurgitation.
Prognosis
Long-term follow-up studies after the atrial switch procedure show a small but ongoing attrition rate, with numerous intermediate- and long-term complications. Long-term complications include systemic RV dysfunction and tricuspid valve regurgitation, loss of sinus rhythm with the development of atrial arrhythmias (50% incidence by age 25), endocarditis, baffle leaks, baffle obstruction, and sinus node dysfunc- tion requiring pacemaker placement. Intermediate-term complica- tions related to the arterial switch procedure include coronary artery compromise, pulmonary outflow tract obstruction (at the supraval- vular level or takeoff of the peripheral pulmonary arteries), neo-aortic valve regurgitation, endocarditis, and neo-aorta dilation.
As a result of the long-term complications associated with the atrial switch procedure, the arterial switch operation has been the procedure of choice since 1985. Long-term data on the survival after the arterial switch operation do not exist, but intermediate-term results are prom- ising: 88% at 10 and 15 years.
For a deeper discussion on this topic, please see Chapter 61,
“Congenital Heart Disease in Adults,” in Goldman-Cecil Medicine, 26th Edition.
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64
Valvular Heart Disease
Christopher Song
INTRODUCTION
In developing countries, rheumatic heart disease (RHD) remains a common cause of valvular heart disease (VHD). In industrialized countries, the burden of rheumatic disease has significantly decreased, and the most common etiology is degenerative disease. The prevalence of VHD in the US adult population is 2.5%. Prevalence increases with age to as high as 13.3% in those 75 years and older. Moderate or severe VHD is associated with excess mortality. Therefore, with an aging pop- ulation, valvular heart disease is and will continue to be a major public health problem.
The “2014 AHA/ACC Guideline for the Management of Patients with Valvular Heart Disease” provides a classification of the progres- sion of VHD with 4 stages, A through D (Table 7.1). Timing of inter- vention for most VHD is guided by the onset of symptoms, severity of VHD, and evidence of adverse cardiac remodeling. Therefore, a thorough history and physical examination along with a comprehen- sive transthoracic echocardiogram (TTE) are essential in the evalua- tion of patients with known or suspected VHD. Other cardiac testing modalities can help to determine the severity of VHD and the pres- ence of symptoms. Once intervention is contemplated, each individual patient’s surgical risk should be assessed. If surgical risk is high or pro- hibitive, transcatheter approaches may be an option.