Applying HF Guidelines to Adult Congenital Heart Disease Patients
At the current time, there is a very small evidence base from which to draw recommendations for the treatment of heart failure in adults with CHD. As stated previously, there is a strong evidence base for the treatment of adults with heart failure, but it is unlikely that there were significant numbers of patients in any of these trials who had repaired or unrepaired CHD. For those adult patients with CHD and a systemic left ventricle and ischemic coronary artery disease or a cardiomyopathy, it is probably reasonable to extrapolate from adult heart failure trials that have enrolled patients with coronary artery disease. However, this represents few of the adults with CHD. As described previously, the substrate for heart failure in these patients is quite unique. Many of these patients will have systemic left ventricles, and some have developed heart failure due to left ventricular systolic dysfunction. In these patients, it may be reasonable to extrapolate some of the treatment rationale from adult and, to a lesser extent, pediatric heart failure trials. In those with more complex anatomy, for example a systemic ventricle that is not a left ventricle, the rationale for applying adult heart failure treatment guidelines is much less clear. Each of the four stages of the ACC/AHA guidelines for heart failure will be reviewed in terms of their treatment application to adults with CHD.

As adults with CHD age, they will be at risk for the same risk factors for heart failure that all adults are at risk for: hypertension, atherosclerotic heart disease, diabetes, obesity and the metabolic syndrome. A much smaller percentage of these patients will be exposed to cardiotoxins, such as anthracyclines. Adults with CHD should be screened and monitored for all of these risk factors and should be treated for these conditions if they are discovered. Subgroups of adults with CHD are at increased risk of myocardial ischemia or infarction due to coronary abnormalities and obstructive lesions of the left ventricle and aorta. Abnormal origins of the coronary arteries (e.g., left coronary arising from the right sinus of Valsalva and coursing between the aorta and pulmonary artery) can predispose to sudden death, ischemia, infarction and accelerated atherosclerosis. Certain surgical treatments of CHD such as the arterial switch operation for transposition of the great arteries or the Ross operation for aortic stenosis require manipulation and/or relocation of the coronary arteries. This puts patients at risk for ostial stenosis, in addition to coronary artery kinking, stretching and narrowing. In addition, there is increasing evidence that the resultant denervation of the proximal coronary arteries from this type of surgical manipulation may cause long-term abnormalities in coronary artery growth, vascular reserve and function. Since survivors of these surgeries are relatively young at the current time, long-term follow-up will be necessary to learn the clinical consequences of these interventions. In patients with left ventricular obstruction distal to the coronary artery orifices (e.g., supravalvar aortic stenosis and coarctation of the aorta), some degree of hypertension is common at rest or with exercise even after successful surgical or transcatheter repair. The coronary arteries in supravalvar aortic stenosis are often abnormal at their origins and, at times, even more distally. It has long been known that even in children with valvar aortic stenosis, there is potential for a life-long coronary supply/demand mismatch that increases their risk of heart failure. Finally, adults with CHD may have a higher incidence of certain cardiovascular risk factors than healthy age-matched controls.

Structural heart disease without signs or symptoms of heart failure is a common if not universal finding in adults with CHD. In those who have ‘repaired’ CHD, the resting hemodynamics can be normal or abnormal. Even in those who have normal hemodynamics, many of these patients have had either a thoracotomy or sternotomy with subsequent cardiotomy or at least arteriotomy (e.g., coarctation of the aorta). Some of these repaired lesions with normal hemodynamics may be at risk for long-term abnormalities. As stated previously, patients with transposition of the great arteries after the arterial switch operation may be at risk for abnormalities of the coronary arteries. A large percentage of these repaired adults with CHD will have residual valve disease that will require close monitoring and possibly medical, transcatheter or surgical intervention. Reduced systolic and/or diastolic ventricular function is a common finding in repaired and unrepaired CHD, and is often difficult to quantitate, both before and after the development of symptoms. Treatment options for these patients include medical, transcatheter and surgical interventions. There are no good data to guide medical treatment of these patients with asymptomatic ventricular dysfunction. The current ACC/AHA guidelines recommend treatment of patients with asymptomatic LV systolic dysfunction with ACE inhibitors (or angiotensin receptor blockers [ARBs] if intolerant to ACE inhibitors) and possibly β-blockers. In adults with CHD with a systemic left ventricle, if one assumes that the underlying substrate is similar to adults with dilated cardiomyopathy or ischemic heart disease, ACE inhibitors, ARBs and/or β-blockers may be of benefit in preventing or delaying the onset of symptomatic heart failure. The optimal management of asymptomatic ventricular dysfunction in those patients with a systemic ventricle that is not a left ventricle (e.g., dTGA status post atrial switch, congenitally corrected transposition of the great arteries, single ventricle) is unknown. Although frequently used, there is no evidence that medications prevent or delay the onset of heart failure symptoms in these patients. Surgical management is the treatment of choice for asymptomatic severe valve regurgitation.

Perhaps the most challenging stage of treatment of adults with CHD is the stable, symptomatic stage. There is a large evidence base with many treatment options available to healthcare providers caring for adults with heart failure with either ischemic or nonischemic heart failure due to left ventricular systolic dysfunction. These include diuretics, digoxin, aldosterone antagonists, ACE inhibitors, ARBs and β-blockers. Unfortunately, there have not yet been any medications that have convincingly shown an improvement in symptoms or survival in adults with CHD, including ACE inhibitors or ARBs. There is ample evidence that systemic ventricles that are not left ventricles act differently at rest and respond differently to stress than left ventricles. Three recent small uncontrolled series have reported a possible benefit of β-blockers in adults with CHD and systemic right ventricular dysfunction. However, without larger trials with appropriate end points, it is not possible at the current time to know how beneficial any of these medications are in this group of patients. The indications for cardiac resynchronization therapy (CRT) and/or implantable cardioverter/defibrillator (ICDs) in this group of patients are also unclear. There are no data available for these interventions in adults with CHD, so, again, one has to extrapolate from clinical trials in adults with ischemic or dilated cardiomyopathy. In those with a systemic left ventricle, prolonged QRS of 120 ms or higher, on maximal pharmacologic therapy and NYHA Class 3–4 symptoms, CRT may be beneficial in improving symptoms, cardiac function and survival. In adults with CHD, ICDs can be life-saving. Identifying the appropriate patients for this therapy is challenging. In those with an aborted sudden death episode (secondary prevention) or malignant arrhythmias thought to be unresponsive to medical therapy, an ICD may be considered. However, the use of primary prevention is much less clear in this group of patients. The current recommendations are for patients with ischemic or nonischemic cardiomyopathy who have an ejection fraction of 30% or less with NYHA Class II–III symptoms while undergoing chronic optimal medical therapy and have a reasonable expectation of survival with good functional status for at least 1 year. In ACHD patients, there may be a greater incidence of inappropriate shocks than in other adult patients.

Treatment recommendations in this stage of heart failure have a smaller evidence base than any of the other stages. Thus, there is very little guidance available to those caring for adults with CHD and end-stage or decompensated heart failure. Within the constraints of inotropic therapy, it seems reasonable to utilize inotropes as recommended for other patients in this situation. The use of mechanical circulatory support may be much more difficult in this group of patients due to complex anatomy and repeat sternotomies. Although heart transplantation is an option for those refractory to other interventions, underlying anatomic and hemodynamic abnormalities and previous surgeries (often multiple) compound the complexity of this intervention. In the presence of severe, nonreactive pulmonary hypertension, heart–lung transplantation may need to be considered.