Adult Congenital Heart Disease



Adult Congenital Heart Disease


Benjamin S. Hendrickson

Marc V. Lee

Jennifer DeSalvo

Elisa A. Bradley



INTRODUCTION

Surgical and medical advances have touched fewer fields more profoundly than congenital heart disease (CHD). As a result, there are now more adults surviving with CHD (ACHD) than there are children.1 Current data suggest that approximately 4 to 10 in every 1000 live births in the United States is affected by CHD, and that the number surviving into and throughout adulthood will continue to rise.2,3,4,5,6 Given the increased size of the adult population with CHD, there has been increased focus in how to best care for these patients. This has resulted in the establishment and development of a subspecialty field within cardiology dedicated to the care of ACHD patients. As recent as the past decade, there has been evidence that supports that this specialized ACHD care has led to improved survival.7 However, the field is complex in that there is significant heterogeneity in the spectrum of CHD diagnoses and treatment options available. Therefore, the goal here is to provide a general overview of the types of CHD that can be seen in the adult population, clinical presentation, management, and discussion of ongoing lifelong care.


PATHOGENESIS

CHD arises from abnormal cardiovascular development during embryogenesis or in the transition to postnatal circulation. Therefore, an understanding of cardiac morphogenesis is necessary to understand the anatomic and pathophysiologic consequences of individual defects and corrective or palliative treatment options.

Cardiac morphogenesis begins during the third week of embryogenesis with the formation of the primitive heart tube. It develops from paired clusters of mesodermal cells that proliferate longitudinally, canalize, and fuse in the ventral midline to form a single heart tube (Figure 17.1A,B).8 This consists of an inner endocardium, gelatinous connective tissue, and outer myocardium. The heart tube also conducts action potentials, resulting in cardiac contraction during the third week. As it elongates during the fourth week, primitive chambers develop and looping occurs to establish polarity. This leads to the sinus venosus, connected to the venous system caudally, and primitive atrium, to move above and behind the primitive ventricle (Figure 17.1B). The bulbus cordis and truncus arteriosus, on the other hand, are connected to the aortic arches cranially.8 Septation of the chambers occurs between 4 and 6 weeks (Figure 17.1C,D). The ventricular outflow tracts derive from migration of neural crest cells that proliferate within the bulbus cordis and truncus arteriosus to form ridges, which fuse and spiral to form an aorticopulmonary septum divided into the pulmonary artery and aorta, respectively (Figure 17.1E). The aortic and pulmonic valves are derived from endocardial cushions of the ventricular outflow tracts, whereas mitral and tricuspid valves are derived from that of the atrioventricular canal. Throughout cardiac morphogenesis, fetal circulation allows for oxygenated blood from the placenta to be shunted from the umbilical vein to the inferior vena cava via the ductus venosus bypassing hepatic circulation, from the right to left atria via the foramen ovale, and from the pulmonary artery to the aorta to the systemic circulation via the ductus arteriosus bypassing the lungs. The anatomic and physiologic transition to postnatal circulation after delivery lead to shunt closure, as pulmonary vascular resistance decreases.

CHD is felt to arise from the interaction of multiple complex factors, and approximately only 15% has been linked to inherited or de novo genetic mutations. Environmental and maternal factors are also important, and risk factors for CHD in the offspring include: maternal chronic or gestational diseases, maternal medical illness, exposure to teratogenic medications or toxins in utero, and exposure to various environmental factors.9 As a child with CHD progresses into adulthood, the development of sequelae from their native CHD or surgical intervention, in addition to acquired comorbidities, including hypertension, hyperlipidemia, obesity, and coronary disease, may exacerbate the physiologic regulatory mechanisms of CHD, ultimately affecting overall health and quality of life.9

The AHA/ACC have proposed comprehensive guidelines that highlight both the anatomic abnormalities and physiologic consequences of CHD.10 This classification system is used to help define appropriate evaluation, management, and follow-up care in the disparate ACHD population. The anatomic portion of classification is divided into the complexity of CHD: simple, moderate, and severely complex. The physiologic stage encompasses hemodynamic and anatomic sequelae, which vary from valvular involvement, pulmonary vascular disease, ventricular
dysfunction, and arrhythmia, among others. A diagrammatic representation of the Anatomic/Physiologic ACHD Classification system is represented in Algorithm 17.1.







CLINICAL PRESENTATION

It is important to understand that the heterogenous nature of CHD impacts the clinical presentation of this population. In general, the clinical presentation may be affected by the type, number, or magnitude of the underlying defect and repair. Some examples of common congenital defects/patterns and consequences are outlined in Table 17.1.

The most anatomically severe or hemodynamically significant derangements generally present soon after birth with cyanosis, heart failure, or cardiovascular collapse and require percutaneous or surgical intervention to remain compatible with life. Initial stabilization may require prostaglandin E to maintain patency of the fetal ductus arteriosus to provide pulmonary blood flow. Critical cardiac lesions palliated by early surgery include: transposition of the great arteries (TGA), aortic coarctation (CoA), hypoplastic ventricles, and obstructed total anomalous pulmonary venous connections (TAPVCs). Modern transcatheter approaches with balloon valvuloplasty can delay or eliminate neonatal surgery for many conditions.

Less severe or small defects may present in adolescent or adulthood without obvious symptoms. Physiologic adaptation to the progressive effects of smaller shunts or slow valve deterioration may go unnoticed until hemodynamic compromise occurs. Patients may present with fatigue, mild exertional complaints, or a new murmur. There are several examples of CHD that may present later in life. For instance, atrial septal defects (ASDs) and partial anomalous pulmonary venous connections (PAPVCs) can evade detection for years and are forms of CHD frequently diagnosed in adulthood. Common auscultatory findings with pre-tricuspid valve shunts, such as an ASD, are wide splitting of the second heart sound and a murmur of pulmonary stenosis, because of the increased flow across the pulmonary valve. Another example of late CHD presentation may include Ebstein anomaly of the tricuspid valve, which is associated with accessory pathways, and may present for evaluation of an abnormal electrocardiogram. Yet another example is the bicuspid aortic valve, which is one of the most common congenital malformations yet if normal function is present and may go undetected. Severe cardiac disease arising from undiagnosed CHD in adulthood is less common, but when present often is a result of inattention to symptoms, avoidance of medical care, or lack of access to health care.















Adults with previously palliated CHD represent another group that may present late to care. Many patients report feeling well or have the impression they were “fixed” and therefore did not seek follow-up. Unfortunately, CHD specialists discover hemodynamically significant lesions in approximately 60% of patients with CHD who have been lost to follow-up. In this group, there is a threefold increase in the need for late intervention/surgery.11


May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Adult Congenital Heart Disease
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