Pathophysiology of Congenital Heart Disease in the Adult, Part II

Abstract

With the successes in cardiothoracic surgery over the past 3 decades, adults with congenital heart disease (CHD) outnumber, for the first time, their pediatric counterparts.1,2 As a result, adult patients with CHD are beginning to appear more frequently in the practices of adult cardiologists. This series is designed to provide a review of the pathophysiology and natural history of common congenital heart problems that are now being seen by adult cardiologists. In the first part, simple shunt lesions were reviewed. This section will examine the physiology and natural history of some of the more common congenital obstructive lesions that may be seen by adult cardiologists, as well as indications for intervention. Principally, these lesions will include ventricular outflow obstructions that may or may not have undergone prior intervention. Congenital obstructions of systemic and pulmonary venous return, congenital intra-atrial obstructions, and congenital atrioventricular valve stenosis will not be included in this review because they are far less common and present clinically predominantly in childhood. In the normal circulation, the ventricular outflow tracts, semilunar valves, and great arteries present no obstruction to flow. Congenital narrowing of any of these pathways increases ventricular afterload and in more distal lesions causes maldistribution of flow (see individual defects below). In response to the increased afterload, physiological ventricular hypertrophy occurs, which results in thicker chamber walls, reduced chamber compliance, and higher filling pressures in the atrium. With severe noncompliance (diastolic dysfunction) venous congestion may occur, with exertion or even at rest, which limits cardiac output and physical activity in this population. A reduced stroke volume may also be a direct consequence of increased afterload and may be particularly important in the face of increased demands. All patients with hemodynamically significant obstructions of large ventriculoarterial pathways will present with a heart murmur, the result of the …