Angiographic Demonstration of the Ventricular Septum

In the cardiac disease, idiopathic hypertrophic subaortic stenosis (IHSS) (1), there is hypertrophy of the myocardium which is often asymmetrically distributed. Although published descriptions appeared earlier, it was not until a clinical report by Brock (3) in 1957 and a pathologic report by Teare (10) in 1958 that the disease became well known. Since that time many other papers have appeared. The disease is much more common than was first realized. Most of the authors describing their cases emphasize that the often massive myocardial hypertrophy may primarily involve the ventricular septum (2, 4, 8, 10, 11), although usually the free wall of the left ventricle and sometimes the right ventricle are involved as well. Frequently the first manifestation of the disease is a heart murmur. The most common symptoms are dyspnea and angina. The patient is often asymptomatic, however. The electrocardiogram is almost always abnormal (2). At catheterization the demonstration of a pressure gradient within the left ventricle, and sometimes the right ventricle, is the most significant finding. At rest, the gradient may range from 175 mm of mercury to no gradient at all, depending on the severity of the disease. In mild forms of the disease a significant gradient may be produced or a small gradient augmented with exercise or an intravenous infusion of isoproterenol. Angiocardiography plays an important role in the diagnosis of this lesion and its differentiation from fixed subaortic obstruction. The angiocardiographic features are variable and are caused by distortion of the ventricular cavities by the abnormal muscle. The left ventricular cavity is elongate and may be very irregular (4) (Fig. 4, A). The lumen is usually narrow (7) and may be constricted in the middle, particularly in systole. The inferior margin of the left ventricle and the medial wall of the right ventricle are often indented by the bulging hypertrophied muscle. The left ventricular free wall is often thickened and the coronary arteries enlarged. The left ventricular volume is usually normal or small in contrast to other cardiac myopathies (9). Often angiocardiograms, despite considerable distortion of the ventricular cavity, show no definite area of stenosis that would account for the large pressure gradients recorded. Criley (5) has presented evidence that these gradients are generated in areas of the left ventricle completely obliterated in systole. The contractions of the ventricles are forceful, but often contrast medium is trapped in the apex and therefore is slow to clear. Diastolic filling often appears to end more abruptly than normal, suggesting that this abnormal muscle is less elastic (4). Some degree of mitral insufficiency is a common observation (2, 5). The hypertrophy of the septum may be seen as a mass indenting the medial wall of the right ventricle in the frontal plane.