Problems in diagnosis and management of hypertrophic cardiomyopathy

Abstract

In the first systemic characterization ofwhat is now known as hypertrophic cardiomyopathy, Teare reported gross asymmetric hypertrophy in 9 young adults who had died suddenly.' His report captured the essence of a disease in which cardiac hypertrophy, normally the heart's way of reducing wall tension during pressure overload, could occur inexplicably, within families as well as sporadically, and cause sudden death. In the 1960s, the diagnosis was based on a midsystolic murmur and the demonstration of a subaortic gradient at cardiac catheterization; giving rise to names such as idiopathic hypertrophic subaortic stenosis (IHSS), muscular subaortic stenosis (MSS) and hypertrophic obstructive cardiomyopathy (HOCM).2 With the advent of M-mode echocardiography in the 1970s came new diagnostic criteria. The most widely used of these was asymmetric hypertrophy of the interventricular septum, defined as a ratio of septal to posterior left ventricular wall thickness of at least 1.3. By the mid 1970s, asymmetric septal hypertrophy was considered by some to be the genetically determined, pathognomonic feature of the disease.3 M-mode echocardiography imaged the upper anterior septum usually the thickest part of the left ventricle, and the upper posterior wall usually the thinnest, and thus reemphasized the asymmetric nature of hypertrophy in the condition. The two other major echocardiographic diagnostic criteria for hypertrophic cardiomyopathy were the Mmode echocardiographic features of a left ventricular outflow tract (LVOT) gradient, systolic anterior motion of the mitral valve (SAM) and premature systolic closure of the aortic valve (Figure 1). When cross-sectional echocardiography became available in the 1980s, with its ability to image the whole heart, it became clear that apart from asymmetric septal hypertrophy, which was seen in 50 to 60% of the patients, hypertrophy could be concentric (20 to 30%),4 predominantly involve the distal left ventricle (10 to 15%), or affect single myocardial segments such as the middle or distal part of the posterior septum or lateral wall. Cross sectional echocardiography also showed that about a third of the patients with hypertrophic cardiomyopathy (HCM) had right ventricular hypertrophy (Figure 2), a feature which Teare had described in his original report. 5 The diagnostic criteria for hypertrophic cardiomyopathy have evolved over 3 decades as new techniques became available. The diagnosis now includes patients with unexplained left or right ventricular hypertrophy with or without intracavitary gradients.