ESSENTIALS OF DIAGNOSIS
May present with dyspnea, chest pain, syncope.
Though LV outflow gradient is classic, symptoms are primarily related to diastolic dysfunction.
Echocardiogram is diagnostic. Any area of LV wall thickness greater than 1.5 cm defines the disease.
Increased risk of sudden death.
Hypertrophic cardiomyopathy is noted when there is LVH unrelated to any pressure or volume overload. The definition has evolved over time; while it traditionally has been defined by LV outflow obstruction due to septal hypertrophy, now it is considered present any time that any LV wall is measured at more than 1.5 cm thick on an echocardiogram. This allows for many forms to be considered that do not create LV outflow obstruction. The increased wall thickness reduces LV systolic stress, increases the EF, and can result in an “empty ventricle” at end-systole. The interventricular septum may be disproportionately involved (asymmetric septal hypertrophy), but in some cases the hypertrophy is localized to the mid-ventricle or to the apex. The LV outflow tract is usually narrowed during systole due to the hypertrophied septum and systolic anterior motion of the mitral valve occurs as the anterior mitral valve leaflet is pulled into the LV outflow. The obstruction is worsened by factors that increase myocardial contractility (sympathetic stimulation, digoxin, and postextrasystolic beat) or that decrease LV filling (Valsalva maneuver, peripheral vasodilators). The amount of obstruction is preload and afterload dependent and can vary from day to day. The consequence of the hypertrophy is elevated LV diastolic pressures rather than systolic dysfunction. Rarely, systolic dysfunction develops late in the disease. The LV is usually more involved than the RV, and the atria are frequently significantly enlarged.
Hypertrophic cardiomyopathy is inherited as an autosomal-dominant trait with variable penetrance and is caused by mutations of one of a large number of genes, most of which code for myosin heavy chains or proteins regulating calcium handling. The prognosis is related to the specific gene mutation. Patients usually present in early adulthood. Elite athletes may demonstrate considerable hypertrophy that can be confused with hypertrophic cardiomyopathy, but generally diastolic dysfunction is not present in the athlete and this finding helps separate pathologic disease from athletic hypertrophy. The apical variety is particularly common in those of Asian descent. A hypertrophic cardiomyopathy in older adults (usually in association with hypertension) has also been defined as a distinct entity (often a sigmoid interventricular septum is noted with a knob of cardiac muscle below the aortic valve). Mitral annular calcification is often present. Mitral regurgitation is variable and often dynamic, depending on the degree of outflow tract obstruction.
The most frequent symptoms are dyspnea and chest pain (see Table 10–17). Syncope is also common and is typically postexertional, when diastolic filling diminishes due to fluid loss and tachycardia increasing LV ...