Does Hypertrophic Cardiomyopathy Change into Dilated Cardiomyopathy-Like Features?

Hypertrophic cardiomyopathy sometimes progresses to dilated cardiomyopathy-like features [1–5]. The etiology of the progression remains to be determined. Recently, we reported a patient with hypertrophic cardiomyopathy who showed a persistent elevation of serum creatine kinase (CK)-MB and lactate dehydrogenase 1 (LDH1) activities for several years and developed dilated cardiomyopathy-like features [6]. Thus, the persistent elevation of cardiac enzymes might be closely related to the progression from a typical hypertrophic cardiomyopathy to a dilated left ventricle in the patient. To elucidate the prognosis of hypertrophic cardiomyopathy it is very important to know whether the cardiac enzymes elevation occurs usually in patients with hypertrophic cardiomyopathy or only in the specific type. The total CK activity of myocardial origin is composed of three different components, CK-MM, CK-MB and a lesser amount of CK-BB. CK-MM itself is also composed of three main isoforms, MMa, MMb and MMc. CK activity in the myocardium is primarily MMa, and in acute myocardial infarction a rapid and transient rise in MMa activity in the serum is observed. The serum MMa/MMc activity ratio is useful to estimate the process of myocardial injury due to myocardial infarction [7,8]. We recently reported that the measurement of MMa/MMc ratio was also useful to estimate the myocardial condition in patients with hypertrophic cardiomyopathy [9].