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Hypertrophic cardiomyopathy (HCM) is a primary disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause, creating functional impairment of the cardiac muscle.〔 〕 It is a leading cause of sudden cardiac death in young athletes. The occurrence of hypertrophic cardiomyopathy is a significant cause of sudden unexpected cardiac death in any age group and as a cause of disabling cardiac symptoms. Younger people are likely to have a more severe form of hypertrophic cardiomyopathy. HCM is frequently asymptomatic until sudden cardiac death, and for this reason some suggest routinely screening certain populations for this disease.〔 A cardiomyopathy is a disease that affects the muscle of the heart. With HCM, the myocytes (cardiac contractile cells) in the heart increase in size, which results in the thickening of the heart muscle. In addition, the normal alignment of muscle cells is disrupted, a phenomenon known as ''myocardial disarray''. HCM also causes disruptions of the electrical functions of the heart. HCM is most commonly due to a mutation in one of nine sarcomeric genes that results in a mutated protein in the sarcomere, the primary component of the myocyte (the muscle cell of the heart). These are predominantly single-point missense mutations in the genes for beta-myosin heavy chain (MHC), myosin-binding protein C, cardiac troponinT, or tropomyosin. These mutations cause myofibril and myocyte structural abnormalities and possible deficiencies in force generation. While most literature so far focuses on European, American, and Japanese populations, HCM appears in all ethnic groups. The prevalence of HCM is about 0.2% to 0.5% of the general population. == Signs and symptoms == The clinical course of HCM is variable. Many patients are asymptomatic or mildly symptomatic. The symptoms of HCM include dyspnea (shortness of breath) due to stiffening and decreased blood filling of the ventricles, exertional chest pain (sometimes known as ''angina'') due to reduced or restricted blood flow to the coronary arteries, uncomfortable awareness of the heart beat (palpitations) due to the aforementioned ischemia, as well as disruption of the electrical system running through the abnormal heart muscle, lightheadedness, fatigue, fainting (called syncope) and sudden cardiac death. As mentioned, dyspnea is largely due to increased stiffness of the left ventricle, which impairs filling of the ventricles, but also leads to elevated pressure in the left ventricle and left atrium, causing back pressure and interstitial congestion in the lungs. Symptoms are not closely related to the presence or severity of an outflow tract gradient. Often, symptoms mimic those of congestive heart failure (esp. activity intolerance & dyspnea), but treatment of each is different. Beta blockers are used in both cases, but treatment with diuretics, a mainstay of CHF treatment, will exacerbate symptoms in hypertrophic obstructive cardiomyopathy by decreasing ventricular preload volume and thereby increasing outflow resistance (less blood to push aside the thickened obstructing tissue). Major risk factors for sudden death in individuals with HCM include prior history of cardiac arrest or ventricular fibrillation, spontaneous sustained ventricular tachycardia, family history of premature sudden death, unexplained syncope, LV thickness greater than or equal to 30 mm, abnormal exercise blood pressure and nonsustained ventricular tachycardia. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hypertrophic cardiomyopathy」の詳細全文を読む スポンサード リンク
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