idiopathic hypertrophy of the myocardium resulting in
left ventricular hypertrophy (LVH) which is usually assymetric involving the interventricular septum in 2/3rds of cases
25% have obstructed outflow at rest, while 70% have obstructed outflow under certain conditions (“dynamic outflow obstruction”)
30% have abnormal vascular responses and inability to increase systolic blood pressure during exercise
one of the commonest causes of sudden death in young athletes and is often asymptomatic prior
arrhythmias are common especially atrial fibrillation and supraventricular tachycardias.
50-60% are due to a mutation in one of 9 sarcomeric genes, usually inherited as autosomal dominant or arise de novo
45% of these mutations occur in the β myosin heavy chain gene on chromosome 14 q11.2-3
35% involve the cardiac myosin binding protein C gene
an insertion/deletion polymorphism in the gene encoding for angiotensin converting enzyme (ACE) alters the clinical phenotype of the disease
troponin T mutations are particularly dangerous and are associated with a 50% mortality before the age of 40
prevalence is 0.2% - 0.5% of the general population
a non-obstructive variant of HCM is apical hypertrophic cardiomyopathy, also called Yamaguchi Syndrome or Yamaguchi Hypertrophy, first described in individuals of Japanese descent