Quantifying diastolic function in hypertrophic cardiomyopathy: the ongoing search for the holy grail.

Hypertrophic cardiomyopathy (HCM) is a primary autosomal-dominant disorder of the myocardium caused by mutations in sarcomeric contractile proteins. Histopathologically, it is associated with myocardial hypertrophy, fiber disarray, increased loose connective tissue, and fibrosis, which are all thought to interfere with myocardial force generation and relaxation.1–3 There is tremendous heterogeneity in the phenotypic expression of HCM, which is generally unrelated to genotype. This is shown by the variability of the age of onset of clinical disease, degree and location of hypertrophy, and presence and site of intraventricular dynamic pressure gradients. Despite this heterogeneity, almost all patients with HCM have some degree of diastolic dysfunction. The presence of subtle changes in LV filling may even identify patients with preclinical disease without LV hypertrophy. Interventions such as medical therapy, septal alcohol ablation, and surgical myectomy improve symptoms by both reducing the left ventricular (LV) outflow tract gradients and improving diastolic function.