Left ventricular hypertrophy and morphology in familial hypertrophic cardiomyopathy associated with mutations of the beta-myosin heavy chain gene.

OBJECTIVES The purpose of this study was to determine the spectrum of left ventricular hypertrophy and ventricular morphology in adults with hypertrophic cardiomyopathy due to mutations of the beta-myosin heavy-chain gene. BACKGROUND Although echocardiography is an important test in diagnosing hypertrophic cardiomyopathy, the lack of an independent diagnostic criterion has been an obstacle in determining the full echocardiographic spectrum of this disease. Mutations in the beta-myosin heavy chain gene occur in approximately 50% of familial cases; in members of families with a known mutation, the diagnosis can be made with certainty. METHODS Echocardiograms from 39 genetically affected and 30 genetically unaffected adult family members over age 16 years from 10 families were analyzed. Left ventricular wall thickness was measured at 10 separate locations, and the presence of systolic anterior motion of the mitral valve, right ventricular hypertrophy and left ventricular morphology was evaluated independently by three separate observers without knowledge of the genetic diagnosis. RESULTS The mean maximal wall thickness in the genetically affected group was 24 +/- 8 mm (range 11 to 40), compared with 11 +/- 2 mm (range 7 to 16) in the unaffected group (p < 0.0001). Systolic anterior motion of the mitral valve or chordae tendineae with or without leaflet-septal contact was present in 62% of the affected group and in none of the unaffected group. The morphologic finding of reversed septal curvature was present in 79% of the affected group and in none of the unaffected group. Seventy-seven percent of patients in the affected group had a septal/free wall ratio > or = 1.3 compared with 6% in the unaffected group, with a septal/posterior wall ratio > or = 1.3 associated with only a 55% probability of being affected. CONCLUSIONS The two-dimensional echocardiographic spectrum of hypertrophic cardiomyopathy in a genetically defined adult population is broad. Previous echocardiographic criteria may be too strict to diagnose the disease in some patients who are genetically affected and therefore at risk for adverse events related to the disease. Ultimately, genetic testing may supersede echocardiography in diagnosing hypertrophic cardiomyopathy.