Regional left ventricular contractile dynamics in hypertrophic cardiomyopathy evaluated by magnetic resonance imaging.

To assess regional myocardial function in hypertrophic cardiomyopathy (HCM), we examined systolic wall thickening (%WT) and percent change of segmental wall area (%AR) by cine magnetic resonance imaging. We studied 23 normal volunteers without evidence of heart disease (group 1) and 40 patients with HCM (group 2). Short-axis images of the left ventricle were recorded at the base and the apex, and were divided into five segments. There were no significant differences in %WT and %AR among the segments in group 1, while %WT and %AR at the apex were higher than values for corresponding segments at the base. The patients with HCM (group 2) were classified into three groups according to end-diastolic wall thickness: group 2a, less than 12 mm; group 2b, 12-15 mm and group 2c, greater than 15 mm. Both the %WT and %AR at the base were significantly higher in group 2a than in the other groups, but were significantly lower in group 2c than in group 1 or group 2a (%WT and %AR in groups 1, 2a, 2b, and 2c respectively: 51 +/- 29 and 19 +/- 17; 83 +/- 40 and 34 +/- 18; 47 +/- 38 and 16 +/- 14; and 32 +/- 21 and 9 +/- 8). Both %WT (40 +/- 24) and %AR (14 +/- 12) at the apex were significantly lower in group 2c than in the other groups (87 +/- 45 and 38 +/- 31 in group 1; 89 +/- 41 and 39 +/- 31 in group 2a; and 61 +/- 27 and 24 +/- 15 in group 2b). Myocardial shortening in the normal volunteers was greater at the apex than at the base. In patients with HCM, regional myocardial function was decreased in association with the degree of hypertrophy, with the wall function of the normal segments appearing to be increased in a possible compensatory mechanism.