Cine magnetic resonance imaging was used to analyze global and regional left ventricular function in seven patients with obstructive hypertrophic cardiomyopathy (HC) and 10 normal subjects. In patients with HC a 38% higher left ventricular mass index (106.4 +/- 20.2 gm/m2 vs 77.0 +/- 16.1 gm/m2, p < 0.005) associated with a lower end-diastolic volume index (44.9 +/- 8.9 ml/m2 vs 58.3 +/- 9.0 ml/m2, p < 0.005) resulted in an 85% higher mass-to-volume ratio (2.4 +/- 0.52 vs 1.3 +/- 0.57, p < 0.0005). Stroke volume did not differ significantly, whereas ejection fraction was higher (80.4% +/- 6.5% vs 65.4% +/- 7.2%, p < 0.0005) in patients with HC. Although early diastolic filling fraction was smaller in patients with HC (61.0% +/- 22.8% vs 68.4% +/- 14.6%), the difference did not reach significance because of substantial variability. In patients with HC (in contrast to normal subjects) the time to maximal wall thickening was shorter (p < 0.025) in the hypertrophied basal region of the ventricle (223 +/- 42 msec) than in the apical region (267 +/- 35 msec), reflecting asynchrony between these regions. Additionally, in patients with HC the standard deviation of the time to maximal wall thickening in the basal region was significantly higher when compared with that of normal subjects (40.0 +/- 24 msec vs 16.9 +/- 17 msec, p < 0.0005), reflecting asynchrony even within one region. Thus magnetic resonance imaging can detect regional left ventricular asynchrony, an important cause of impaired diastolic function, in patients with HC and normal global systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)