[Mode of splitting of the second heart sound in patients with hypertrophic cardiomyopathy].

Mode of the splitting of the second heart sound ( IIs ) and left ventricular systolic time intervals (STIs) in patients (pts) with hypertrophic cardiomyopathy were compared with those in hypertension (HT) with the global hypertrophy of the left ventricular wall. Forty-seven pts with hypertrophic cardiomyopathy [non-obstructive type (HCM, 30 pts), obstructive type (HOCM, 17 pts)] and 21 pts with HT were studied. The pts with HCM were classified as septal hypertrophic type (19 pts) and apical hypertrophic type (11 pts) on the basis of the echocardiographic findings. The pts with HOCM were classified as resting type (13 pts) and latent type (provoked by amyl nitrite: 4 pts) on the basis of the obstructive sign at rest. Mode of the splitting of the IIs : a) The pts with HCM showed a wide splitting of the IIs . The mean split interval during held expiration (IIA-IIP) was 41.0 +/- 9.9 msec. Twenty pts (67%) showed abnormal respiratory splitting. The mean IIA-IIP interval in septal hypertrophic type (45.3 +/- 9.0 msec) was significantly wider than that in apical hypertrophic type (33.6 +/- 6.7 msec) (p less than 0.05). There was a positive correlation between IIA-IIP interval and the thickness of the upper portion of the interventricular septum (r = 0.63). b) Nine out of 13 pts with resting type of HOCM showed a paradoxical (reversed) splitting with a mean IIA-IIP interval of -23.8 +/- 24.4 msec. On the other hand, pts with latent type showed a wide splitting similar to HCM with a mean IIA-IIP interval of 35.0 +/- 7.1 msec. c) The pts with HT showed a single IIs or physiological splitting. The mean IIA-IIP interval was 14.5 +/- 9.3 msec, which was significantly decreased than that of normals or the pts with HCM (p less than 0.01). Left ventricular systolic time intervals: a) The pts with an either type of HCM showed a short corrected left ventricular electromechanical systole [(Q-IIA)c] due to the shortening of the corrected left ventricular ejection time (LVETc). b) The pts with resting type of HOCM showed a long (Q-IIA)c due to the prolongation of LVETc, but latent type showed the same change as in HCM. c) The pts with HT showed a tendency of prolongation of (Q-IIA)c due to slightly short LVETc and long corrected pre-ejection period (PEPc). Fractional shortening of the left ventricle (%FS) and mean velocity of circumferential fiber shortening (mean VCF) calculated from echocardiograms were significantly greater in both types of HCM than those in normals and HT (p less than 0.05). Left ventricular end-diastolic dimension was significantly decreased in the pts with septal hypertrophic type of HCM than in others.(ABSTRACT TRUNCATED AT 400 WORDS)