Abstract
Systolic anterior motion of the anterior mitral leaflet and asymmetric septal hypertrophy (ASH) are characteristic features of hypertrophic obstructive cardiomyopathy (HOCM) on an echocardiogram. Among 9, 670 patients over 60 years old examined by echocardiography from January, 1984 to October, 1990, 55 patients showed systolic anterior motion of the anterior mitral leaflet and/or the chordae tendinae (SAM). We investigated clinical features and morphological features of the left ventricle on an echocardiogram in the 55 patients with SAM. They were classified into three groups according to the degree of SAM. Thirty eight cases (group I) had no mitral and/or chordal-septal contact, 10 (group II) had brief contact (<30% on the echocardiographic systole) and 7 (group III) had prolonged contact (≥30%). Ages ranged from 60 to 99 with a mean age of 78.2 years. There were 19 males and 36 females and there was a predominance of females in each group. Thirty five cases had hypertension and 34 left ventricular hypertrophy on electrocardiograms. One case of group I, 3 of group II and 7 of group III had a clinical diagnosis of HOCM. In comparison with each group, the incidence of LVH (SV1+RV5≥35mm) was 52% in group I, 90% in group II and 83% in group III and that of LVH (SV1+RV5≥70mm) was 29%, 20% and 67%, respectively. On echocardiographic examination, the diastolic descent rate of the anterior mitral leaflet in the 3 groups was 36.1±13.1mm/sec, 19.4±13.1mm/sec and 10.7±11.8mm/sec (p<0.01). The septal thickness was 14.4±4.3mm, 13.9±3.3mm and 18.2±4.1mm and the posterior wall thickness was 11.6±2.2mm, 12.2 ±3.6mm and 13.6±4.8mm. In particular, septal hypertropy led to ASH in group III. The left ventricular end-diastolic dimension was 42.7±8.5mm, 36.6±2.9mm and 38.9±5.6mm in each group. The IVS-AML distance at the onset of systole was 16.7±4.5mm, 13.4 ±3.2mm and 12.4±3.9mm, respectively (p<0.05). The incidence of proximal septal bulge was 32%, 70% and 86% (p<0.01). Out of 9 autopsied cases (6 in group I, 1 in group II2 in group III), 3 of group II and III demonstrated the septal band characteristic of HOCM in the elderly. The characteristic features of 55 aged patients with SAM were as follows; 1) small left ventricular cavity on the low side of the normal range, 2) slackened chordae due to the small left ventricular cavity, 3) narrowing of the left ventricular outflow tract due to the narrow aortoseptal angle and the proximal septal bulge, 4) anterior displacement of the mitral valve due to the mitral ring calcification, 5) good contraction of the left ventricle. This study showed that some of the abovementioned factors, in combinaiton, might cause SAM and the progression of SAM was associated with increased narrowing of the left ventricular outflow tract and the progressive hypertrophy of the septum. The septal band was observed in cases of Group II and III, which had mitral and chordal-septal contact on systole.
