Systolic Anterior Motion of the Mitral Valve in the Absence of Asymmetric Septal Hypertrophy

MINTZ, GARY S. M.D.
KOTLER, MORRIS N. M.D.
SEGAL, BERNARD L. M.D.
PARRY, WAYNE R.

William Likoff Cardiovascular Institute, Hahnemann Medical College and Hospital, Philadelphia, Pennsylvania.

Address for reprints: Morris N. Kotler, M.D., William Likoff Cardiovascular Institute, Hahnemann Medical College and Hospital, 230 North Broad Street, Philadelphia, Pennsylvania 19102.

Received February 9, 1977; revision accepted August 25, 1977.

Circulation 57(2):p 256-263, February 1978.

SUMMARY

Asymmetric septal hypertrophy (ASH) is considered thi unifying link in the spectrum of hypertrophic cardiomyopathies. ASH and mitral valve systolic anterior motion (SAM) are the two most important echocardiographic criteria for the diagnosis of idiopathic hypertrophic subaortic stenosis (IHSS). Ten patients found to have SAM without ASH were studied. Septal thickness, thickening, and excursion were normal.

Seven patients had left ventricular ejection times (LVET) measured before and after amyl nitrite inhalation. In six of them, corrected LVET increased by more than 40 msec. Four patients underwent diagnostic cardiac catheterization. Resting or provocable left ventricular outflow tract (LVOT) gradients were demonstrable in all four patients.

The echocardiographic features in patients with SAM alone, ASH and SAM, and ASH alone were compared. LVOT measurements in patients with SAM alone (2.2 ± .4 cm) and ASH and SAM (2.1 ± .5 cm) were similar and narrower than in patients with ASH alone (2.8 ± .5 cm, P < 0.001). Ejection fractions in patients with SAM alone (79 ± 10%) were greater than in patients with ASH and SAM (66 ± 16%, P < 0.02) or ASH alone (60 ± 15%, P < 0.001). Thus, dynamic left ventricular outflow obstruction can exist in the absence of echocardiographic ASH. LVOT width and abnormal LV ejection dynamics may contribute to the LVOT obstruction with or without the presence of ASH.