Significance of systolic anterior motion of the mitral valve during dobutamine stress echocardiography

Left ventricular outflow tract obstruction related to systolic anterior motion of the mitral valve (SAM) induced during dobutamine stress echocardiography (DSE) is not unusual but its significance is not established. A total of 100 consecutive patients (mean age 62 ± 12 years; 67% male) without previous transmural myocardial infarction, valvular disease, or hypertrophic cardiomyopathy, undergoing DSE to assess the presence of myocardial ischemia, were prospectively evaluated. A SAM with DSE was searched and correlated with clinical and baseline echocardiographic findings. Patients who demonstrated SAM with DSE were selected for exercise echocardiographic Doppler study with bicycle, within 6 months of the DSE. The development of an intraventricular gradient with DSE or exercise was defined as a new gradient of ≥36 mm Hg. In all, 23 patients developed SAM during DSE with a mean gradient of 79 ± 33 mm Hg (range: 39-144 mm Hg) and mitral regurgitation related to SAM. Compared with patients without SAM, patients who developed SAM with DSE were characterized at rest by a smaller mitroaortic angle and septoaortic angle, a higher posterior mitral leaflet length, and a smaller left ventricular cavity. Neither ischemic nor hypotensive response during DSE were correlated to SAM. In the group of patients with SAM, of the 9 patients who were referred for unexplained chest pain or dyspnea, 5 reproduced symptoms with DSE, compared with 2 of 17 patients in the group without SAM (P = .005). Despite these findings, only 3 of the 16 patients who underwent exercise echocardiography Doppler study developed SAM (two with symptoms), with a wide range of achieved heart rate, compared with DSE. Although patients with SAM with DSE exhibit predisposing echocardiographic findings, the clinical impact of this phenomenon is real in only a minority of patients, particularly those who experienced unexplained dyspnea or chest pain.