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 > or =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.