[Dynamic left ventricular outflow tract obstruction induced by exercise]

Dynamic left intraventricular outflow tract obstruction occurs occasionally in patients without hypertrophic cardiomyopathy. We hypothesized that dynamic intraventricular obstruction might occur during effort in patients with angina or dyspnea without evident disease. The objective of this prospective study was to investigate: a) whether it appears with effort; b) its incidence, magnitude and determining factors, and c) its clinical course.

We performed baseline and stress Doppler echocardiography in 211 patients with angina, dyspnea or both with exercise. Patients with previous myocardial infarction, valvular heart disease, ventricular dysfunction or ventricular hypertrophy without hypertension were excluded. Dynamic intraventricular obstruction was defined as intracavitary flow velocity > or =2.5 m/s.

134 patients (59 women) were included: mean age was 58 (9) years; history of hypertension was present in 69.7%, dyslipidemia in 35.8% and diabetes in 24.6%. Dynamic intraventricular obstruction appeared in 18 patients (13.4%), with gradients ranging between 25 and 53 mmHg (mean 32.19 [6.6]). Demographic variables, cardiovascular risk factors and exercise performed were similar in group A (with obstruction) and group B (without obstruction). No patient in group A had evidence of ischemia. Five patients in this group had symptoms during exercise; the gradients were greater in these patients (42.65 [10.5] vs 28.15 [2.37] mmHg; P<.0001) than in the remaining group A patients. Left ventricular outflow tract size was found to be the only independent predictive factor in the multivariate analysis. After 369.9 (133.5) days of follow-up, no cardiac events were recorded.

Our study suggests that some patients with angina or dyspnea without evidence of ischemia may develop dynamic left ventricular outflow tract obstruction induced by effort.