Comparison of dobutamine stress echocardiography and exercise echocardiography in evaluating left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy

Objective: To compare left ventricular outflow tract (LVOT) gradient induced by dobutamine stress echocardiography (DSE) and exercise echocardiography (EE) in patients with hypertrophic cardiomyopathy (HCM).

Methods: DSE and EE were performed in 40 consecutive patients with HCM and LVOT gradient < 50 mm Hg (1 mm Hg = 0.133 kPa) at rest. Dobutamine was administered intravenously at incremental doses of 200, 400, 600, 800 and 1200 µg/min at 5 min intervals. LVOT gradients were measured at rest, at peak exercise and during each dose of DSE.

Results: LVOT gradient at rest was lower than 30 mm Hg in 36 patients and between 30 and 49 mm Hg in 4 patients. Of the 36 patients with LVOT gradient < 30 mm Hg at rest, mechanical LVOT obstruction (latent LVOTO) was evidenced in 17 patients during EE and in 18 patients during DSE and good consistency (91.7%, kappa value 0.833) was found between the two maneuvers. The provoked gradient was similar between DSE at 800 µg/min and EE at peak exercise (P = 0.181). In the 4 patients with LVOT gradient between 30 and 49 mm Hg [(38.8 ± 2.6) mm Hg], LVOT gradient increased to (85.3 ± 26.4) mm Hg during EE and (105.0 ± 28.0) mm Hg during DES.

Conclusions: DES and EE are comparable and suitable provoke methods for identifying LVOT obstruction in patients with HCM.