Dobutamine induced dynamic left ventricular outflow tract obstruction in patients with hypertrophic nonobstructive cardiomyopathy.

Some patients with hypertrophic nonobstructive cardiomyopathy (HNCM) suffer symptoms resembling those in obstructive type despite no left ventricular outflow tract (LVOT) gradient could be detected on resting echocardiography. To investigate the value of dobutamine stress echocardiography (DSE) in determining the dynamic left ventricular (LV) obstruction of patients with HNCM. The study was conducted on 31 patients who were diagnosed HNCM on resting echocardiography and 9 healthy person as a control group. Intraventricular flow acceleration of > 3 m/sec on DSE was accepted as dynamic LVOT obstruction. Group 1 and 2 included patients without and with dynamic LVOT obstruction, respectively. The occurrence of chest pain and dyspnea seen during DSE was more frequent in group 2 than group 1 and control group. The frequency of SAM was significantly higher (p < 0.05) and the septal angle was significantly lower (p < 0.001) in Group 2. The presence of SAM significantly correlated with the peak gradient (r = 0.61, p < 0.001). The septal angle had significant negative correlations with the peak gradient (r = -0.77, p < 0.001) reached at DSE. The relative risk for peak gradient was highest when septal angle was < or = 100 degrees, with a sensitivity of 93%, specificity of 80%, positive predictive value of 82%, negative predictive value of 92%, and predictive accuracy of 87%. DSE is a reliable tool for the diagnosis of dynamic LV obstruction in patients with HNCM. The presence of SAM together with a low septal angle is highly predictive for the presence of a dynamic LVOT obstruction detected by DSE.