Effects of postural changes on left atrial function in patients with hypertrophic cardiomyopathy

Background We assessed left atrial function in normal subjects and in patie nts with hypertrophic cardiomyopathy (HCM) by using Doppler echocardiograph y at the supine position and after sudden standing. Methods and Results Twenty-seven patients with hypertrophic obstructive car diomyopathy (HOCM), 17 patients with HCM, and 35 normal subjects were studi ed. From the transmitral Doppler flow velocities, peak early and late (E an d A) waves, E/A ratio, and time velocity integrals (Ei and Ai) were calcula ted. Left atrial active contribution (LAAC) was assessed as the ratio Ei/(E i + Al). Furthermore, isovolumetric relaxation time (IVRT) was estimated by means of Doppler echocardiography. In the supine position, the E/A ratio w as similar in the 3 groups. Conversely, LAAC was significantly higher in pa tients with HOCM (24.4 +/- 2.0) and in patients with HCM (23.3 +/- 3.3) com pared with normal subjects (20.3 +/- 2.3, P < .001 and P < .05, respectivel y). After sudden standing, LAAC increased significantly in normal subjects by 11%, in patients with HOCM by 24%, and in patients with HCM by 13% (P < .001). Similarly IVRT increased significantly in all study groups (P < .001 ). By using stepwise forward multiple linear regression analysis, we found that LAAC was associated with age, IVRT, and body moss index in the supine position and with diastolic blood pressure and IVRT in the standing positio n. Conclusions Left atrial contribution to left ventricular filling was increa sed after sudden changes of posture in normal subjects and in patients with HOCM or HCM.