The quantitative relationship between longitudinal and radial function in left, right, and total heart pumping in humans

The total heart volume variation (THVV) during systole has been proposed to be caused by radial function of the ventricles, but definitive data for both ventricles have not been presented. Furthermore, the right ventricle (RV) has been suggested to have a greater longitudinal pumping component than the left ventricle (LV). Therefore, we aimed to compare the stroke volume (SV) generated by radial function to the volume variation of the left, right, and total heart. To do this, we also needed to develop a new method for measuring the contribution of the longitudinal atrioventricular plane displacement (AVPD) to the RVSV (RVSV AVPD ). For our study, 11 volunteers underwent cine MRI in the short- and long-axis planes and MRI flow measurement in all vessels leading to and from the heart. The left, right, and total heart showed correlations between volume variation from flow measurements and radial function calculated as SV minus the longitudinal function ( r = 0.81, P < 0.01; r = 0.80, P < 0.01; and r = 0.92, P < 0.001, respectively). Compared with the LV, the RV had a greater AVPD (23.4 ± 0.8 vs. 16.4 ± 0.5 mm), center of volume movement (13.0 ± 0.7 vs. 7.8 ± 0.4 mm), and, RVSV AVPD (82 ± 2% vs. 60 ± 2%) ( P < 0.001 for all). We found that THVV is predominantly caused by radial function of the ventricles. Longitudinal AVPD accounts for ∼80% of the RVSV, compared with ∼60% for the LVSV. This difference explains the larger portion of THVV found on the left side of the heart.