Ventricular performance in congenital left-to-right shunt: temporal Fourier analysis of gated blood-pool data.

Using global time-activity curves, the phase and amplitude at fundamental frequency were calculated, and emptying patterns of the right and left ventricles (RV,LV) were evaluated by phase difference [D(phase) = RV phase minus LV phase] and RV/LV amplitude ratio [R(amp)]. In 21 subjects with normal cardiac function, D(phase) was minimal (mean 2.2 +/- 6.1 degrees), regardless of heart rate, and R(amp) was distributed from 0.31 to 0.92 (mean 0.57 +/- 0.20). In 19 patients of ventricular septal defect (VSD), R(amp) remained within the normal range, whereas D(phase) became larger in proportion to the ratio of pulmonary-to-systemic blood flow, Qp/Qs (p less than 0.001). Especially, cases with Qp/Qs over 2.0 showed a significant RV phase lag. By contrast, nine patients with patent ductus arteriosus (PDA), showed no RV phase lag, but--particularly in cases with Qp/Qs greater than 2.0--R(amp) was smaller than normal (p less than 0.001). Thus this method is valuable for pathophysiologic investigation of diseases with L-to-R shunt, and can help in the noninvasive differential diagnosis between VSD and PDA.