The mechanism of abnormal septal motion in atrial septal defect: pre- and postoperative study by radionuclide ventriculography in adults.

SUMMARY The mechanism of abnormal interventricular septal wall (IVS) motion in atrial septal defect (ASD) was studied by radionuclide cineventriculography before and within 2 weeks of ASD closure in 11 adult patients. Pre- and postoperative right ventricular/left ventricular volume ratio (RV/LV volume), LV peak filling rate (PFR) and LV ejection fraction (EF) were measured and compared with measurements in 13 normal adults. In normal subjects the configuration of the left ventricle was ovoid in diastole and the IVS curvature was convex toward the right ventricle. In all 11 ASD patients increased RV volume caused the IVS either to flatten during diastole or reverse its normal direction of curvature, becoming convex toward the left ventricle and resulting in a crescentic LV configuration. In early systole the IVS bulged anteriorly as the left ventricle reassumed its normal ovoid configuration and thereafter contracted normally. Postoperatively, RV volume decreased and both diastolic LV configuration and diastolic IVS curvature returned to normal in nine of the 11 patients. Postoperatively, mean RV/LV volume (± SD) decreased (3.6 ± 0.5:1 preop vs 2.1 ± 0.8:1 postop, p < 0.001; normal subjects 1.3 ± 0.1:1), PFR increased (2.13 ± 0.57/sec vs 3.16 ± 1.19/sec, p < 0.01; normal subjects 2.92 ± 1.28/sec) and EF was unchanged (0.62 ± 0.12 vs 0.69 ± 0.09; NS; normal subjects 0.66 ± 0.08). In three older patients a low LV EF returned to normal postoperatively. Systolic anterior IVS motion in ASD is caused by an initial abnormal curvature of the IVS during diastole to accommodate increased RV volume, and the IVS curvature returns to normal when this is relieved. The increased RV/LV volume ratio decreases and indexes of LV filling and ejection may improve early after ASD closure in adults.