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

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Abstract
The mechanism of abnormal interventricular septal wall (IVS) motion in atrial septal defect (ASD) was studied by radionuclide cineventriculography before and within 2 wk 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 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 diastolic LV configuration and diastolic IVS curvature returned to normal in 9 of 11 patients. Postoperatively mean RV/LV volume (.+-. SD) decreased (3.6 .+-. 0.5:1 preoperative vs. 2.1 .+-. 0.8:1 postoperative, P < 0.001; normal 1.3 .+-. 0.1:1), PFR increased (2.13 .+-. 0.57/s vs. 3.16 .+-. 1.19/s, P < 0.01; normals 2.92 .+-. 1.28/s) and EF was unchanged (0.62 .+-. 0.12 vs. 0.69 .+-. 0.09; nonsignificant; normals 0.66 .+-. 0.08). In 3 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; 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.