SYSTOLIC TIME INTERVALS IN ATRIAL SEPTAL DEFECT

Diminished pulmonary vascular compliance (PVC) is believed to be a major determinant of the widened splitting of the second heart sound (S2) in atrial septal defect (ASD). However in association with the decreased PVC in ASD, the right ventricular ejection time (RVET) is prolonged. We tested the thesis that RVET shortens in the immediate post-op ASD period and that this shortening is directly associated with narrowed splitting of S2. Right and left pre-ejection periods (RPEP. LPEP) and ejection times (RVET, LVET) were measured pre-op both at cardiac catheterization (cath) and by echocardiographic semilunar valve recordings (echo) in 14 children with ASD. Repeat echo systolic time intervals (STI) were measured on the seventh post-op day. Pre-op and post-op phonocardiograms (phono) were recorded at the second left intercostal space. The maximum expiratory interval between the two high frequency components of S2 were recorded as A2-P2. All pre-op echo STI correlated highly with cath STI (r=0.87). RPEP changed from 0.073±.01 S.D. (seconds) pre-op to 0.065±.01 post-op; LPEP 0.073±.01 pre-op to 0.071±.01 post-op; and LVET 0.26±.01 pre-op to 0.27±.04 post-op. The RVET changed from 0.29±.04 pre-op to 0.24±.02 post-op.* The A2-P2 changed from 0.060±.007 pre-op to 0.014±.005 post-op.* Conclusions: We have demonstrated that RVET shortens in the early post-op period after ASD closure. Because PVC changes demand anatomic alterations, immediate shortening of A2-P2 suggests that RVET may be the major determinant of the width of splitting of S2. *p