SYSTOLIC TIME INTERVALS IN ATRIAL SEPTAL DEFECT

Abstract

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<0.001

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