The drop of residual right ventricular pressure 24 hours after conservative infundibulectomy in repair of tetralogy of Fallot.

Because of late complications such as right ventricular (RV) dysfunction and sudden death after tetralogy repair, a modification in the technique of total repair of tetralogy of Fallot is sought. In this study a shorter than usual conal incision and limited division of only the parietal muscle bands were utilized in 17 patients. The mean RV pressure at the end of the operation was 84 mm Hg; 24 hours later it had dropped to 55 mm Hg. The mean RV/LV pressure ratio at the end of the operation was 0.85, and 24 hours later it was 0.48. Pressure measurements were also taken at the end of the operation, at four predetermined points along the RV outflow tract. It was found that 40% of the average residual obstruction was located at the level of the infundibular ostium, 50% at the level of the conus, and 10% at the pulmonary valve. It is concluded that a 40% drop in the RV/LV pressure ratio can be anticipated to occur in less than 24 hours in cases in which (1) the contractility of the infundibular ostium and conus is preserved by conservative infundibulectomy and (2) there is a residual obstruction at a muscular level. This is on condition that the passage between the crista and the anterior conal wall is of adequate size.