Natural and post-operative history of pulmonary vascular obstruction associated with ventricular septal defect.

The natural history of pulmonary vascular obstruction in VSD associated with PH was studied by measuring PVR before and after injection of tolazoline 1 mg/kg. Organic pulmonary vascular obstruction (PVO) was minimal in infancy, but increased linearly progressively with advancing age, and average rate of increase in PVR after tolazoline was 1 unit.m2/year. The rate of increase in PVR after tolazoline in Eisenmenger complex was variable and ranged between 0.7 to 4 unit.m2/year in most cases. Analysis of 7 cases of post-operative late death due to PVO revealed that usually these cases were over 5 years of age at operation, and pre-operative PVR was more than 12 unit.m2. Reduction of PVR was confirmed post-operatively in most of these cases whose pre-operative PVR before and after tolazoline were les than 8 unit.m2 and 7 unit.m2 respectively. Early surgical repair is indicated in VSD and PH to prevent progress of PVO.