Effect of Site of Shunt

Quantitative cineangiocardiographic technics have been utilized to determine left ventricular (LV) and left atrial (LA) volumes and LV muscle mass in 58 patients with isolated ventricular septal defect, 14 of whom were infants less than 2 years old, and in 25 patients with isolated patent ductus arteriosus, 13 of whom were infants. Patients were divided according to the degree of left-to-right shunt into small (< 35%), moderate (35 to 50%), and large (> 50%) shunt groups. Data obtained in both the VSD and the PDA groups were compared with normal values. Left ventricular end-diastolic volume and mass and LA maximal volumes in the patients of both groups who had shunts of 35% or more were greater than normal and showed a linear increase with increasing left-toright shunt. The LV ejection fraction was decreased from normal in infants with either VSD or PDA and a shunt of more than 50%. This variable was normal in older children with either VSD or PDA. Patients with an aortic or a ventricular defect and equivalent shunts did not differ significantly in terms of LV end-diastolic volume, LV mass, LV ejected fraction, or LA maximal volume, normalized for body surface area. Patients with a patent ductus demonstrated the following differences when compared with patients with ventricular septal defect: (1) elevated LV end-diastolic pressure, (2) elevated LV end-diastolic stress, and (3) elevated value for LV mass (/m2 BSA) per degree of shunt in children over 2 years of age with a patent ductus (P < 0.05). These results indicate that left ventricular distensibility is decreased in patients with aortic left-to-right shunts compared to that in patients with ventricular left-to-right shunts of equivalent magnitude.