Hemodynamic correlates of clinical severity in isolated ventricular septal defect.

To test the hypothesis that the clinical assessment of severity in ventricular septal defect would be more related to variables which define tissue oxygen delivery than variables which define the left-to-right shunt, cardiac catheterization data from 40 children < 3 years of age were assessed. Variables which were considered indicative of clinical severity included the need for digoxin and diuretics, resting heart rate, and severity of growth failure. Variables measured at cardiac catheterization, including those which related to oxygen transport, and assessment of left-to-right shunt, were considered independently. Patients receiving digoxin and diuretics were more tachycardic (142 +/- 18 vs. 111 +/- 26 beats/min, p < 0.001) and had lower superior vena cava oxygen saturation (64 +/- 6 vs. 69 +/- 5%, p < 0.01). Variation in heart rate (r2 = 0.46) was best explained by oxygen consumption, hemoglobin concentration, cardiac index, and pulmonary vascular resistance. Variation in growth failure (r2 = 0.15) was related only to the left ventricular forward stroke index. These data suggest that variables related to oxygen delivery, including oxygen consumption, hemoglobin concentration, cardiac index, forward stroke index, and superior vena cava oxygen saturation, are the major contributors to the clinical assessment of severity in ventricular septal defect.