FETAL LAMB PULMONARY HYPOPLASIA - PULMONARY VASCULAR AND MYOCARDIAL ABNORMALITIES

Neonatal pulmonary hypoplasia resulting from a congenital diaphragmati c hernia (CDH) produces hemodynamic changes and morphologic abnormalit ies of the pulmonary vasculature. To characterize the myocardial and p ulmonary vascular status of the fetus with pulmonary hypoplasia, we st udied four chronically instrumented, near-term fetal lambs with pulmon ary hypoplasia, induced by producing a diaphragmatic hernia. We found an elevation in the pulmonary arterial pressure (control, 43.8 +/- 5.9 mm Hg; CDH, 58.8 +/- 9.1 mm Hg; p < 0.05), an elevation in the system ic arterial pressure (control, 43.8 +/- 0.48 mm Hg; CDH, 58.6 +/- 6.7 mm Hg; p < 0.05), and an elevation in the pulmonary vascular resistanc e (control, 0.47 +/- 0.11; CDH, 3.87 +/- 1.9; p < 0.05). In addition, though the total pulmonary blood flow was reduced (control, 83.5 +/- 3 2.9 mL/min; CDH, 22.2 +/- 17.6 ml/min; p < 0.05), the blood flow reduc tion was proportional to the reduction in the lung mass (control, 79.8 +/- 28.1 in flow per 100-g lung weight; CDH, 85.4 +/- 71.7). The in crease in the pulmonary vascular resistance in relation to the unit lu ng mass (control, 0.55 +/- 0.33; CDH, 0.99 +/- 0.5) was not as pronoun ced as its increase in relation to the total pulmonary blood flow. Myo cardial enlargement occurred (control weight, 5.2 +/- 0.8 g; CDH weigh t, 8.4 +/- 0.4 g; p < 0.05) and right ventricular wall thickness was i ncreased (control, 0.96 +/- 0.31 mm; CDH, 1.78 +/- 0.53 mm; p < 0.05), possibly resulting from increased myocardial wall stress, as indicate d by an increased subepicardial-subendocardial blood flow ratio (contr ol, 1.4 +/- 0.29; CDH, 1.7 +/- 0.13; p < 0.05).