Increased lung lymph transport without heart failure after coronary ligation in sheep

Pulmonary edema frequently accompanies acute myocardial infarction (MI). We measured pulmonary arterial (PAP), left atrial (LAP), and aortic pressures (AP),lung lymph flow (QL), and clearance of total serum protein and each of eight protein fractions in five anesthetized sheep before and after coronary artery ligation. After a stable base line of 1 h, ligation produced significant increases in LAP, QL, and clearance of total protein and four protein fractions, but no significant changes in PAP, AP, or lymph-to-plasma total protein concentration ratio (CSL/CSP). Variables returned to pre-MI levels within 2 h after occlusion. The ratio of wet to dry lung weight measured 2 h after ligation was within normal limits. Two sheep in which the time course of postligation LAP was duplicated by left atrial balloon inflation showed no change in QL. The QL changes seen cannot be caused by LAP increase alone without substantial decrease in CSL/CSP. Increased QL with high CSL/CSP is typical of increased lung vascular permeability, which is a plausible explanation of our results.