Pulmonary edema formation after myocardial infarction and coronary reperfusion: Intravascular and extravascular pulmonary fluid volumes. IV.

Two studies were performed to assess the importance of coronary reperfusion on pulmonary capillary endothelial permeability in 34 anesthetized dogs. The response of intravascular pulmonary blood volume (PBV) and extravascular lung water (EVLW) was examined using indicator-dilution and postmortem (wet weight/dry weight) techniques. In the first study, six dogs served as sham controls, seven were occluded (LAD) for 45 min, and seven occluded for 45 min and reperfused for 15 min. While PBV was similar in each group, EVLW was greater in the reperfused than nonreperfused dogs (9.5 ± 0.7 cc/kg vs 8.1 ± 0.8 cc/kg; P < .05), and both occluded groups were greater (P < .01) than the control animals (7.0 ± 1.0 cc/kg). Similar trends in postmortem wet weight/dry weight data were observed when compared with the in vivo EVLW data. In a second study of 14 open-chest dogs, an LAD ligation was held for 45 min in 14 dogs. In seven dogs, reperfusion was allowed for 15 min. A left atrial (LA) balloon was then inflated in all 14 dogs, increasing left atrial pressure to 25 mmHg in each dog for 90 min. Once again, PBV was similar in both groups, but EVLW was greater at the matched level of LA pressure elevation (14.6 ± 3.2 cc/kg nonreperfused vs 18.7 ± 4.1 cc/kg reperfused dogs; P < .01). Again, postmortem data confirmed these data. Thus, we conclude coronary occlusion accelerates EVLW formation independent of LA pressure. Edema formation is worsened by coronary reperfusion, suggesting that the washout of myocardial toxins from the ischemic myocardium alters endothelial permeability. A possible clinical corollary of this study is that coronary reperfusion in infarcting patients with elevated left atrial pressure and necrotic myocardium may transiently promote the production of pulmonary edema. At low filling pressures, the increase in EVLW with reperfusion would not be likely to be clinically apparent or important.