Intravascular and extravascular pulmonary fluid volumes during chronic experimental left ventricular dysfunction

Abstract

To assess the effects of chronic left ventricular (LV) dysfunction on intravascular pulmonary blood volume (PBV) and extravascular lung water (EVLW) lung fluid volumes, 56 dogs were evaluated by means of double-indicator dilution techniques. PBV and EVLW were measured in seven control dogs, in eight dogs 4 hours after the production of left heart dysfunction, and then in three additional groups of dogs (n = seven in each group) 7, 14, and 30 days after the production of LV dysfunction. Twenty dogs were excluded because we were unable to produce elevations in LV end-diastolic volume >25 mm Hg. EVLW was measured using heat as the diffusible indicator, and electric shock was used to create heart block and myocardial scarring in order to produce LV dysfunction. Plasma volume was calculated prior to death by means of radioiodinated albumin. In the remaining animals, electric shock acutely and chronically elevated LV end-diastolic pressure (control 2.3 ± 1.0 mm Hg; postshock pressure >25 mm Hg). PBV increased initially after cardiac failure and remained so as time progressed, although it represented a smaller fraction of the plasma volume as time passed (11.2 ± 2.1% control, 15.9 ± 3.4% at 4 hours after failure, and 12.6 ± 2.0% at 7 days; the former p < 0.005 vs control, the latter p < 0.01 vs control). EVLW increased as time progressed, in consort with small but progressive increases in left atrial pressure. Thus, we conclude that the effects of acute and chronic LV dysfunction on pulmonary circulation are significantly different. During chronic dysfunction, fluid retention results in expansion of total blood volume, with concomitant increases in EVLW. During acute dysfunction blood is shifted from the peripheral to the central circulation and PBV represents a greater proportion of total blood volume. Moreover, there is a gradual decline in PBV over time after the creation of LV dysfunction, although it still remains elevated compared to control values.