Capillary filtration is reduced in lungs adapted to chronic heart failure:morphological and haemodynamic correlates

Objective: To determine pulmonary capillary filtration in experimental chro nic heart failure and to investigate some morphological and haemodynamic me chanisms that could account for reduced filtration in lungs adapted to chro nic heart failure. Methods: We studied pulmonary capillary filtration, vasc ular resistances and morphology in lungs from guinea-pigs adapted to chroni c heart failure. Heart failure was induced by banding of the ascending aort a (n=66) or sham control operation (n=78) in guinea-pigs which were studied at 150+/-8 days post-operation. Results: Reduced cardiac output, increased systemic vascular resistance and LV end diastolic pressure and increased L V and RV weight:body weight ratio (all P<0.05) indicated chronic heart fail ure at 5 months following aortic banding in guinea-pigs. Lung weight was in creased (61%, P<0.05) in heart failure compared with controls, but lung wat er content was reduced (5.5%, P<0.05), a reversal of the pattern seen acute ly. Studies in isolated perfused lungs demonstrated a reduced capillary fil tration coefficient (0.018+/-0.003 vs. 0.003+/-0.002 ml min(-1) mmHg(-1) g( -1), P<0.001), increased arterial (61%) and venous resistance (50%) in hear t failure lungs, P<0.05. Wall thickness:lumen ratio was increased in small (<250 pm) pulmonary arterioles (0.15+/-0.02 vs. 0.08+/-0.01) and venules (0 .06+/-0.005 vs. 0.04+/-0.002) in heart failure, P<0.01. Alveolar septal vol ume fractions (35.2+/-5.1 vs. 23.1+/-2.7) and septal:air-space volume ratio s (60.5+/-13.6 vs. 31.9+/-5.3) were also increased in heart failure, P<0.05 . Conclusions: Pulmonary adaptation to chronic heart failure is associated with vascular and alveolar remodelling that contributes to increased vascul ar resistance and reduced capillary filtration. These changes are likely to be important in mediating resistance to pulmonary oedema in chronic heart failure. (C) 2001 Elsevier Science B.V. All rights reserved.