CHARACTERIZATION OF SYSTEMIC OXYGEN-TRANSPORT IN END-STAGE CHRONIC CONGESTIVE-HEART-FAILURE

Chronic congestive heart failure (CHF) is characterized by low cardiac index (CI) and low systemic oxygen delivery (Do(2)), which frequently are associated with lethal cardiogenic shock after acute myocardial i nfarction. Nevertheless, patients with severe CHF are able to survive with these low levels of systemic Do(2) and Cl. It was hypothesized th at patients with CHF survive low CI and Do(2) by downregulation of glo bal metabolism and resting oxygen consumption (Vo(2)) and a concomitan t increase in systemic oxygen extraction ratio (o(2)ER). Therefore the objective of this study was to characterize the resting pattern of sy stemic oxygen transport (o(2)T) and utilization in patients with stabl e CHF. Seventeen patients with CHF (New York Heart Association functio nal class III or IV) for greater than or equal to 3 months and with le ft ventricular ejection fraction (EF) <25% and whose condition was sta ble with conventional oral therapy were studied. The control group com prised 10 subjects (NYHA class I) who had coronary angiography and who were found to have normal left ventricular function and EF >60%. Subj ects underwent right-heart catheterization for measurement and calcula tion of hemodynamic and o(2)T variables (Vo(2), Do(2), and o(2)ER). Th ere were no significant differences in mean age (67 +/- 6 vs 64 +/- 17 years) or gender ratio (male:female 14:3 vs 7:3) between CHF and cont rol groups, respectively. The cause of CHF was ischemic in 13 and idio pathic in 4 patients. There were 9 patients in NYHA class III and 8 in class IV. Although heart rate (84 +/- 15 vs 80 +/- 15 beats/min) and mean arterial pressure (89 +/- 19 vs 99 +/- 10 mm Hg) were similar, pu lmonary capillary wedge pressure was significantly raised (26 +/- 9 mm Hg, vs 10 +/- 3 mm Hg, p < 0.001) in CHF vs control, respectively. Cl (1.7 +/- 0.4 L/min/m(2) vs 2.9 +/- 0.3 L/min/m(2), p < 0.001), left v entricular EF (17% +/- 6% vs 70% +/- 10%, p < 0.001), systemic Do(2), (279 +/- 52 ml/min/m(2) vs 531 +/- 86 ml/min/m(2), p < 0.001), Vo(2) ( 106 +/- 14 vs 150 +/- 28, p < 0.001), and mixed venous oxygen saturati on (60 +/- 6 vs 67 +/- 4, p < 0.02) were significantly reduced in CHF group vs control, respectively. In conclusion, end-stage CHF is charac terized by decreases in CI and Do(2) that are associated with a signif icant reduction in systemic Vo(2) and an increase in o(2)ER. This leve l of Vo(2) would be lethal in other clinical shock states; however, do wnregulation of metabolic and oxygen demands (or hibernation) may be a n adaptive response in end-stage CHF to enhance survival.