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 infarction. Nevertheless, patients with severe CHF are able to survive with these low levels of systemic Do(2) and Cl. It was hypothesized that patients with CHF survive low CI and Do(2) by downregulation of global metabolism and resting oxygen consumption (Vo(2)) and a concomitant increase in systemic oxygen extraction ratio (o(2)ER). Therefore the objective of this study was to characterize the resting pattern of systemic oxygen transport (o(2)T) and utilization in patients with stable CHF. Seventeen patients with CHF (New York Heart Association functional class III or IV) for greater than or equal to 3 months and with left ventricular ejection fraction (EF) <25% and whose condition was stable with conventional oral therapy were studied. The control group comprised 10 subjects (NYHA class I) who had coronary angiography and who were found to have normal left ventricular function and EF >60%. Subjects underwent right-heart catheterization for measurement and calculation of hemodynamic and o(2)T variables (Vo(2), Do(2), and o(2)ER). There 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 control groups, respectively. The cause of CHF was ischemic in 13 and idiopathic 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, pulmonary 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 ventricular 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 saturation (60 +/- 6 vs 67 +/- 4, p < 0.02) were significantly reduced in CHF group vs control, respectively. In conclusion, end-stage CHF is characterized by decreases in CI and Do(2) that are associated with a significant reduction in systemic Vo(2) and an increase in o(2)ER. This level of Vo(2) would be lethal in other clinical shock states; however, downregulation of metabolic and oxygen demands (or hibernation) may be an adaptive response in end-stage CHF to enhance survival.