Coupling of hemodynamic measurements with oxygen consumption during exercise does not improve risk stratification in patients with heart failure

Background: Measurement of peak V̇O₂ has become an accepted method to select patients for cardiac transplantation. Some investigators have suggested that the addition of exercise hemodynamic measurement can further enhance risk stratification because these measurements may identify patients with a noncardiac limitation to exercise. Methods and Results: Accordingly, we performed maximal bicycle exercise with respiratory gas analysis and hemodynamic measurements in 65 patients (47 men, 18 women) 53±10 years old (mean±SD) who underwent a transplant evaluation at Columbia Presbyterian Medical Center. Skeletal muscle oxygenation of the vastus lateralis during exercise was assessed with near-infrared spectroscopy. Exercise hemodynamic, ventilatory, and muscle oxygenation measurements were obtained in all patients. For each subject, a linear correlation was derived between V̇O₂ and pulmonary artery saturation (PA SaO₂). The slope of this relationship and a theoretical V̇O(2max) at a PA SaO₂ of 0% (V̇O₂ intercept) was derived. Baseline measurements were left ventricular ejection fraction, 22±9%, pulmonary capillary wedge pressure (PCWP), 16±10 mm Hg; cardiac index (CI), 2.1±0.5 L, min^-1 · m^-2, and PA SaO₂, 53±8%. The cardiac output response to exercise was categorized as normal or abnormal by comparison to the linear equation of peak V̇O₂ versus peak cardiac output as described by Higginbotham. Exercise measurements were peak V̇O₂, 12.1±3.0 mL · kg^-1 · min^-1; V̇O₂ intercept, 19.1±5.5 mL · kg^-1 · min^-1; PCWP, 31±11 mm Hg; CI, 3.8±1.3 L · min^-1 · m^-2, and PA SaO², 27±9%. Only 6% of patients exhibited a normal cardiac output response to exercise. Multivariate analysis was performed with peak V̇O₂, V̇O₂ intercept, skeletal muscle oxygenation at end exercise, and peak exercise hemodynamic variables. Only left ventricular stroke work and left ventricular stroke work index were shown to be predictive of survival. Conclusions: Addition of exercise hemodynamic measurements to noninvasive metabolic stress testing minimally improves risk prognostication in patients with severe heart failure.