Exercise-induced changes in left ventricular function after phlebotomy in patients with polycythemic COPD.

The exercise capacity of polycythemic COPD patients has been shown to improve after phlebotomy, possibly because of reduction of ventricular afterload by decreased blood viscosity, resulting in increased cardiac output. Ten patients with polycythemic COPD and mean hematocrit 62% were studied at rest and during exercise before and after reduction of mean hematocrit to 50% by repeated phlebotomy. Pulmonary function was evaluated by physiologic exercise testing on a bicycle ergometer. Cardiac function was evaluated by rest and exercise RNVG. Significant increase in exercise tolerance and maximal oxygen uptake at peak exercise, with significant reduction in mean systemic BP, were demonstrated. Ejection fractions did not change, but dV/dt for ejection from the left ventricle at peak exercise improved significantly. Mean SV counts, ESV counts, and EDV counts were measured and the fractional increase with exercise compared for prephlebotomy and postphlebotomy, assuming that resting volumes would not change. ESV counts and EDV counts were both proportionately, though not significantly, reduced postphlebotomy. The data tend to support the hypothesis that the afterload on the left ventricle is reduced, with resulting improved myocardial contractility and left ventricular function. Improved peripheral oxygen uptake may also be a factor.