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Impaired exercise tolerance after inferior vena caval interruption.

Four patients were evaluated for persistent dyspnea eight months to four years after inferior vena caval interruption for treatment of pulmonary emboli. Maximal exercise testing with gas-exchange analysis was performed. All patients attained less than 64 percent of predicted maximal oxygen uptake. Peak exercise heart rates were 85 percent or greater of predicted values. Arterial hypoxemia was not observed. The ratio of dead space to tidal volume (VD/VT) decreased with exercise, and the ratios of maximal exercise ventilation to maximal voluntary ventilation (VE/MVV) were less than 67 percent. These results suggest a cardiac rather than a ventilatory limitation to exercise. Inadequate venous blood return to the heart is the likely mechanism for the impaired exercise performances.