| Abstract: | Abstract. The circulatory adaptation to leg exercise in the supine and sitting positions with stepwise increased work loads was studied in twelve patients with signs of coronary heart disease. In four patients right heart catheterization was performed. Anginal pain appeared during exercise in both body positions in all patients, but at a lower work load and lower pulmonary oxygen uptake during supine exercise. Heart rate and systolic blood pressure were lower and the systolic ejection period was longer at the occurrence of angina during supine exercise. The calculated pressure-time per minute was significantly lower during exercise in the supine position. Catheterization data suggested a greater rise in left ventricular filling pressure with supine exercise. It is concluded that the differences in work tolerance for the two positions are partly due to a lower mechanical efficiency and may partly be secondary to the augmented venous return and increased left ventricular filling pressure observed during supine exercise. The augmented filling pressure will tend both to increase heart volume—and thereby augment myocardial oxygen requirements—and to compromise coronary perfusion and thus reduce myocardial oxygen supply during supine exercise. |
