PATTERNS OF HUMAN MYOCARDIAL OXYGEN EXTRACTION DURING REST AND EXERCISE*

Abstract

Myocardial oxygen extraction has been studied by the technique of coronary venous catheterization and measurement of multiple coronary arteriovenous oxygen differences. Observations were made at rest (110) and during exercise (80). During rest, the control subjects had a normal frequency distribution of myo-cardial oxygen extraction percentages and coronary venous oxygen saturations, averaging 70 and 29%, respectively. Resting values remained essentially constant throughout exercise and rest post-exercise periods. Coronary insufficiency subjects had a lower mean myocardial oxygen extraction and a higher mean coronary venous oxygen saturation than did the controls at rest. During exercise myocardial oxygen extraction percentage increased and coronary venous oxygen saturation decreased significantly in 82% of the subjects. In congestive heart failure and in critical mitral stenosis, resting myocardial oxygen extraction percentage was increased when effective cardiac output was less than 3.0 liters per minute per m2. During exercise the pattern of myocardial oxygen extraction appeared to be governed by the presence or absence of coexisting coronary insufficiency.