Coronary flow reserve and oxygen metabolism of the right ventricle

The flow reserve of the right coronary artery (RCA) and myocardial oxygen extraction are important tractors in any investigation of the mechanisms of impaired right ventricular function. The present study induced brief coronary occlusions and examined the effect on right coronary blood flow in normal dogs, and the effect on myocardial oxygen metabolism in dogs with right ventricular hypertrophy (RVH). Right coronary flow reserve, represented by occlusion duration causing a half maximum dilatation (T1/2), was greater in the RCA than in the left anterior descending coronary artery of normal dogs; 11.4 +/- 2.3 sec vs 5.9 +/- 1.4 sec. Myocardial oxygen extraction ratio (EO2) of the right ventricle (RV), 51.3 +/- 1.6%, was significantly (p less than 0.05) lower than the index of the left ventricle (LV), 60.6 +/- 1.0%, and the extraction of the RV increased significantly in association with an increase of myocardial oxygen demand. In dogs with RVH caused by chronic banding of the pulmonary artery, this dominant oxygen reserve was lost: the EO2 of the hypertrophied RV was high compared with the EO2 of the normal RV (57.3 +/- 3.4% vs 51.3 +/- 1.6%, p less than 0.05), and no further increase in EO2 was observed in the hypertrophied RV in response to the elevation of the myocardial oxygen requirement. Oxygen usage per 100g of the RV for a certain level of overall RV work, rate-pressure product, was significantly (p less than 0.02) lower in the hypertrophied RV (0.00054 mlO2/beat.mmHg) than in the normal RV (0.0012 mlO2/beat.mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)