CARDIAC-PERFORMANCE OF AN ISOLATED HEART PREPARATION FROM THE DOGFISH (SQUALUS-ACANTHIAS) - THE EFFECTS OF HYPOXIA AND CORONARY-ARTERY PERFUSION

An isolated preparation of the heart of the spiny dogfish, Squalus acanthias, was developed that allowed control of filling and output pressures and perfusion of the coronary arteries. Cardiac output and stroke volume, but not frequency, were dependent upon atrial filling pressure. The mean maximum cardiac power output of 1.76 mW/g ventricle mass was achieved at high stroke volumes and moderate output pressures (29 cmH2O). When stroke volume was set at half of its measured maximum, increases in output pressure did not affect stroke volume up to pressures near 46 cmH2O, at which point cardiac power output was 1.4 mW/g ventricle mass. In the absence of coronary perfusion, hypoxic perfusion of the heart lumen reduced maximum power output by 38% at 58 +/- 3.4 torr and by 64% at 7.7 +/- 0.8 torr. Perfusion of the coronary circulation with air-saturated saline or red cell suspensions had no effect on hearts pumping air-saturated saline or hypoxic (PO2 = 58 +/- 3.4 torr) saline, but significantly increased the maximum power output of the hearts pumping severely hypoxic (PO2 = 7.7 +/- 0.8 torr) saline.