Abstract
A method of preparing an in situ papillary muscle in an excised, cross-circulated heart was developed and its basic contractile properties were studied. The preparation was instituted without any interruption of coronary perfusion with arterial blood. The coronary perfusion pressure was 103±8 (SD, 10 muscles) mmHg. The temperature of the perfusing blood was kept at 37°C. The preparation beat at a regular rate of 97±16beats/min. The maximal developed force of contraction, which was measured with a specially devised isometric force transducer, was 60±13g. When this was divided by the cross sectional area of the papillary muscle, it was 630±66g/cm2. The developed force and heart rate were stable for 4 to 6hr as long as anesthesia of the support dog was well maintained. When the coronary perfusion pressure was reduced to 50mmHg, the developed force decreased by 33±24%. On occlusion of both common carotid arteries of the support dog, the developed force increased by 38±17% while the coronary perfusion pressure was kept unchanged.
