Relations between coronary flow and work of the heart

¹ Department of Physiology, Instituto Nacional de Cardiología de Mexico, Mexico, D.F.

The mean total coronary flow of dog hearts, perfused via the aorta by a donor dog, was recorded. The amount of work performed by the recipient heart was varied within wide ranges. Its aortic pressure was also varied, thus determining changes in the coronary flow. When the frequency of stimulation of the heart and the aortic pressure are maintained constant, changes of the work performed do not result in changes of the coronary flow. When the working conditions of the heart are maintained constant, changes of the coronary flow do not cause any variations of the amount of work performed. The work performed does not affect the pressure-flow relationships. It is concluded that with adequate circulation there is a wide margin of safety in the oxygen supply to the ventricle. The heart can increase its work importantly without producing or requiring an increase of its coronary flow.