Modified heart-lung preparation for the evaluation of systolic and diastolic coronary flow in rats

A modified heart-lung preparation of the rat, which permits measuring systo lic and diastolic coronary flow separately and enables coronary compliance to be evaluated,is described. The systemic circulation was substituted by a shunt circuit, and the elastic properties of the arterial tree were mimick ed by a rubber balloon. Systolic and diastolic coronary flow was evaluated from the pulmonary and aortic flow signal. Integrated phasic pulmonary flow represented right ventricular stroke volume. Integrated phasic systolic ao rtic flow represented left ventricular stroke volume minus that volume flow ing into the coronary arteries during systole, because the aortic flow prob e had to be inserted distal to the origin of the coronary vessels. Because right and left, ventricular:stroke volume was identical under steady-state conditions,;the difference between systolic pulmonary and systolic aortic f low resulted in systolic coronary flow. Diastolic coronary ow was measured by means of the retrograde flow through the aortic flow probe. Coronary com pliance was calculated according to Frank's windkessel model from coronary resistance and from central diastolic aortic pressure, which decayed expone ntially after switching out the rubber balloon and the shunt circuit. It co uld be shown that the proportion of systolic to diastolic coronary flow dep ends on coronary compliance.