Exogenous CGRP to improve coronary microcirculation after myocardial reperfusion during cardiopulmonary bypass

Objective To observe the changes of myocardial microcirculation after ischemia-reperfusion during cardiopulmonary bypass (CPB) and the effects of exogenous calcitonin gene related peptide (CGRP) on myocardial protection. Methods In vivo porcine models, 10 controls and 10 CGRP used animals (CGRP group) were performed on median sternotomy followed by a standard CPB. All the hearts were arrested for 45 minutes. In the CGRP group, 1?μg/kg CGRP was added into the cardioplegia, and reperfused into the aortic root before the removal of aortic clamp seperately. In both groups, myocardial microvascular perfusion, coronary arterial microvessel diameter and microvessel blood flow on the right atrium were detected by a laser doppler flowmeter and a contact microscope with TV monitor on five consecutive point of time ( before aortic clamping, 5, 30, 60 and 120 minutes after reperfusion). Results The myocardial microvascular perfusion was markedly decreased and coronary arterial microvessels became much thinner and pulsatile flow appeared when the heart was reperfused. It indicated the dysfunction of the coronary microcirculation. Myocardial microvascular perfusion was significantly higher and coronary arterial microvessel diameter was larger in the CGRP group on each point of time of reperfusion compared to those in the control group. In the CGRP group, microvessel blood flow also improved significantly than that in the control group during reperfusion. Conclusions Myocardial microcirculation disorders exist in cardiac ischemia reperfusion during CPB. As a component of cardioplegia, CGRP improves the myocardial microcirculation and could become a new, potent myocardial protector.