The optimal delivery of cardioplegia to induce and maintain cardiac arrest is fundamen-tal to myocardial preservation during cardiac surgery. Traditional approaches utilizing intracoronary or intraaortic delivery of cardioplegia rely on antegrade flow through the epicardial coronary arteries to perfuse myocardial tissue. More recently, enthusiasm has grown for venous routes of cardioplegia delivery, relying on retrograde cardioplegia flow through the coronary veins. The common goal of these different approaches is adequate intramyocardial cooling and delivery of nutritive substrate to myocardial cells. Nonetheless, the extent to which basic anatomic and functional differences between the coronary arterial and venous systems result in differences in cooling and nutritive flow between these two techniques has heretofore not been well-defined. Furthermore, there may be differences in the regional distribution of cardioplegia flow as a function of the route of delivery, particularly in the presence of significant coronary artery disease.1-3 Clinically, such differences in physiology and flow distribution could have important implications for selecting the optimal route of cardioplegia administration.
This Chapter addresses the factors which may influence the selection of the method of cardioplegia delivery: the nutritive capacity and the regional myocardial distribution of retrograde and ntegrade cardioplegia. The first section focuses on recent data from our group,4,5 and compares the physiology of retrograde and antegrade cardioplegia delivery with respect to microvascular and nutritive flow, and their relation to myocardial cooling. Additionally, because the magnitude and regional distribution of cardioplegia flow may affect the choice of the route of delivery, the second section outlines the role that myocardial contrast echocardiography may have in the intraoperative assessment of cardioplegia flow to the myocardium.