Retrograde cardioplegia does not adequately perfuse the right ventricle

Surgeons often rely primarily on retrograde cardioplegia for myocardial protection, because it provides adequate left ventricular perfusion even in the presence of coronary artery disease. Clinically, however, adequate right ventricular perfusion by retrograde delivery has not been demonstrated. Using intraoperative transesophageal echocardiography, we examined retrograde delivery of cardioplegic solutions by contrast echocardiography, which directly assesses myocardial perfusion. In 15 patients (seven having coronary bypass and eight having valve operations), 4 ml of sonicated Isovue medium was injected retrograde via a coronary sinus catheter. Myocardial perfusion was assessed quantitatively by visual inspection and back-ground-subtracted videodensitometric analysis. In five patients undergoing aortic valve replacement, right and left coronary ostial drainage was estimated during retrograde infusion. Before the aortic crossclamp was removed, myocardial oxygen extraction was calculated in all 15 patients by first delivering warm blood cardioplegic solution for 2 minutes in a retrograde fashion and then taking samples from the cardioplegia line and aortic root. This determined the oxygen extraction ratio across the myocardium at the end of retrograde delivery. Warm blood cardioplegic solution was next given antegrade, and 15 seconds later samples were taken from the cardioplegia line and a right ventricular (acute marginal) vein to determine the oxygen extraction ratio across the right ventricle. As assessed by contrast echocardiography, retrograde infusion resulted in almost four times more perfusion to the left ventricular free wall and septum than to the right ventricular free wall (74 +/- 2 versus 69 +/- 2 versus 20 +/- 2, p < 0.05). In those five patients with an aortotomy the right ostial drainage was less than 5 ml/min whereas left ostial drainage was estimated at 80 ml/min during retrograde administration. Oxygen extraction across the myocardium supplied by retrograde infusion was low after 2 minutes. Conversely, when antegrade cardioplegia was started, right ventricular oxygen extraction rose fourfold (42% +/- 5% versus 11% +/- 1%, p < 0.05), demonstrating that retrograde cardioplegia had not adequately perfused the right ventricular myocardium.

1. Retrograde cardioplegia provides poor right ventricular myocardial perfusion as assessed by contrast echocardiography and coronary ostial drainage. (2) This poor perfusion is inadequate to meet myocardial demands as demonstrated by the high right ventricular oxygen extraction after a prolonged retrograde infusion. (3) Therefore surgeons must not rely solely on retrograde cardioplegia for right ventricular myocardial protection. This concept is especially important if continuous warm blood cardioplegia is used, because myocardial requirements are then higher.