Metabolic and functional evidence that retrograde warm blood cardioplegia does not injure the right ventricle in human beings.

BACKGROUND

Retrograde warm blood cardioplegia is now recognized as an effective method of myocardial protection, but concerns persist about its ability to adequately preserve the right ventricle.

METHODS AND RESULTS

A total of 75 patients in whom warm blood cardioplegia was continuously given through the coronary sinus were included in this three-part study. Part 1, which involved 30 patients undergoing coronary artery bypass grafting operations, was designed to assess whether the right ventricle incurred a greater degree of anaerobic metabolism than the left ventricle during warm arrest. Immediately before aortic unclamping, antegrade perfusion was resumed and, within 1 minute of washout, blood samples were simultaneously taken from the right ventricle and coronary sinus and assayed for lactate. There was no significant difference in lactate concentrations between the two sampling sites (right ventricle, 2.53 +/- 0.1 mmol/L; coronary sinus, 2.47 +/- 0.1 mmol/L). Part 2 focused on recovery of function. A complete set of postoperative hemodynamic measurements was obtained in 15 among the 30 patients enrolled in part 1 and compared with that obtained in 15 case-matched patients who received conventional cold antegrade crystalloid cardioplegia. Postoperative right ventricular stroke work index was not significantly different between the two groups (retrograde warm, 4.6 +/- 0.2 g.m-1.m-2; antegrade cold, 4.8 +/- 0.2 g.m-1.m-2). Part 3 was also targeted at functional end points but in 30 additional patients undergoing reoperative mitral valve replacement and consequently deemed to be at higher risk of right ventricular ischemia. Fifteen patients who received retrograde warm cardioplegia were compared with 15 case-matched control subjects in whom antegrade cold crystalloid cardioplegia was used. In keeping with data of part 3, postoperative right ventricular stroke work index was not significantly different between the two groups (retrograde warm, 6.9 +/- 0.4 g.m-1.m-2; antegrade cold, 7.7 +/- 0.5 g.m-1.m-2), nor was there a difference in clinical outcomes or biological recoveries of hepatic function.

CONCLUSIONS

Inadequate protection of the right ventricle associated with the use of retrograde warm blood cardioplegia does not appear to be a clinically founded concern since this technique preserves right ventricular function to the same extent as conventional antegrade cold cardioplegia does.