CAN IMPROVED MICROVASCULAR PERFUSION BE ACHIEVED BY USING BOTH ANTEGRADE AND RETROGRADE CARDIOPLEGIA

Background. The complete and uniform distribution of cardioplegia to t he microvasculature of the heart is considered critical for myocardial protection. This study explores the hypothesis that enhanced microvas cular perfusion can be achieved by using both antegrade and retrograde cardioplegia. Methods. Infant piglet hearts (n = 15) were arrested wi th antegrade blood cardioplegia, excised, and fixed with 2.5% glutaral dehyde by retrograde perfusion. Hearts were then perfused retrograde w ith an inert intracapillary marker (NTB-2). Six of these hearts served as controls (group 1) to anatomically demonstrate the degree of capil lary perfusion achieved by the retrograde delivery route. Nine experim ental hearts (group 2) underwent a subsequent infusion of antegrade bl ood cardioplegia to wash out NTB-2 capillaries coperfused by both the antegrade and retrograde delivery techniques. Sections of the left ven tricular free wall and anterior-mid interventricular septum were taken and examined by light microscopy at four separate sites (average, 126 capillaries per section). Results. In control hearts, 98.9% +/- 0.9% of ventricular capillaries and 91.4% +/- 5.8% of septal capillaries we re perfused by retrograde cardioplegia. After antegrade blood cardiopl egia washed out group 2 hearts, 14.0% +/- 4.1% of capillaries in the v entricle still contained NTB-2, as did 12.5% +/- 5.4% of capillaries i n the septum. Conclusions. In this experimental model, antegrade blood cardioplegia did not coperfuse (and therefore washout) 12.5% to 14% ( p < 0.05) of capillaries perfused by retrograde cardioplegia. This sug gests that an additional 12.5% to 14% of capillaries within the myocar dium may receive cardioplegia if retrograde cardioplegia is used in ad dition to antegrade cardioplegia. We conclude that by combining both a ntegrade and retrograde cardioplegia, there is a potential for enhance d overall microvascular perfusion.