The microvascular distribution of cardioplegic solution in the piglet heart. Retrograde versus antegrade delivery.

The uniform distribution of cardioplegic solution to all areas of the microvasculature is considered critical for myocardial protection. Despite this, little information exists regarding the ability of retrogradely infused cardioplegic solution to perfuse the microvasculature of the heart. In this report, the microvascular distribution of retrogradely delivered cardioplegic solution was studied by means of a technique to quantitatively demonstrate capillary perfusion. Duroc piglet hearts were subjected to either antegrade (n = 4) or retrograde (n = 8) perfusion fixation with 2.5% glutaraldehyde and subsequently perfused with NTB-2 (an intracapillary marker). The results indicate that retrogradely delivered NTB-2 consistently perfused the anterior half of the intraventricular septum and the anterior and lateral free walls of the left ventricle but inconsistently perfused the posterior half of the intraventricular septum, the posterior wall of the left ventricle, and a small paraseptal region of the right ventricle. The remainder of the right ventricle was not perfused. In contradistinction, all regions of the heart were consistently perfused by the antegrade technique. In regions of the heart in which retrograde microvascular perfusion occurred, no statistical difference was found in the quantitative degree of capillary perfusion achieved by either the antegrade or retrograde technique. These results have important implications for planning strategies of myocardial protection and suggest that further investigation concerning the microvascular distribution of retrogradely delivered cardioplegic solution in human beings is merited.