THE REGIONAL CAPILLARY DISTRIBUTION OF RETROGRADE BLOOD CARDIOPLEGIA IN EXPLANTED HUMAN HEARTS

Warm retrograde blood cardioplegia is frequently used for myocardial p rotection, despite experimental studies questioning the adequacy of ca pillary flow to the right ventricle and septum. The capillary distribu tion of retrograde blood cardioplegia in the human heart is unknown, H earts from eight transplant recipients with the diagnosis of idiopathi c or dilated cardiomyopathy were arrested in situ with cold blood card ioplegia and excised with the coronary sinus intact. Within 20 minutes of explantation, colored microspheres mixed in 37 degrees C blood car dioplegia were administered through the coronary sinus at a pressure o f 30 to 40 mm Hg for 2 minutes. Twelve transmural myocardial samples w ere taken horizontally at the level of midventricle and apex to determ ine regional capillary flow rates. When retrograde warm blood cardiopl egia was administered at a rate of 0.42 +/- 0.06 ml/gm/min, the left v entricle, the septum, the posterior wall of the right ventricle, and t he apex consistently received capillary how rates in excess of their m etabolic requirements. The capillary perfusion of anterior and lateral walls of the right ventricle was marginally adequate to sustain aerob ic metabolism. In explanted human hearts, retrograde blood cardioplegi a provides adequate capillary flow to the left ventricle, the septum, the posterior wall of the right ventricle, and the apex; however, capi llary flow to the anterior and lateral walls of the right ventricle is marginal. This study delineates the tenuous balance between supply an d demand for right ventricular protection with warm continuous retrogr ade blood cardioplegia.