STUDIES OF RETROGRADE CARDIOPLEGIA .1. CAPILLARY BLOOD-FLOW DISTRIBUTION TO MYOCARDIUM SUPPLIED BY OPEN AND OCCLUDED ARTERIES

  • 1 April 1989
    • journal article
    • research article
    • Vol. 97  (4) , 605-612
Abstract
This study defines the nutritive (i.e., capillary) distribution of blood cardioplegic solutions delivered via retrograde and antegrade techniques to muscle supplied by open and occluded coronary arteries where myocardial segments are in jeopardy of inadequate cardioplegic protection. Open-chest anesthetized dogs were studied by mixing radioactive microspheres (15 .+-. 5 .mu.m) with a blood cardioplegic solution and administering cardioplegia either into the coronary sinus or into the proximal aorta with the left anterior descending coronary artery open or occluded (30% .+-. 2% area at risk). Nutritive flow (i.e., percentage of delivered 15 .mu.m microspheres trapped in myocardial capillaries) during retrograde infusions averaged 65% versus 87% with antegrade cardioplegia (p < 0.05). Retrograde and antegrade cardioplegic nutritive flow to all left ventricular regions was comparable with the left anterior descending coronary artery open (65 versus 82 ml/m100 gm/min, p > 0.05), and both methods provided preferential hyperperfusion of subendocardial muscle (endocardial/epicardial ratios 1.6 and 1.5, respectively). Nutritive flow to muscle supplied by the occluded left anterior descending coronary artery was preserved better by retrograde than antegrade cardioplegia (35 versus 5 ml/100 g/m/min, p < 0.05). Preferential subendocardial hyperperfusion was maintained during retrograde cardioplegia (52 ml/100 gm/min, endocardial/epicardial ratio 1.6), but flow was redistributed away from subendocardial muscle with antegrade cardioplegia (< 2 ml/100 gm/min, endocardial/epicardial, 0.29, p < 0.05). Left ventricular flow was reduced markedly during retrograde infusion with the left anterior descending coronary artery open or occluded (23 and 12 ml/500 gm/min), but septal cooling was superior to antegrade cardioplegia (15.degree. .+-. 1.degree. C versus 20% .+-. 3%, p < 0.05) despite near-normal antegrade septal flow (the left anterior descending coronary artery was ligated beyond the first septal branch). Right ventral nutritive flow was only 7 ml/100 gm/min during retrograde coronary sinus perfusion and was maintained normally with antegrade cardioplegia. We conclude that retrograde cardioplegia is (1) superior to antegrade cardioplegia in delivering nutritive flow to areas supplied by occluded arteries, (2) maintains perferential subendocardial flow to subendocardial muscle in jeopardy of inadequate cardioplegia protection during occlusion of the left anterior descending coronary artery, (3) produces excellent left ventricular septal cooling despite reduced nutritive flow, and (4) is distributed poorly to the right ventricle.

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