INFLUENCE OF CORONARY VENOUS RETROINFUSION AND VASODILATATION ON REGIONAL MYOCARDIAL BLOOD-FLOW MEASUREMENT WITH MICROSPHERES - AN ANALYSISOF MICROSPHERE LOSS FROM ISCHEMIC AND REPERFUSED PORCINE HEARTS

The influence of coronary venous retroinfusion and a vasoselective cal cium antagonist felodipine on the microsphere loss in a porcine model of myocardial ischaemia and reperfusion was studied. Sixteen open-ches t pigs underwent 45 min of myocardial ischaemia induced by occlusion o f the left anterior descending coronary artery followed by 4 h of repe rfusion. Either felodipine (felo-retro group, 7 nmol kg(-1), n = 6) or the corresponding amount of vehicle (vehicle-retro group, n = 5) was infused retrogadely into the coronary veins over 30 min, starting 5 mi n before reperfusion. In a third group, the same amount of felodipine was administered intravenously (felo-iv group, n = 5). Myocardial regi onal blood flow was measured with radiolabelled microspheres (phi = 15 mu m) injected before ischaemia to investigate a possible loss during ischaemia. In the felo-retro group, the apparent blood how in the isc haemic areas, expressed as a percentage of the corresponding Values in the non-ischaemic areas (%-flow), were 73 +/- 15, 73 +/- 11 and 75 +/ - 19 in the subendocardial, midmyocardial and subepicardial layers, re spectively. The corresponding percentage flows were 64 +/- 11, 70 +/- 11 and 62 +/- 9 in the vehicle-retro group and 75 +/- 18, 77 +/- 15 an d 76 +/- 11 in the felo-iv group. The differences between the groups w ere not statistically significant. It is concluded that in this open-c hest preparation microsphere loss observed in the ischaemic and reperf used myocardium is not increased by coronary venous retroinfusion or b y a concomitantly administered vasodilative agent like felodipine.