HTK液による逆行性心筋保護法の実験的検討

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Recently, cardioplegia has been widely employed for myocardial protection during cardiac surgery. Critical coronary artery stenosis and occlusions may result in inhomogeneous distribution of antegradely delivered cardioplegic solution and consequently poor local myocardial protection. Retrograde administration of cardioplegia through the coronary sinus is increasingly being used as an alternative delivery method. Histidine-Tryptophan-Ketoglutarate (HTK) solution originates from Bretschneider solution which was introduced in 1964 by Bretschneider as a so-called intracellular type of cardioplegic solution. But the method of retrograde HTK cardioplegia is not well established. The hypothetical premise underlying our study was that retrograde cardioplegia would result in an equally good recovery of cardiac function as antegrade cardioplegia, following myocardial ischemia. Isolated pig hearts were perfused in Krebs-Henseleit bicarbonate buffer (KHB) solution at 37℃ using the Langendorff model. They were given a single dose of 4℃ HTK solution by various methods (n=7 in each group), subjected to 2 hours of global ischemia at temperatures of 24℃ (Group I-III) and 20℃ (Group IV). Group I recieved antegrade infusion via the aortic root for 10 minutes (the mark was 500 ml). Group II and Group IV recieved retrograde infusion via the coronary sinus for 10 minutes at 65 cm H2O pressure. Group III recieved retrograde infusion (same as Group II), the infusion volume was 500 ml (equal to antegrade infusion volume). Infusion volume of Group II and Group IV was below half of that in Group I. Infusion time of Group III was 1430±114 seconds. The percent recovery of left ventricular developed pressure (LVDP) was 102.2±7.0% in Group I, 78.0±3.6% in Group II, 112.0±7.4% in Group III and 98.4±4.4% in Group IV. Group II was significantly lower than Group I (p<0.05), and peak positive dP/dt (+dP/dt) and peak negative dP/dt (-dP/dt) were lower in Group II, too. Tissue water content of the right ventricle increased significantly in Group II (p<0.05), and had a tendency to increase in Group III and Group IV. With ultrastructural changes of Group II, the mitochondria of myocytes ?showed a swelling and fragmentation of cristae. But there were no significant differences in myocardial high energy phosphates among all Groups. From these results, as shown by Group III and Group IV, we deduced that retrograde cardioplegia of HTK solution results in adequate preservation of ischemic heart. However, the clinical use of this Group III method is controversial because the long infusion time necessary to achieve complete myocardial preservation causes a prolongation of the operation time. Finally, we conclude that retrograde HTK cardioplegia is appropriate when used together with antegrade infusion or in an extremely low temperature operation. Further studies are necessary to determine the effects of retrograde HTK cardioplegia on the in vivo model using cardiopulmonary bypass.
札幌医科大学の論文
1997-12-01

HTK液による逆行性心筋保護法の実験的検討

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