QUANTITATIVE-EVALUATION OF LEFT-VENTRICULAR BYPASS IN REDUCING MYOCARDIAL ISCHEMIA

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 79  (5) , 523-533
Abstract
A controlled study was undertaken to evaluate the relationship between myocardial O2 consumption M.ovrhdot.VO2 and epicardial S-T segment improvement in an ischemic heart preparation during left ventricular (LV) bypass. Mongrel dogs (12) were prepared with left ventricular-aortic bypass, coronary sinus cannulation and a multiple point epicardial ECG technique. The left anterior descending coronary artery was ligated low (Group 1) or high (Group 2) after baseline studies. After ischemic baseline studies, increasing degrees of LV bypass were performed at a constant mean aortic pressure and heart rate. The final infarct size was determined by the nitroblue tetrazolium staining technique. In Group 1, a significant reduction in the average S-T segment elevation occurred during 50-59% of LV bypass during which M.ovrhdot.VO2 was reduced 10.9% from controls. A maximum S-T reduction of 75% occurred during LV decompression during which M.ovrhdot.VO2 was reduced 52.8% from controls. The final infarct size for Group 1 was 9.8 .+-. 0.9 g/100 g of LV. In Group 2, a significant reduction in S-T segment elevation occurred only after 90-99% LV bypass was achieved during which M.ovrhdot.VO2 was reduced 28.1% from controls. LV decompression produced a maximum S-T reduction of 63% during which M.ovrhdot.VO2 was reduced 50.2% from controls. The final infarct size for Group 2 was 21.1 .+-. 0.4 g/100 g of LV. Larger degrees of bypass are required to decrease the ischemic areas encountered in larger infarctions. LV decompression is most beneficial in reducing ischemic myocardium surrounding large infarctions.

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