OPTIMAL MYOCARDIAL PROTECTION

  • 1 January 1978
    • journal article
    • research article
    • Vol. 84  (6) , 812-821
Abstract
The low mortality and perioperative infarction rates associated with aortocoronary bypass (ACB) make these criteria unsuitable for evaluating the adequacy of myocardial protection. Enzymatic and functional measurements were sensitive and specific indicators of myocardial injury. A prospective concurrent study of 78 patients undergoing triple ACB was conducted to evaluate the effectiveness of 3 popular methods of myocardial protection. Group I (32 patients) had a single dose of cold (4.degree. C) potassium cardioplegic (CPC) solution infused, inducing a mean myocardial temperature (MMT) of 31 .+-. 4.degree. C/min. Group II (23 patients) had multiple doses of CPC solution, inducing a MMT of 22 .+-. 2.degree. C/min. Group III (23 patients) had intermittent anoxic arrest at a MMT of 28 .+-. 1.degree. C. The groups had comparable clinical symptoms and catheterization findings. Serial measurements of cardiac specific creatine kinase (CK-MB) revealed a peak in enzymatic activity occurring 60 min following ACB. The highest CK-MB was significantly (P < 0.01) lower in Group II (25 .+-. 8 IU/l) than Groups I (50 .+-. 8 IU/l) and III (68 .+-. 14 IU/l). Myocardial performance was evaluated after ACB by serially measuring left ventricular stroke work index (SW) and left atrial pressure (LAP) in response to volume loading. The rise in SW was significantly (P < 0.01) greater in Group II (3.0 .+-. 0.7 gm .cntdot. m/m2 per mm Hg) than in Groups I (1.4 .+-. 0.7) and III (1.8 .+-. 0.9). The highest SW attained was higher (P < .01) in Group II (43 .+-. 7 gm .cntdot. m/m2) than Groups I (19 .+-. 6) and III (34 .+-. 8) at comparable LAP values (Group I: 20 .+-. 5 mm Hg; Group II: 18 .+-. 3; Group III: 18 .+-. 4). Post-operative clinical evaluation failed to differentiate the 3 groups. The more sensitive indices demonstrated the superiority of cold, multidose cardioplegia in providing optimal myocardial protection.