Myocardial beta-blockade as an alternative to cardioplegic arrest during coronary artery surgery

The authors' recent experimental work has demonstrated that myocardial prot ection using continuous coronary perfusion with warm beta-blocker-enriched blood avoids myocardial ischaemia and minimizes myocardial oedema formation , thus completely preserving left ventricle function. The purpose of this c linical study was to compare this alternative technique in terms of structu ral and functional myocardial protection with the routinely used crystalloi d Bretschneider cardioplegia. Sixty coronary artery surgery patients were r andomized to receive either crystalloid cardioplegia or continuous coronary perfusion with warm blood enriched with the ultra-short acting beta-blocke r esmolol. Cardiac function was evaluated using transoesophageal echocardio graphy (fractional area of contraction) and cardiac metabolism using arteri al-coronary sinus lactate concentration difference (D-a-CS(LAC)). From left ventricular biopsies, the authors determined myocardial oedema, heat-shock -protein-70, intercellular-adhesion-molecule and actin pattern. Patients wi th crystalloid cardioplegia received 3.6 +/- 0.8 grafts during 64 +/- 20 mi n cross-clamp time (beta-blocker: 3.5 +/- 0.9 grafts during 68 +/- 22 min: NS). Following cross-clamp removal crystalloid cardioplegia hearts released significant lactate amounts (D-a-CS(LAC) - 1.0 +/- 0.6 versus - 0.1 +/- 0. 2 mmol/litre in beta-blocker hearts; P < 0.05). In crystalloid cardioplegia hearts, myocardial water content increased from 82.1 +/- 2.1% pre-cardiopu lmonary bypass to 83.2 +/- 1.7% at the end of cardiopulmonary bypass (P < 0 .05); in beta-blocker hearts myocardial water content remained unchanged (p re-cardiopulmonary bypass: 82.3 +/- 1.9%: end of cardiopulmonary bypass: 82 .4 +/- 1.7%; NS). At the end of cardiopulmonary bypass, left ventricular bi opsies of beta-blocker hearts showed less structural damage as determined b y heat shock protein-70, intercellular adhesion molecule-I and deranged act in cross-striation pattern as compared with crystalloid cardioplegia hearts (P < 0.05). The postcardiopulmonary bypass fractional area of contraction was similar in both groups (beta-blocker: 65 +/- 14%; crystalloid cardiople gia: 62 +/- 16%); however, beta-blocker patients required less inotropic st imulation (dopamine: beta-blocker: 2.9 +/- 2.5 versus crystalloid cardiople gia: 5.0 +/- 2.3 mu g/kg per min; P < 0.05). The data suggest that continuo us coronary perfusion with warm esmolol-enriched blood results in better my ocardial protection compared with crystalloid cardioplegia. It is concluded that the concept of beta-blocker-induced cardiac surgical conditions may b e a useful alternative for myocardial protection during coronary artery sur gery. (C) 1999 The international Society for Cardiovascular Surgery. Publis hed by Elsevier Science Ltd. All rights reserved.