To the Editor:—
In a recent study by Booth et al. , 1the authors noted improved left-ventricular function resulting from intravenous esmolol infusion in a model of myocardial ischemia–reperfusion injury and cardiopulmonary bypass (CPB). We read this article with great interest, as it contributes further evidence of the cardioprotective properties of β-blockade in an experimental model resembling the conditions of emergent coronary artery bypass grafting (CABG) surgery. However, we beg to differ with the authors’ statement that “a paucity of studies exist on effectiveness, rationale, and/or mechanisms underlying the use of βAR [β-adrenergic receptor] antagonists in this setting” (i.e. , CABG surgery during acute myocardial ischemia).
We would like to remark that the intraoperative use of esmolol is now a well established technique of myocardial protection that was clinically introduced 10 yr ago. 2A number of clinical studies have investigated the impact of intraoperative esmolol administration on outcome. 3–6We also take issue with the authors’ perception that “most animal models to date have focused on CPB alone. The criticism of those models is that no human undergoes CPB alone, and therefore, the model does not reflect CABG surgery.”
A number of experimental studies, some of which were conducted by our group, have investigated the impact of esmolol in models of CPB and acute myocardial ischemia–reperfusion injury and showed that esmolol improved myocardial function and reduced infarct size. 7–9We believe that the discussion in this otherwise excellent paper by Booth et al. 1suffers significantly from the failure to consider this previous work.
Another detail of concern is the combination of esmolol and cold crystalloid cardioplegia in the treatment group, which makes no sense from a cardiac surgeon's point of view. Intraoperative myocardial protection with esmolol is considered an alternative rather than an adjunct to cardioplegic arrest. In fact, combining both principles sacrifices the major advantages of the esmolol technique, such as the avoidance of additional global myocardial ischemia and prevention of crystalloid perfusion–induced myocardial edema.
