To the Editors: - We commend Wallace et al. for the excellent study about the effects of atenolol on postoperative myocardial ischemia. However, we have major concerns. First, it is highly unethical to randomize chronically beta-blocked patients with coronary artery disease into a group that will not receive beta-blockers before major surgery. Multiple studies have shown the deleterious effects from abrupt beta-blocker withdrawal, including tachycardia, ischemia, and infarction caused by upregulation of [Greek small letter beta]-receptors. [2,3]Although the authors noted no complications from abrupt beta-blocker withdrawal, it was poor practice to deliberately subject patients to this added risk.
Second, although the authors found that beta-blockers were associated with a decrease in perioperative ischemia and a decrease in long-term mortality, one must be careful not to conclude that decreasing perioperative ischemia decreases long-term mortality. Ischemia, as diagnosed by ST depression, is often caused by a supply/demand imbalance of oxygen delivery to the myocardium. This is in contrast to mortality from myocardial infarction, which is more likely caused by plaque rupture with sudden complete occlusion of an epicardial vessel. It is difficult to physiologically conceptualize, that decreasing myocardial ischemia perioperatively will result in a decrease in future mortality. Therefore, although an episode of ischemia may be a predictive marker of a possible myocardial infarction, prevention of an ischemia period, perioperatively or otherwise, has not been proven to decrease the incidence of myocardial infarction.
It is most likely that the beneficial effects of beta-blockers have not been fully elucidated, and prevention of myocardial infarction goes beyond preventing ischemia alone. For example, although beta-blockers decrease mortality after myocardial infarction, no other antiischemic medications have had similar results.
Finally, the authors' conclusion that perioperative treatment with atenolol reduces long-term mortality is in question. Although there was no difference in the use of cardiovascular medications between the two groups in the 2-yr postoperative period, there is no information regarding any difference in other interventions (e.g., PTCA CABG) that may have also contributed to a difference in survival between the groups. Also, there was a trend toward more ill patients in the placebo groups, which had a higher percentage of patients with definite coronary artery disease, previous myocardial infarction, diabetes mellitus (an independent predictor of death during 2-yr follow-up), untreated hypertension, and who underwent major vascular surgery. Although these trends were not statistically significant, the power was too low to conclude that the placebo group was not more ill than the atenolol group.
We agree with the recommendation to introduce perioperative beta-blockade in high risk patients for major surgery; however, we do not yet agree that the reduction in transient perioperative ischemia will have long-term benefits.
Stewart J. Lustik, M.D.
Ashwani K. Chhibber, M.D.
Assistant Professor; Department of Anesthesiology;
James P. Eichelberger, M.D.
Assistant Professor; Cardiology Unit; University of Rochester, School of Medicine and Dentistry; Rochester, New York; email@example.com
(Accepted for publication May 5, 1998.)