Anticipation of bypass surgery: can it induce silent myocardial ischemia?

Psychological stress has been demonstrated to induce myocardial ischemia. To determine whether stressful events before a coronary artery bypass grafting procedure precipitate myocardial ischemia, silent or symptomatic, and whether this can have an effect on the prognosis, 26 patients were evaluated before a bypass operation with continuous Holter monitor recording. Specific events monitored were signing surgical consent, receiving preoperative medications, shaving and preparing, and transfer to the operating room. A positive Holter result was defined as an ST segment depression of 1 mm or more lasting one minute or longer. Six patients (23%) were found to have one or more episodes of substantial ST segment depression, with a total of ten episodes lasting 208 minutes recorded. All episodes were silent and not associated with an increase in mean heart rate. The majority of episodes occurred randomly, although three episodes did occur between 5 and 6 AM at the time of transport to the operating room. This appeared to be related more to the circadian rhythm than to the stress of transport. No perioperative or postoperative myocardial infarctions occurred, and all patients were alive at 30 days. In conclusion, silent myocardial ischemia present in the immediate preoperative period does not appear to be related to specific preoperative events. Frequency of early morning ischemia may warrant changes in the medication schedule to provide additional protection during these hours.