Intermittent, rate-dependent left bundle branch block can occur during the perioperative period without underlying myocardial infarction, though it requires careful monitoring to rule out ischemia.
Rate-dependent LBBB may occur without MI under anesthesia; leaves open need for prospective perioperative conduction studies.
We has experienced a case who had normal preoperative ECG findings, however, developed a left bundle branch block (LBBB) in preinduction period of anesthesia. A 73-year-old male, with chief complaint of melena, was diagnosed as cancer of the sigmoid colon. He had no remarkable medical history nor abnormalities in preoperative laboratory findings. After entering the operating room to undergo elective resection of the sigmoid colon, lead II ECG tracing prior to mesthesia induction revealed a LBBB. However, it changed to normal sinus rhythm snddenly during our investigation of the cause. Following preoxygenation, anesthesia was induced with thiopental, intubated with succinylcholine, and maintained with nitrous oxide 66 percent in oxygen and halothane. During operation, a LBBB pattern occurred whenever heart rate increased to over 110 per minutes (rate dependent LBBB). No change in blood pressure was accompanied by these episodes.Recovery from anesthesia was uneventful. Post operative holter ECG showed intermittent LBBB with no change in GOT, GPT, CPK etc. Though LBBB itself is a relatively benign dysrhythmia, it is significant during anesthesia, because it may indicate a possible development of myocardial infarction. It is difficult to diagnose myocardial infarction on the ECG in the presence of a LBBB.
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Yokoyama et al. (1989) studied this question.
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