Left bundle branch block (LBBB) can be caused by cardiovascular abnormalities, and its existence makes the diagnosis of acute myocardial ischemia or infarction difficult using electrocardiography (ECG). Here, we describe our experience providing anesthetic management to a patient who developed a transient complete LBBB (CLBBB) during the perioperative period.
A 58-year-old woman was scheduled to undergo a biopsy for oral floor cancer under general anesthesia. During the preoperative screening, a 12-lead ECG showed evidence of a CLBBB and tachycardia (106 beats/min), which had not been observed on previous ECG examinations. To check for the existence of underlying cardiovascular diseases, echocardiography and coronary angiography were performed. Since these examinations did not show evidence of myocardial ischemia and suggested normal cardiac function, the general anesthesia was performed as scheduled. Upon arrival in the operating room, an ECG showed normal conduction. During the general anesthesia, however, an LBBB suddenly appeared when the heart rate (HR) increased to 97 beats/min just after the injection of a local anesthesia containing adrenaline. A few minutes later, the HR decreased and the LBBB disappeared. While the patient was awakening from the general anesthesia, the HR increased to 83 beats/min and the LBBB re-appeared. Seven hours after the general anesthesia, the LBBB disappeared ; however, inverted T waves were observed in the precordial leads.
In the present case, the CLBBB was transient and was accompanied by an increase in the HR. This kind of transient LBBB is reportedly called rate-dependent LBBB. In addition, the inverted T waves observed in the precordial leads in the present case were not a symptom of myocardial ischemia, but rather an example of a previously reported phenomenon known as cardiac memory.
Even if an underlying cardiovascular disease does not exist, CLBBB sometimes causes a delayed contraction of the left ventricle and a subsequent decrease in the left ventricular ejection fraction, followed by the circulation insufficiency, during general anesthesia. The appropriate management of circulatory dynamics, such as avoiding tachycardia, should be carefully performed perioperatively.
