Early detection of ischemia by implantable cardioverter defibrillator capable of intracardiac electrogram monitoring in a case of old myocardial infarction.

A 72-year-old man received an implantation of implantable cardioverter defibrillator with intracardiac electrogram (ICEG) monitoring because ventricular fibrillation occurred in a case of old myocardial infarction with reduced left ventricular function. A year later, he came to our hospital for a regular checkup. Unexpectedly, ST depression was recorded by ICEG monitoring. He had no significant symptoms at the time, but had had exertional chest discomfort about 3 or 4 weeks before. The patient subsequently underwent successful revascularization, which potentially prevented the recurrence of acute myocardial infarction. ST depression has not been recorded by ICEG monitoring since the revascularization.