Automatic implantable cardioverter/defibrillator discharges and acute myocardial injury.

Multiple defibrillations by the automatic implantable cardioverter/defibrillator (AICD) have been reported to result in localized epicardial damage. No data exist, however, regarding whether this damage can be detected in the clinical setting or whether it interferes with the detection of true myocardial infarction. Forty-nine patients who received defibrillations by patch electrodes were studied prospectively. We attempted to document the presence of myocardial injury with the following three commonly used modalities for the detection of myocardial infarction: serial electrocardiographic changes, serial creatine phosphokinase (CPK) and CPK-MB release, and technetium 99m pyrophosphate scanning. Fifteen patients received defibrillations by AICD patches at the time of AICD generator replacement. Nine patients received defibrillations at the time of new AICD lead placement. The average total energy delivered was 85 +/- 29 J. None of these patients had detectable myocardial injury. Ten patients had defibrillations by the AICD patches at the time of bypass operation. One patient in this group developed acute myocardial infarction in the inferior wall after posterior descending coronary bypass operation, as detected by electrocardiogram, 99mTc pyrophosphate scanning, and CPK-MB analysis. Fifteen patients were evaluated for spontaneous AICD discharges. Thirteen had a maximum of five consecutive shocks, and cumulative energy delivered was not greater than 330 J. None of these patients had detectable injury. Two patients had CPK-MB release of 15.3% and 7.5%, respectively. One of these patients had a positive 99mTc pyrophosphate scan. These two patients received 12 and 17 rapid and consecutive AICD discharges, respectively, with cumulative delivered energy of 360 and 510 J, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)