Effects of implantable cardioverter defibrillator implantation and shock application on biochemical markers of myocardial damage

Background: Implantable cardioverter defibrillator (ICD) implantation is a common approach in patients at high risk of sudden cardiac death. To check for normal function, it is necessary to test the ICD. For this purpose, rep etitive induction and termination of ventricular fibrillation by direct cur rent shocks is required. This may lead to minor myocardial damage. Cardiac troponin T (cTnT) and I (cTnI) are specific markers for the detection of my ocardial injury. Because these proteins usually are undetectable in healthy individuals, they are excellent markers for detecting minimal myocardial d amage. The objective of this study was to evaluate the effect of defibrilla tion of induced ventricular fibrillation on markers of myocardial damage. Methods: This study included 14 patients who underwent ICD implantation and intraoperative testing. We measured cTnT, cTnI, creatine kinase MB (CK-MB) mass, CK activity, and myoglobin before and at definite times after intrao perative shock application. Results: Depending on the effectiveness of shocks and the energy applied, t he cardiac-specific markers cTnT and cTnI, as well as CK-MB mass, showed a significant increase compared with the baseline value before testing and pe aked for the most part 4 h after shock application. In contrast, the increa ses in Ck activity and myoglobin were predominantly detectable in patients who received additional external shocks. Conclusions.. ICD implantation and testing leads to a short release of card iac markers into the circulation. This release seems to be of cytoplasmic o rigin and depends on the number and effectiveness of the shocks applied. (C ) 2001 American Association for Clinical Chemistry.