Effects of Implantable Cardioverter Defibrillator Implantation and Shock Application on Biochemical Markers of Myocardial Damage

Abstract

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, repetitive induction and termination of ventricular fibrillation by direct current shocks is required. This may lead to minor myocardial damage. Cardiac troponin T (cTnT) and I (cTnI) are specific markers for the detection of myocardial injury. Because these proteins usually are undetectable in healthy individuals, they are excellent markers for detecting minimal myocardial damage. The objective of this study was to evaluate the effect of defibrillation 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 intraoperative shock application. Results: Depending on the effectiveness of shocks and the energy applied, the cardiac-specific markers cTnT and cTnI, as well as CK-MB mass, showed a significant increase compared with the baseline value before testing and peaked for the most part 4 h after shock application. In contrast, the increases 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 cardiac markers into the circulation. This release seems to be of cytoplasmic origin and depends on the number and effectiveness of the shocks applied.

The Ischemia‐Modified Albumin in Relation to Pacemaker and Defibrillator Implantation

“…Indeed, patients with left ventricular dysfunction had higher baseline IMA values compared to those with preserved systolic function; this may be one of the reasons that IMA changes are blunted in the ICD group versus the PPM group, the other reason being the fact that PPM patients are on paced rhythm after the completion of the procedure with subsequent altered depolarization and possibly subendocardial ischemia whereas ICD patients are usually on their intrinsic rhythm. Minimally elevated troponin concentrations, reflecting minor myocardial injury, have also been described following transvenous ICD implantation, [20][21][22] but this has been mainly attributed to the induction and termination of VF episodes during testing. However, the only study that included a control group with similar threshold testing and generator replacement but without electrode insertion, did not find a detectable increase in troponin whereas it did show a modest but significant increase in its levels following transvenous ICD implantation.…”

The Dilemma of ICD Implant Testing

“…In patients with coronary artery disease, hypotension due to prolonged episodes of VF may result in myocardial ischemia. Perioperative myocardial infarction is difficult to diagnose because routine defibrillation testing 190 shocks delivered for spontaneous VT/VF or supraventricular tachycardia may cause both elevation of troponin 191 and non-specific ECG changes. However, in an analysis of shocks for spontaneous arrhythmias, tro-ponin elevations were both more likely and higher in patients with coronary artery disease than in those without, 192 suggesting that the combination of VT/VF and shocks causes ischemic injury in some patients.…”

Termination of Ventricular Tachycardia by Far‐Field Stimulation in Humans: A Feasibility Study

“…The myocardial damage induced by defibrillation shocks seems to be related to the shock energy delivered. [3][4][5][6][7] The 100 V/0.12-ms field stimulus contains only 0.1% of the energy of a ≥20-J high-energy shock. Therefore, a therapy strategy for VT including field stimuli after failed ATP before the delivery of high-energy shocks may be less damaging to the heart 3-7 than the direct application of a high-energy shock after failed ATP.…”

“…High-energy shocks from implantable cardioverter-defibrillators (ICDs) reliably terminate any kind of ventricular tachyarrhythmia. 1,2 There have been many attempts to reduce unnecessary shocks, mainly because of the pain they cause and battery consumption, but also because of reports of myocardial damage [3][4][5][6][7] after ICD shocks. The relevance of this last aspect has been highlighted by a recent study that suggested that paradoxically, although they are lifesaving, appropriate ICD shocks for ventricular arrhythmia increase mortality, probably by influencing heart-failure mechanisms.…”