Clinical Studies
Detection of myocardial injury during transvenous implantation of automatic cardioverter-defibrillators

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Abstract

OBJECTIVES

The present study was designed to assess the extent of myocardial injury in patients undergoing transvenous implantation of an automatic implantable cardioverter-defibrillator (ICD) using cardiac troponin I (cTNI), which is a highly specific marker of structural cardiac injury.

BACKGROUND

During ICD implantation, repetitive induction and termination of ventricular fibrillation (VF) via endocardial direct current shocks is required to demonstrate the correct function of the device. Transthoracic electrical shocks can cause myocardial cell injury.

METHODS

Measurements of total creatine kinase (CK), CK-MB, myoglobin, cardiac troponin T (cTNT) and cTNI were obtained before and after ICD implantation in 49 consecutive patients. Blood samples were drawn before and 2, 4, 8, and 24 h after implantation.

RESULTS

Elevations of CK, CK-MB, myoglobin, cTNT and cTNI above cut-off level were found in 25%, 6%, 76%, 37% and 14% of patients, respectively, with peak cTNI concentrations ranging from 1.7 to 5.5 ng/ml. Cumulative defibrillation energy (DFE), mean DFE, cumulative VF time, number of shocks as well as prior myocardial infarction (MI) were found to be significantly related to a rise of cTNI. Mean DFE ≥ 18 J and a recent MI were identified as strong risk factors for cTNI rise.

CONCLUSIONS

During transvenous ICD implantation myocardial injury as assessed by cTNI rise occurs in about 14% of the patients. Peak cTNI concentrations are only minimally elevated reflecting subtle myocardial cell damage. Patients with a recent MI and a mean DFE ≥ 18 J seem to be prone to cTNI rise.

Abbreviations

CAD
coronary artery disease
CK
creatine kinase
cTNI
cardiac troponin I
cTNT
cardiac troponin T
DFE
defibrillation energy
DFT
defibrillation threshold
ICD
implantable cardioverter-defibrillator
LVEF
left ventricular ejection fraction
MI
myocardial infarction
VT/VF
ventricular tachycardia/ventricular fibrillation

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