Release of high-sensitive TROPonin T by implantation of an entirely subcutaneous Implantable Cardioverter-defibrillator compared to a conventional transvenous approach: the TROPIC registry.

Purpose: Implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD) has become an alternative option when a conventional transvenous approach is not suitable. The myocardial damage caused by S-ICD implantation appears to be minimal despite mandatory defibrillation threshold (DFT) testing. However, there has not been a direct comparison with the traditional transvenous placement of a single-chamber ICD (VVI-ICD). The aim of this study was to determine the extent of myocardial damage by analysing the changes in serum levels of cardiac enzymes after S-ICD implantation in comparison with VVI-ICD.
Methods: In 43 patients who received an S-ICD system, differences in serum levels of high-sensitive troponin T (ΔhsTnT) and creatine kinase total (ΔCK) and muscle brain fraction (ΔCK-MB) were acquired by blood sampling before and the day after implantation. The control group consisted of 43 patients from the TropShock study who had received a transvenous VVI-ICD without DFT.
Results: After S-ICD implantation and testing procedure, ΔhsTnT (0.000 ng/ml, IQR - 0.003-0.002 ng/ml) was significantly lower than after conventional VVI-ICD implantation (0.018 ng/ml, IQR 0.004-0.032 ng/ml; p < 0.001). There was no significant difference in CK (ΔCK _S-ICD 85.0 U/I, IQR 30.5-225.8 U/I vs ΔCK _VVI-ICD 69.5 U/I, IQR 22.9-172.3 U/I; p = 0.357), but there was a significant difference in CK-MB (ΔCK-MB _S-ICD of - 0.60, IQR - 2.60-1.0 vs ΔCK-MB _VVI-ICD 1.0, IQR - 1.08-3.18; p = 0.030).
Conclusion: S-ICD implantation causes less myocardial damage than VVI-ICD implantation evidenced by ΔhsTnT and ΔCK-MB.
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