Although cardiac troponin, has been demonstrated to be elevated in some patients with implantable cardioverter defibrillators(ICDs) who receive spontaneous or induced electrical shocks, the significance of these elevations remains unclear. The purpose of this study was to investigate the potential clinical significance of Troponin-T (TnT) elevation in patients who have suffered ICD discharges.
A retrospective analysis of 257 ICD charts identified 23 patients who experienced a total of 30 arrhythmic events that prompted ICD discharges, after which at least one measurement of serum troponin T had been performed within 24 hours.
An elevated level of TnT was found in 11 episodes (36%): 13 episodes had been treated with 1 shock, 3 with 2 shocks, and 14 required 3 or more shocks. Arrhythmic events occurred in 7 patients without coronary artery disease (CAD), 19 in patients with CAD withoutacute coronary syndrome (ACS), and 4 in patients with ACS. The characteristics of the three groups are presented below.
No CADCAD without ACSACSpAge (yrs)56 ± 1074 ± 875 ± 100.0002No. shocks/episode3 ± 3.63 ± 1.766.5 ± 8.5NSTotal energy delivered/ episode (J)20 ± 754 ± 41100 ± 1320.086Patients with positive TnT1(14%)7(36%)3(75%)0.141Peak TnT (ng/ml)0.04 ± 0.050.07 ± 0.060.29 ± 0.260.011Peak TnT values were significantly lower during the events that occurred in patients without CAD than in patients with CAD with or without ACS. Only one of the patients without CAD had abnormal TnT(>0.10 ng/ml). The abnormal TnT levels that occurred after ICD shocks were all in the 0.1-0.2ng/dl range, excepting two patients with ACS. There was a weak positive correlation between peak TnT levels and the number of shocks, and total energy delivered per arrhythmia episode (but without statistical significance).CONCLUSIONS: TnT release does not occur in the majority of spontaneous ICD discharges, even in patients with underlying CAD; TnT elevations after ICD shocks should not be assumed to be caused solely by the electric discharges. A TnT between 0.1 and 0.2 ng/ml should prompt further evaluation to rule out an acute coronary event.
It seems reasonable to check TnT levels in all patients with CAD who suffer ICD discharges because this could lead to identification of underlying ischemic events.
D. Blendea, None.