• Raed Abu Sham'a, Pablo Nery, Mouhannad Sadek, Derek Yung, Calum Redpath, Mark Perrin, Bradley Sarak, and David Birnie.
• Division of Cardiology, Department of Medicine, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
• Pacing Clin Electrophysiol. 2014 Feb 1; 37 (2): 237-41.

BackgroundPatients who receive appropriate implantable cardioverter defibrillator (ICD) shocks have a subsequent adverse prognosis. Most data suggest that patients with inappropriate ICD shocks also have a subsequent adverse prognosis, although this is more controversial. The shocks may be an epiphenomenon, that is, a marker of underlying disease progression; however, it cannot be excluded that shocks cause direct myocardial damage. This latter question is difficult to clarify as the arrhythmia provoking the shock can also cause troponin release. Inappropriate shocks secondary to lead fracture are an ideal situation to examine this question; any troponin release in an otherwise well and hemodynamically stable patient, is likely due directly to the shocks.MethodsAll patients with Fidelis lead fracture admitted to our institution with inappropriate shocks were included in this study. Troponin (I or T) was considered positive if the level was above the 99th percentile reference cutoff.ResultsElevated troponin levels were recorded in 16 of 22 patients (73%). Patients with elevated troponin received a higher number of shocks (20.3 ± 30.1 vs 5.3 ± 4.8, P = 0.07) compared with patients with normal troponin. Very elevated troponin levels (>0.8 mcg/L) were seen in five of 22 (22%) patients. The mean peak troponin level for these five patients was 7.06 ± 8.56 mcg/L; two patients had troponin levels that would be expected from a medium-sized myocardial infarction or severe myocarditis.ConclusionTroponin elevation occurred in the majority of our patients after inappropriate ICD discharges secondary to lead fracture. This indicates that ICD shocks can cause myocardial injury.©2013, The Authors. Journal compilation ©2013 Wiley Periodicals, Inc.

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