Is there value in testing troponin levels after ICD discharge?

May 10, 2013

February 26, 2014

Dr Chris Targett, Specialty Doctor in Emergency Medicine (Hinchingbrooke Hospital NHS Trust Emergency Department)

Prof Tim Harris , Hinchingbrooke Hospital NHS Trust Emergency Department

In [an adult patient whose ICD has discharged] is [a rise in troponin] suggestive of [an ischaemic cardiac event precipitating ICD discharge or defibrillation induced myocyte damage]?

A 50-year-old man presents to the emergency department having been woken from sleep by his implanted cardioverter-defibrillator (ICD) firing; it has fired twice more since that time. He is in sinus rhythm and has no acute signs or symptoms. A recent angiogram showed no significant coronary artery disease (CAD). You speak to the Cardiology Registrar who advises that troponin levels should be checked. You wonder if there is any evidence for this and, further, how you might interpret the result.

Ovid MEDLINE(R) 1946 to November Week 3 2013: ((defibrillators.af. AND implantable.af.) OR exp Defibrillators, Implantable/ OR implantable defibrillator$.af.) AND troponin.af. OR exp Troponin/ Results limited to English language and studies in humans.

The Cochrane Library Issue 12 of 12 December 2013: MeSH descriptor: [Troponin] explode all trees AND ICD:ti,ab,kw (Word variations have been searched) OR MeSH descriptor: [Pacemaker, Artificial] explode all trees

Google Scholar December 2013: >8000 search results.

Ovid search retrieved 38 papers of which 11 were relevant. PubMed clinical queries: No additional papers identified. Cochrane search retrieved three papers, none of which were relevant. Two additional papers of note identified from first 100 best matches in Google Scholar. No paper directly answered the question posed. The relevant papers are summarised in the following table

The majority of papers deal with defibrillator threshold testing (DFT) rather than spontaneous discharge, and use a variety of troponin assays. From the above research it can be seen that myocyte damage from an ICD discharge alone can raise troponin levels, and the more shocks, the higher the rise. There is no proven difference in level of troponin rise due to whether the discharge was appropriate, inappropriate or from DFT, but a positive troponin level is more common in spontaneous discharges. A small but significant proportion of patients whose ICD discharges on a background of CAD will have acute coronary syndrome (ACS). There is limited data in these studies to suggest that likely non-ACS related rises tend to peak earlier than those from ACS which confirms expert clinical experience that myocardial ischaemia causes a more prolonged troponin release compared to the discrete insult of an ICD discharge for arrhythmia.

Interrogation of any recently discharged ICD should be requested on all patients. Whether to employ a troponin level test depends on the patient's history of CAD and the clinical evaluation of ACS. Any patient with a confirmed absence of CAD (all patients with ICD will have had imaging of their coronary arteries) and who presents without symptoms of ACS does not require troponin level evaluation. So in the clinical scenario, the patient could be considered for discharge once ICD interrogation has been arranged. Any patient symptomatic of ACS should be managed as per local ACS protocol with a troponin assay. Any patient with known CAD but without symptoms of ACS should be discussed promptly with an electrophysiologist or, if this is not possible, have a 6–12 h troponin assay (depending on local policy). If the troponin assay is negative, the patient can be considered for discharge once ICD interrogation has been arranged. If the troponin assay is positive, the patient should be managed as per local ACS protocol.

The number of implanted cardioverter defibrillator (ICD) discharges must be taken into account when evaluating any troponin level rise. Overall, a positive troponin assay post-ICD discharge is independently associated with an increased mortality.

1. Davoodi G, Mohammadi V, Shafiee A et al.. Detection of myocardial injury due to defibrillation threshold checking after insertion of implantable cardioverter/defibrillators.
2. Toh N, Nishii N, Nakamura K et al.. Cardiac dysfunction and prolonged hemodynamic deterioration after implantable cardioverter-defibrillator shock in patients with systolic heart failure.
3. Francis CK, Kuo YH, Azzam I et al.. Brain natriuretic peptide and biomarkers of myocardial ischemia increase after defibrillation threshold testing.
4. Bhavnani SP, Kluger J, Coleman CI et al.. The prognostic impact of shocks for clinical and induced arrhythmias on morbidity and mortality among patients with implantable cardioverter-defibrillators.
5. Blendea D, Blendea M, Banker J et al.. Troponin T elevation after implanted defibrillator discharge predicts survival.
6. Alaiti MA, Maroo A, Edel TB. Troponin levels after cardiac electrophysiology procedures: review of the literature.
7. Daubert JP, Zareba W, Cannom DS et al.. Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.
8. Hasdemir C, Shah N, Rao AP et al.. Analysis of troponin I levels after spontaneous implantable cardioverter defibrillator shocks.
9. Poole JE, Johnson GW, Hellkamp AS et al.. Prognostic importance of defibrillator shocks in patients with heart failure.
10. Schlüter T, Baum H, Plewan A et al.. Effects of implantable cardioverter defibrillator implantation and shock application on biochemical markers of myocardial damage.
11. Rao SP, Miller S, Rosenbaum R et al.. Cardiac troponin I and cardiac enzymes after electrophysiologic studies, ablations, and defibrillator implantations.
12. Hurst TM, Hinrichs M, Breidenbach C et al.. Detection of myocardial injury during transvenous implantation of automatic cardioverter-defibrillators.
13. Joglar JA, Kessler DJ, Welch PJ et al.. Effects of repeated electrical defibrillations on cardiac troponin I levels.