Raised Troponins And Survival With ICD

Cardiac troponin T (cTnT) elevations have been reported to occur after implantable cardioverter-defibrillator (ICD) discharges, but their prognostic significance is unknown. Now US investigators have evaluated whether cTnT elevations occurring after ICD discharges have an impact on survival.

Cardiac troponin T (cTnT) or troponin I release has been reported to occur after spontaneous or induced ICD discharges in some, but not all patients. The mechanism for such troponin release has not yet been clearly elucidated. The potential prognostic significance of this phenomenon has not been studied. Troponin elevation after ICD discharge might reflect myocardial damage from the discharge itself, coronary ischaemia that precipitated the triggering arrhythmia, underlying “fragility” of myocardial cell metabolism or some combination of these factors. Troponin elevation in serum has been reported to be associated with adverse outcome in diverse populations, including survivors of non-ST-elevation, myocardial infarction, those with renal failure or heart failure, patients undergoing percutaneous or surgical revascularisation, and even in a community-based cohort of 70-year old men. A further study among ICD recipients, showed that a raised troponin level before ICD implant was an independent marker for increased mortality. These investigators did not examine troponin release after ICD discharges.

Given these considerations, the aims of this study were first, to determine the characteristics of patients who have cTnT release after ICD discharge and second, to examine the potential relationship between such release and survival.

In the current prospective observational study, 174 patients (mean (SD) aged 68 (12 years), 32 women) who received spontaneous (n = 66) or induced (n = 108) ICD discharges were studied. The mean (SD) left ventricular ejection fraction was 29 (11)%.

Troponin T was measured between 12 and 24h after ICD discharge. Patients received between 1 and 19 discharges (mean (SD) 2.4 (2.4)), with total delivered energy ranging from 6 to 288 J (mean (SD) 41 (63) J. The relationship between cTnT levels and all-cause mortality was assessed in univariate and multivariate analyses.

Results showed that during a median follow-up period of 41.8 months (range 3 – 123), 56 patients died. Patients with a post-discharge cTnT level of ≥0.05 ng/ml had worse survival than those with cTnT <0.05 ng/ml. The significant relationship between raised cTnT and survival was retained in Cox multivariate analysis adjusted for total ICD energy delivered during an arrhythmia episode, age, sex, presence of coronary artery disease, left ventricular ejection fraction and serum creatinine.

Elevation of troponin T after ICD discharge, even when it occurs after device testing, is a risk factor for mortality that is independent of other common clinical factors that predict survival in such patients.

Reference:

Troponin T elevation after implanted defibrillator discharge predicts survival. Blendea D, Blendea M, Banker J, McPherson C A. Heart 2009 95: 1153 – 1158.