Background: Cardiac troponin is routinely tested in the post-cardiac arrest setting, but its utility in identifying ischemic etiology and predicting left ventricular systolic dysfunction (LVSD) and survival is not known.
Methods: In a single-center registry, 145 consecutive patients who achieved return of spontaneous circulation after cardiac arrest underwent serial troponin T (TnT) testing, echocardiogram, and expert adjudication of etiology. Initial and peak TnT were evaluated for assessing ischemic etiology, LVSD, and survival to discharge using area under the receiver operating characteristic curve (AUROC).
Results: The mean age of patients was 61 ± 14y and 72% were men. Of the 145 arrests, 19% had an ischemic etiology, 68% had LVSD post arrest, and 55% survived to discharge. Median initial TnT was 0.4 ng/ml (IQR 0.1 - 4.1) and peak was 5.8 ng/ml (IQR 0.7 - 32.5). Compared to a non-ischemic etiology, an ischemic etiology was associated with a 4-fold higher initial (median [IQR] 0.24 [0.04-1.9] vs 0.9 [0.2-9.0]) and an 8-fold higher peak (1.5 [0.3-23.7] vs 12.6 [2.2-43.8]) TnT (p < .01). Further, compared to patients without LVSD, those with LVSD had a 6-fold higher initial (0.2 [0.04-1.4] vs 1.2 [0.2-6.1]) and a 9-fold higher peak (1.3 [0.2-12.6] vs 11.6 [1.3-43.8]) TnT (p <.01). Survivors and non-survivors had similar TnT levels. All patients had a positive TnT at 0.1 ng/ml (clinical cut-off). Even at higher cut-offs - 10x, 100x and 1000x, initial TnT performed poorly (AUROC 0.57, 0.56, and 0.56) and peak TnT performed modestly (AUROC 0.55, 0.61, and 0.62) as diagnostic tests for ischemic etiology. Similarly, even at higher cut-offs, initial (AUROC 0.60, 0.62, 0.55) and peak (AUROC 0.57, 0.61, and 0.62) TnT performed poorly to modestly at predicting LVSD. The test performed poorly for predicting survival to discharge (AUROC for all <0.6).
Conclusions: Patients with an ischemic cardiac arrest, and those developing LVSD post-arrest had higher initial and peak TnT levels. However, both at current as well as several-fold higher thresholds for a positive test, TnT does not perform sufficiently well to guide clinical decision-making or predict patient outcomes. Therefore, the strategy of its routine testing in a post-cardiac arrest setting should be reevaluated.