Repolarization and ventricular arrhythmia during targeted temperature management post cardiac arrest.

BACKGROUND: Targeted temperature management (TTM) following out-of-hospital cardiac arrest (OHCA) prolongs the QT-interval but our knowledge of different temperatures and risk of arrhythmia is incomplete.

OBJECTIVE: To assess whether the QTc, QT-peak (QTp) and T-peak to T-end interval (TpTe) may be useful markers of ventricular arrhythmia in contemporary post cardiac arrest treatment.

METHODS: An ECG-substudy of the TTM-trial (TTM at 33°C vs. 36°C) with serial ECGs from 680 (94%) patients. Bazett's (B) and Fridericia's (F) formula were used for heart rate correction of the QT, QTp and TpTe. Ventricular arrhythmia (VT/VF) were registered during the first three days of post cardiac arrest care.

RESULTS: The QT, QTc and QTp intervals were prolonged more at 33°C compared to 36°C and restored to similar and lower levels after rewarming. The TpTe-interval remained between 92-100 ms throughout TTM in both groups. The QTc intervals were associated with ventricular arrhythmia, but not after adjustment for cardiac arrest characteristics. The QTp-interval was not associated with risk of ventricular arrhythmia. Heart rate corrected TpTe-intervals were associated with higher risk of arrhythmia (Odds ratio (OR): TpTe(B): 1.12 (1.02-1.23, p=0.01 TpTe(F): 1.12 (1.02-1.23, p=0.02) per 20 ms). Further a prolonged TpTe-interval ≥90 ms was consistently associated with higher risk (ORadjusted : TpTe(B): 2.05 (1.25-3.37), p<0.01, TpTe(F): 2.14 (1.32-3.49), p<0.01).

CONCLUSIONS: TTM prolongs the QT-interval by prolongation of the QTp-interval without association to increased risk. The TpTe-interval is not significantly affected by core temperature, but heart rate corrected TpTe intervals are robustly associated with risk of ventricular arrhythmia. Trial Registration The TTM-trial is registered and accessible at ClinicalTrials.gov (Identifier: NCT01020916).