The Effect of Therapeutic Hypothermia on the QT Interval in Postcardiac Arrest Cases

Postcardiac arrest (PCA) syndrome is associated with high cardiovascular morbidity and mortality. Prolongation of the QT interval can lead to life-threatening ventricular arrhythmias and sudden cardiac death. Therapeutic hypothermia (TH) is widely used to improve neurological outcomes in PCA patients, but its effects on the QT interval remain a subject of investigation. This study aimed to evaluate the impact of TH on corrected QT (QTc) intervals in PCA patients. A total of 48 patients (mean age 63.2 ± 11.3 years) who survived cardiac arrest and underwent TH were included. Standard 12-lead electrocardiograms (ECGs) and serum electrolyte levels were assessed before and after TH. The QT and QTc intervals were measured using Bazett's formula, and QT dispersion (QTd) was calculated as the difference between the maximum and minimum QT intervals. Following TH, a significant increase in RR intervals was observed (480.75 ± 91.75 ms vs. 660.43 ± 97.35 ms, p < 0.05). QTc intervals increased significantly from 397.13 ± 12.45 ms to 449.25 ± 21.40 ms (p < 0.05). Similarly, QTd increased from 55.48 ± 12.45 ms to 67.41 ± 13.42 ms (p < 0.05). The prolongation of the QT interval was associated with a significant decrease in serum potassium and calcium levels. In conclusion, TH leads to a significant prolongation of the QT and QTc intervals and an increase in QTd. These findings suggest that close ECG monitoring is essential in PCA patients undergoing TH, particularly in those with predisposing factors for arrhythmias.