Introduction: During therapeutic hypothermia, QT interval is prolonged. Therapeutic hypothermia can be a useful test to unmask latent long QT syndrome (LQTs).
Case: A 23-year-old man resuscitated from cardiac arrest was referred to out hospital. AED detected and terminated VF. On admission, his 12-lead ECG showed that QT interval was within normal limit (QT/QTc: 370/440ms). His serum potassium (4.5mEq/L) was within normal limit. He remained in comatose after his hemodynamic status had stabilized. He underwent therapeutic hypothermia. During therapeutic hypothermia, his QT interval markedly prolonged (QT/QTc: 720/600ms). Electrolyte abnormalities were checked frequently and corrected immediately. No arrhythmic event was occurred during therapeutic hypothermia. After completion of rewarming, QT interval was normalized. He was fully recovered without any neurologic damage. A cardiac echocardiogram showed no structural heart disease and normal left ventricular function. A coronary angiography showed no significant stenosis. During epinephrine infusion test, QT interval was markedly prolonged (QT/QTc: 480/640ms). He was diagnosed with latent LQTs. After placement of ICD, his was discharged from our hospital.
Conclusions: Therapeutic hypothermia can be a powerful test to unmask latent LQTs.