QTc prolongation during therapeutic hypothermia: are we giving it the attention it deserves?
OBJECTIVE
Therapeutic hypothermia (TH) is used in neuroprotection following cardiac arrest due to ventricular tachycardia (VT) and ventricular fibrillation (VF). Accidental hypothermia is itself known to cause prolongation of the corrected QT interval (QTc). QTc prolongation can cause polymorphic VT and VF. If this also occurs in TH, it may induce refibrillation. We investigated the effect of TH on the QTc interval.


RESULTS
Prospective case series of all patients undergoing TH following cardiac arrest following VT/VF at our hospital between July 2008 and January 2009. We studied the effect of temperature on QTc. All electrocardiograms (ECGs) undertaken during TH were studied and compared with the ECG prior to this. Four patients underwent TH. A total of 10 ECGs were undertaken during TH. The QTc was normal prior to TH. It became prolonged (>460 ms) in all cases during TH and normalized after cessation of TH, apart from Patient 4 who did not have an ECG post-TH since she died from cardiogenic shock. There was a negative correlation between temperature and QTc (Pearson's correlation coefficient, r= -0.71).


CONCLUSIONS
Our series illustrates QTc prolongation during TH. This carries potential for refibrillation. Guidelines on ECG monitoring during TH are needed, especially since hypothermic myocardium is intrinsically prone to arrhythmias and commonly used antiarrythmic drugs such as amiodarone can prolong the QTc.
Khan
Jamal Nasir
JN
Sandwell and City Hospitals NHS Trust, Bham B18 7QH, UK. mally777@hotmail.com
Prasad
Neeraj
N
Glancy
James Michael
JM
D000368:Aged; D001831:Body Temperature / Q000502:physiology; D002118:Calcium / Q000097:blood; D004562:Electrocardiography; D005260:Female; D017408:Guidelines as Topic; D006323:Heart Arrest / Q000209:etiology / Q000628:therapy; D006801:Humans; D007036:Hypothermia, Induced / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011188:Potassium / Q000097:blood; D011446:Prospective Studies; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000150:complications / Q000209:etiology*; D014693:Ventricular Fibrillation / Q000150:complications / Q000209:etiology*
D011188:Potassium; D002118:Calcium