title: Electrocardiographic changes during induced therapeutic hypothermia in comatose survivors after cardiac arrest.
abstract: OBJECTIVE
  To assess the safety of therapeutic hypothermia (TH) concerning arrhythmias we analyzed serial electrocardiograms (ECG) during TH.
  
  
  METHODS
  All patients recovered from a cardiac arrest with Glasgow < 9 at admission were treated with induced mild TH to 32-34 °C. TH was obtained with cool fluid infusion or a specific intravascular device. Twelve-lead ECG before, during, and after TH, as well as ECG telemetry data was recorded in all patients. From a total of 54 patients admitted with cardiac arrest during the study period, 47 patients had the 3 ECG and telemetry data available. ECG analysis was blinded and performed with manual caliper by two independent cardiologists from blinded copies of original ECG, recorded at 25 mm/s and 10 mm/mV. Coronary care unit staff analyzed ECG telemetry for rhythm disturbances. Variables measured in ECG were rhythm, RR, PR, QT and corrected QT (QTc by Bazett formula, measured in lead v2) intervals, QRS duration, presence of Osborn's J wave and U wave, as well as ST segment displacement and T wave amplitude in leads II, v2 and v5.
  
  
  RESULTS
  Heart rate went down an average of 19 bpm during hypothermia and increased again 16 bpm with rewarming (P < 0.0005, both). There was a non-significant prolongation of the PR interval during TH and a significant decrease with rewarming (P = 0.041). QRS duration significantly prolonged (P = 0.041) with TH and shortened back (P < 0.005) with rewarming. QTc interval presented a mean prolongation of 58 ms (P < 0.005) during TH and a significant shortening with rewarming of 22.2 ms (P = 0.017). Osborn or J wave was found in 21.3% of the patients. New arrhythmias occurred in 38.3% of the patients. Most frequent arrhythmia was non-sustained ventricular tachycardia (19.1%), followed by severe bradycardia or paced rhythm (10.6%), accelerated nodal rhythm (8.5%) and atrial fibrillation (6.4%). No life threatening arrhythmias (sustained ventricular tachycardia, polymorphic ventricular tachycardia or ventricular fibrillation) occurred during TH.
  
  
  CONCLUSIONS
  A 38.3% of patients had cardiac arrhythmias during TH but without life-threatening arrhythmias. A concern may rise when inducing TH to patients with long QT syndrome.
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Salinas
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Esteban
authors.initials: E
authors.lastname: Lopez-de-Sa
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Pena-Conde
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Viana-Tejedor
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Juan Ramon
authors.initials: JR
authors.lastname: Rey-Blas
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Armada
authors.affiliation: Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain.
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Lopez-Sendon
keywords: Cardiac arrest; Cardiac arrythmias; Post-cardiac arrest síndrome; QT interval; Therapeutic hypothermia