Observational Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Cardiol. Jul 26, 2015; 7(7): 423-430
Published online Jul 26, 2015. doi: 10.4330/wjc.v7.i7.423
Electrocardiographic changes during induced therapeutic hypothermia in comatose survivors after cardiac arrest
Pablo Salinas, Esteban Lopez-de-Sa, Laura Pena-Conde, Ana Viana-Tejedor, Juan Ramon Rey-Blas, Eduardo Armada, Jose Luis Lopez-Sendon
Pablo Salinas, Ana Viana-Tejedor, Instituto Cardiovascular, Hospital Clínico San Carlos, 28040 Madrid, Spain
Esteban Lopez-de-Sa, Laura Pena-Conde, Juan Ramon Rey-Blas, Eduardo Armada, Jose Luis Lopez-Sendon, Acute Cardiac Care Unit, Division of Cardiology, Hospital Universitario La Paz, 28046 Madrid, Spain
Author contributions: All the authors contributed to this manuscript.
Institutional review board statement: The institutional ethics review committee approved the retrospective anonymous analysis of the patients, in accordance with European guidelines for good clinical practice.
Informed consent statement: All patient’s relatives signed informed consents for the clinical procedures performed during admission. No special tests were done for the realization of this study, nor there was any follow-up. Therefore, no specific informed consent was obtained for this the retrospective anonymous observational study.
Conflict-of-interest statement: The authors declear no conflicts of interest.
Data sharing statement: Technical appendix, statistical code, and dataset available from the corresponding author at estebanlopezdesa@secardiologia.es. Consent was not obtained but the presented data are anonymized and risk of identification is very low or absent.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Esteban Lopez-de-Sa, MD, FESC, Head, Acute Cardiac Care Unit, Division of Cardiology, Hospital Universitario La Paz, Paseo de la Castellana 261, 28046 Madrid, Spain. estebanlopezdesa@secardiologia.es
Telephone: +34-917-277199 Fax: +34-917-277135
Received: February 7, 2015
Peer-review started: February 8, 2015
First decision: March 6, 2015
Revised: May 3, 2015
Accepted: May 5, 2015
Article in press: May 6, 2015
Published online: July 26, 2015
Processing time: 178 Days and 11.2 Hours
Abstract

AIM: 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.

CONCLUSION: 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.

Keywords: Cardiac arrest; Therapeutic hypothermia; Post-cardiac arrest síndrome; Cardiac arrythmias; QT interval

Core tip: Induced, therapeutic hypothermia is a treatment for post-cardiac arrest syndrome with a potential survival benefit; however it is not widely used. We aimed to assess the safety of this therapy regarding cardiac arrhythmias through a systematical evaluation of electrocardiograms (ECG) changes during hypothermia and telemetry data. Our conclusions are that therapeutic hypothermia according to current practice is safe with arrhythmias in one third of the patients (38.3%) but no life-threatening arrhythmias. Bradycardia and reversible prolongation of ECG intervals are common findings. A concern may rise when inducing hypothermia to patients with arrhythmias related to long QT syndrome.