• Heart Rhythm · Jan 2019

    Multicenter Study

    Dynamicity of hypothermia-induced J waves and the mechanism involved.

    • Yoshifusa Aizawa, Yukio Hosaka, Hirotaka Oda, Koichi Fuse, Masaaki Okabe, Yoshiaki Kaneko, Naohiko Takahashi, Hirofumi Zaizen, Yoshiyasu Aizawa, and Keiichi Fukuda.
    • Research and Development, Tachikawa Medical Center/Niigata University, Nagaoka/Niigata, Japan. Electronic address: aizaways@med.niigata-u.ac.jp.
    • Heart Rhythm. 2019 Jan 1; 16 (1): 74-80.

    BackgroundJ waves develop during hypothermia, but the dynamicity of hypothermia-induced J waves is poorly understood.ObjectiveThe purpose of this study was to investigate the mechanism of the rate-dependent change in the amplitude of hypothermia-induced J waves.MethodsNineteen patients with severe hypothermia were included (mean age 70 ± 12 years; 16 men [84.2%]). The rectal temperature at the time of admission was 27.8° ± 2.5°C. In addition to prolonged PR, QRS complex, and corrected QT intervals, the distribution of prominent J waves was widespread in all 19 patients.ResultsNine patients showed changes in RR intervals. When the RR interval shortened from 1353 ± 472 to 740 ± 391 ms (P = .0002), the J-wave amplitude increased from 0.50 ± 0.29 to 0.61 ±0.27 mV (P = .0075). The J-wave amplitude increased in 7 patients (77.8%) and decreased in 2 patients (22.2%) after short RR intervals. The augmentation of J waves at short RR intervals was associated with a significant prolongation of ventricular activation time (35 ± 5 ms vs 46 ± 5 ms; P = .0020), suggesting accentuated conduction delay. Increased conduction delay at short RR intervals was suggested to accentuate the phase 1 notch of the action potential and J waves in hypothermia. None developed ventricular fibrillation, and in 2 of 9 patients with atrial fibrillation, atrial fibrillation persisted after rewarming to normothermia.ConclusionJ waves in severe hypothermia were augmented after short RR intervals in 7 patients as expected for depolarization abnormality, whereas 2 patients showed a bradycardia-dependent augmentation as expected for transient outward current-mediated J waves. Increased conduction delay at short RR intervals can be responsible for the accentuation of the transient outward current and J waves during severe hypothermia.Copyright © 2018 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

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