Mild hypothermia attenuates ischemia/reperfusion injury - insights from serial non-invasive pressure-volume loops

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BACKGROUND: Mild hypothermia, 32-35°C, reduces infarct size in experimental studies, potentially mediating reperfusion injuries, but human trials have been ambiguous. To elucidate the cardioprotective mechanisms of mild hypothermia, we analyzed cardiac performance in a porcine model of ischemia/reperfusion, with serial cardiovascular magnetic resonance (CMR) imaging throughout one week using non-invasive pressure-volume loops.

METHODS AND RESULTS: Normothermia and Hypothermia groups sessions (n=7+7 pigs, nonrandom allocation) were imaged with CMR at baseline and subjected to 40 minutes of normothermic ischemia by catheter intervention. Thereafter, the Hypothermia group was rapidly cooled (mean 34.5°C) for 5 minutes before reperfusion. Additional CMR sessions at two hours, 24 hours, and seven days acquired ventricular volumes and ischemic injuries (unblinded analysis).Stroke volume (-24%; p=0.029; Friedmans test) and ejection fraction (-20%; p=0.068) were notably reduced at 24h in the Normothermia group compared to baseline. In contrast, the decreases were ameliorated in the Hypothermia group (stroke volume: -6%; p=0.77; ejection fraction: -6%; p=0.13). Mean arterial pressure remained stable in Normothermic animals (-3%, p=0.77) but dropped two hours post-reperfusion in hypothermic animals (-18%, p=0.007). Both groups experienced a decrease and partial recovery pattern for PV loop-derived variables over one week, but the adverse effects tended attenuated in the Hypothermia group. Infarct sizes were 10±8% in Hypothermic and 15±8% in Normothermic animals (p=0.32). Analysis of covariance at 24 hours indicated that hypothermia has cardioprotective properties incremental to reducing infarct size, such as higher external power (p=0.061) and lower arterial elastance (p=0.015).

CONCLUSION: Using non-invasive pressure-volume loops by CMR, we observed that mild hypothermia at reperfusion alleviates the heart's work after ischemia/reperfusion injuries during the first week and preserves short-term cardiac performance. This hypothesis-generating study suggests hypothermia to have cardioprotective properties, incremental to reducing infarct size. The primary cardioprotective mechanism was likely an afterload reduction acutely unloading the left ventricle.

Original languageEnglish
Article numbercvad028
JournalCardiovascular Research
Publication statusE-pub ahead of print - 2023 Feb 3

Bibliographical note

© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.

Subject classification (UKÄ)

  • Cardiac and Cardiovascular Systems


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