Key result
Mild hypothermia increases LV pressure ~32% vs normothermia in isolated rabbit hearts at low rates.
Why the study?
The effects of mild hypothermia on cardiac contractility at varying heart rates in isolated rabbit hearts were not fully understood.
Does mild hypothermia combined with varying heart rates affect global myocardial contraction in isolated rabbit hearts?
Population
Isolated rabbit hearts perfused with Krebs-Henseleit solution paced after atrioventricular block
Comparison
Mild hypothermia (30 degrees C) vs normothermia (37 degrees C) at varying pacing rates with or without isoproterenol
Design
Preclinical experimental study using Langendorff technique
Authors
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Mild hypothermia effects in isolated hearts should not yet inform clinical practice; leaves open translation to in vivo or human settings.
Does mild hypothermia combined with varying heart rates affect global myocardial contraction in isolated rabbit hearts?
Effect estimate: 32% increase
Absolute Event Rate: 146.5% vs 110.7%
Mild hypothermia exerts a positive inotropic effect at low heart rates but causes diastolic dysfunction and reduced contractility at higher heart rates in isolated rabbit hearts, which can be partially reversed by isoproterenol.
Mattheussen et al. (1996) studied this question. Mild hypothermia vs. Normothermia (37 degrees C) was evaluated on Isovolumetric left ventricular pressure (LVP) at low heart rates (< 30 bpm) (32% increase). In isolated rabbit hearts at low heart rates (<30 bpm), mild hypothermia (30°C) increased left ventricular pressure by 32% compared to normothermia (146.5 vs 110.7 mm Hg).
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