Mild hypothermia induces incomplete left ventricular relaxation despite spontaneous bradycardia in pigs

Aim Mild hypothermia (MH) decreases left ventricular (LV) end‐diastolic capacitance. We sought to clarify whether this results from incomplete relaxation. Methods Ten anaesthetized pigs were cooled from normothermia (NT, 38 °C) to MH (33 °C). LV end‐diastolic pressure (LVPed), volume (LVVed) and pre...

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Bibliographic Details
Published in:Acta Physiologica 2015-03, Vol.213 (3), p.653-663
Main Authors: Schwarzl, M., Alogna, A., Zirngast, B., Steendijk, P., Verderber, J., Zweiker, D., Huber, S., Maechler, H., Pieske, B. M., Post, H.
Format: Article
Language:English
Subjects:
Animals
Blood pressure
Bradycardia
Bradycardia - diagnosis
Bradycardia - etiology
Bradycardia - physiopathology
Capacitance
Cardiac Pacing, Artificial
Cardiology
Diastole
Heart Rate
Hypothermia
Hypothermia, Induced - adverse effects
left ventricular compliance
left ventricular relaxation
mild hypothermia
pressure-volume analysis
Stroke Volume
Swine
Time Factors
Ventricle
Ventricular Dysfunction, Left - diagnosis
Ventricular Dysfunction, Left - etiology
Ventricular Dysfunction, Left - physiopathology
Ventricular Function, Left
Ventricular Pressure
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Summary:Aim Mild hypothermia (MH) decreases left ventricular (LV) end‐diastolic capacitance. We sought to clarify whether this results from incomplete relaxation. Methods Ten anaesthetized pigs were cooled from normothermia (NT, 38 °C) to MH (33 °C). LV end‐diastolic pressure (LVPed), volume (LVVed) and pressure–volume relationships (EDPVRs) were determined during stepwise right atrial pacing. LV capacitance (i.e. LVVed at LVPed of 10 mmHg, LV VPed10) was derived from the EDPVR. Pacing‐induced changes of diastolic indices (LVPed, LVVed and LV VPed10) were analysed as a function of (i) heart rate and (ii) the ratio between diastolic time interval (t‐dia) and LV isovolumic relaxation constant τ, which was calculated using a logistic fit (τL) and monoexponential fit with zero asymptote (τZ) and nonzero asymptote (τNZ). Results Mild hypothermia decreased heart rate (85 ± 4 to 68 ± 3 bpm), increased τL (22 ± 1 to 57 ± 4 ms), τZ (26 ± 2 to 56 ± 5 ms) and τNZ (41 ± 1 to 96 ± 5 ms), decreased t‐dia/τ ratios, and shifted the EDPVR leftwards compared to NT (all P 
ISSN:1748-1708
1748-1716
DOI:10.1111/apha.12439