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Systolic and diastolic left ventricular dysfunction due to mild hypothermia.
P S Greene1, D E Cameron, M L Mohlala
1Division of Cardiac Surgery, Johns Hopkins Medical Institutions, Baltimore, MD 21205.
Circulation
|November 1, 1989
Summary
Mild hypothermia significantly impairs left ventricular (LV) contractility and diastolic function in cardiac patients. This study demonstrates reduced regional work and prolonged relaxation times even at mild hypothermic temperatures.
Area of Science:
- Cardiovascular Physiology
- Cardiac Surgery
Background:
- Postoperative cardiac patients often experience mild hypothermia.
- The impact of mild hypothermia on left ventricular (LV) contractility is not well understood.
Purpose of the Study:
- To investigate the effects of mild hypothermia on LV contractility and diastolic function.
- To quantify changes in regional work and pressure decay during varying temperatures.
Main Methods:
- Six pigs underwent partial right ventricular bypass with controlled heart rate.
- Myocardial temperature was manipulated between 34°C and 38°C.
- LV regional work and isovolumic relaxation time constants were measured using sonomicrometer crystals.
Main Results:
- Regional work decreased significantly from 85.1% at 38°C to 31.9% at 34°C.
- LV pressure decay time constants prolonged from 44.8 ms to 61.6 ms as temperature decreased.
- These findings indicate a marked depression of LV contractility and diastolic function.
Conclusions:
- Mild hypothermia, even at levels encountered clinically post-cardiac surgery, markedly depresses LV contractility.
- Hypothermia negatively impacts both systolic and diastolic function of the left ventricle.