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THE JOURNAL OF CARDIOVASCULAR SURGERY
Rivista di Chirurgia Cardiaca, Vascolare e Toracica
Indexed/Abstracted in: BIOSIS Previews, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
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ORIGINAL ARTICLES CARDIAC PAPERS
The Journal of Cardiovascular Surgery 1999 August;40(4):481-6
Effects of heat stress on metabolism of high-energy phosphates. Comparison of normothermic and hypothermic ischemia
Jayakumar J., Smolenski R. T., Gray C. C., Goodein A. T., Amrani M., Yacoub M. H.
From the Department of Cardiothoracic Surgery National Heart and Lung Institute Imperial College School of Medicine Harefield Hospital, Harefield, Middlesex, UK
Background. Alterations in metabolic pathways may contribute to the cardioprotective effects of heat stress (HS). We investigated the effects of HS on ATP and phosphocreatine (PCr) levels in the ischemic rat myocardium, after both normothermic and hypothermic ischemia.
Methods. Two protocols were used: (1) normothermic ischemia (20 min at 37°C) with no myocardial protection (n=6 HS; n=6 control); (2) hypothermic ischemia (4 hrs at 4°C) after cardioplegic arrest (n=6 HS; n=6 control). ATP and PCr levels in the heart were measured using 31P nuclear magnetic resonance spectroscopy.
Results. At the end of normothermic ischemia, ATP levels were better maintained in HS hearts (C vs HS: 4.51±0.66 vs 7.81±1.06 μmol/g dry wt±SEM, p=0.04). A trend for higher ATP content in HS hearts was observed after 40 min of reperfusion (C vs HS: 11.7±1.5 vs 16.9±2.0 μmol/g dry wt±SEM, p=0.09). PCr content was also higher at the end of 40 minutes of reperfusion in HS hearts (C vs HS: 46.4±2.9 vs 56.9±3.0 μmol/g dry wt±SEM, p=0.03). After prolonged hypothermic ischemia under cardioplegic arrest, heat stress again led to better preservation of ATP levels at the end of ischemia (C vs HS: 5.71±0.88 vs 9.23±1.38 μmol/g dry wt±SEM, p=0.05) and after 40 minutes of reperfusion (C vs HS: 16.8±1.4 vs 24.6±2.8 μmol/g dry wt±SEM, p=0.03). PCr levels were also better maintained at the end of ischemia (C vs HS: 4.87±0.77 vs 12.4±3.0 μmol/g dry wt±SEM, p=0.03) and after 40 minutes of reperfusion in HS hearts (C vs HS: 55.1±7.0 vs 79.8±7.3 μmol/g dry wt±SEM, p=0.03).
Conclusions. Heat stress induces changes in the energy profile of the heart which results in better preservation of ATP and phosphocreatine levels. These changes could be observed after brief normothermic ischemia and also after prolonged hypothermic ischemia under cardioplegic arrest, mimicking conditions of preservation for cardiac transplantation.