Myocardial stunning: a temperature dependent phenomenon.
Two recently completed studies in our laboratory have evaluated the relationship between myocardial temperature during cardioplegic preservation and calcium accumulation within the cell. In the large animal model, the pig, we investigated the influence of normothermic versus hypothermic blood cardioplegic preservation on sarcoplasmic reticulum calcium ATPase activity and calcium uptake following 2-hour cardioplegic arrest and 1 hour of normothermic reperfusion. The second investigation in the small animal model, the rat, measured intracellular calcium concentration in hearts subjected to cardioplegic arrest by continuous administration of cardioplegia at temperatures from 4 degrees to 37 degrees C. In the pig heart, global left ventricular function and coronary blood flow were improved, while creatine kinase release was reduced in the warm preserved heart. The rate of sarcoplasmic reticulum calcium uptake and calcium ATPase activity were impaired only in the presence of hypothermic preservation, and the higher calcium ATPase activity corresponded to the higher rate of sarcoplasmic reticulum calcium uptake observed in the warm preserved heart. Measurements of intracellular calcium concentration accomplished with a spectrofluorimeter documented a significant increase in free calcium in the 4 degrees C and 20 degrees C preserved rat heart during normothermic reperfusion. At both 28 degrees and 37 degrees C preservation, the free calcium level did not increase. It is concluded that intracellular calcium accumulation is associated with hypothermic preservation. Hypothermia appears to jeopardize the control of calcium homeostasis, which then is manifested as a more rapid increase of intracellular calcium during reperfusion. This would be associated with increased myocardial stunning in the hypothermic heart.(ABSTRACT TRUNCATED AT 250 WORDS)
Engelman
R M
RM
Department of Surgery, Baystate Medical Center, Springfield, MA 01107.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004195:Disease Models, Animal; D006321:Heart / Q000502:physiology*; D006324:Heart Arrest, Induced; D009204:Myocardial Revascularization; D017682:Myocardial Stunning / Q000503:physiopathology*; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013552:Swine; D013696:Temperature
D002118:Calcium