Use of myocardial electrical impedance to assess the efficacy of preconditioning

Myocardial electrical impedance (MEI) has been found to correlate with ischemia and ischemic preconditioning (PC). In this study, the short-term effects of adenosine preconditioning on the MEI were studied in a swine model of beating heart coronary revascularization. Juvenile farm pigs were assigned to have either no PC (CTRL) or adenosine PC (ADO), receiving subsequently two ischemia/reperfusion (IR) insults. In both groups, MEI increased immediately with induced ischemia. However, its progression to ischemic plateau after reaching a maximum rate of change took significantly longer for ADO animals (7.13/spl plusmn/1.03 min) than for the CTRL (4.56/spl plusmn/0.16 min) (P<0.05). Such period of time was defined as a time constant. MEI was able to distinguish between study groups by evaluating the time required to reach ischemic plateau and from its rate of change (first derivate).