Quantitative indices of dispersion of refractoriness for identification of propensity to re-entrant ventricular tachycardia in a canine model of myocardial infarction

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Abstract
Study objective – To identify propensity to re-entry in a canine model of 7 day old myocardial infarction, the sensitivity and specificity of five indices of dispersion of refractoriness (ERP) were investigated. Design – With an epicardial patch electrode containing 47 electrodes, ERP was measured by S1-S2 method at each site overlying the infarct, ERP range, maximum adjacent dispersion, difference between mean ERPS of the infarct and normal zones, standard deviation (σ) of the mean ERP, and σ/mean ERP × 100 were calculated. Experimental material – 42 dogs were divided into three groups; 20 dogs with epicardial functional block on induction of sustained ventricular tachycardia or fibrillation, 10 dogs with inducible ventricular tachycardia or fibrillation but without epicardial functional block, and 12 control dogs without ventricular tachycardia, fibrillation or block. Measurements and main results – All five indices were significantly greater in the 20 dogs with ventricular tachycardia or fibrillation than in control dogs. A receiver operating characteristic curve analysis of the five indices showed that σ was the most sensitive and specific index for discriminating these 20 dogs. The sensitivity and specificity of a σ value greater than 14 ms (the mean value plus two SD of the control dogs) were 70% and 100%, respectively. Conclusions – The σ of the mean ERP at multiple sites could serve as a quantitative index for determining ERP dispersion.

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