Electromechanical characterization of myocardial hibernation in a pig model

Background. This study attempted to assess in-vivo electromechanical changes following gradual coronary artery occlusion in a pig ameroid constrictor model using a novel three-dimensional left ventricular mapping system. Methods and results. We measured unipolar and bipolar voltage potentials and local endocardial shortening in the ischemic lateral and non-ischemic anterior zones in animals at rest (n = 9) 5 weeks after the implantation of ameroid constrictors around the left circumflex artery. Echocardiography was used to assess regional contractility (percentage myocardial thickening), and an echo-contrast perfusion study was performed using acoustic densitometry methods. The ischemic lateral zone showed reduced myocardial perfusion at rest (peak intensity; 3.4 ± 1.7 versus 20.7 ± 14.8, P = 0.005), impaired mechanical function (percentage wall thickening 22 ± 19% versus 40 ± 11%, P = 0.03; local endocardial shortening 2.9 ± 5.5% versus 11.7 ± 2.1%, P = 0.002), and preserved electrical activity (unipolar voltage 12.4 ± 4.7 versus 14.4 ± 1.9 mV, P = 0.25; bipolar voltage 4.1 ± 1.1 versus 3.8 ± 1.5 mV, P = 0.62), compared with the anterior region. Conclusions. Gradual coronary artery occlusion resulting in regional reduced perfusion and function at rest (i.e. hibernating myocardium) is characterized by preserved electrical activity. An electromechanical left ventricular mapping procedure such as the one described here may be of diagnostic value for identifying the hibernating myocardium.