Endo- and epicardial mapping of spontaneous ventricular fibrillation during acute myocardial infarction in a porcine model

Abstract

Abstract Introduction Ventricular fibrillation (VF) during the first minutes of acute myocardial infarction (AMI) is among the most frequent causes of sudden cardiac death. Albeit mechanisms for arrhythmogenesis during ischemia are well understood on a cellular level, little is known in an in-vivo setting. Aim Aim of this study was the development and characterization of a porcine model of AMI and spontaneous VF with continuous electrical mapping using a non-contact mapping system (EnSite Array) in the left ventricle (LV) and an electrode sock covering the whole heart. Activation-recovery intervals (ARI), beat-to-beat variation in repolarization (BVR), and ectopic activation were measured. Methods Nineteen Danish Landrace pigs (56±4 kg, heart weight 251±20 g) were anaesthetized, equipped with electrophysiological (EP) catheters in the coronary sinus, right and LV as well as a multi electrode array (St. Jude, EnSite Array) catheter in the LV. Thoracotomy was performed and the sock electrode was placed on the pericardium covering the anterior and the posterior surface of the heart. Finally, the mid-left anterior descendent artery was occluded with a percutaneous transluminal coronary angioplasty balloon to induce AMI and kept in place for 45 minutes followed by 20 minutes of reperfusion. Data from both systems were analyzed offline using a custom-made software. Results All pigs had stable hemodynamic parameters during the procedure. Spontaneous VF occurred in 8/19 pigs during the occlusion period. Epi- and endocardial mapping showed similar shortening of ARI in the infarcted area (Figure 1A). AMI shortened ARI in the ischemic area to a greater extend in pigs that developed VF (Figure 1B) and caused beat-to-beat variation in repolarization (BVR) in later phases (Figure 1C). Ectopic beats proceeding spontaneous VF varied in activation site and subsequent repolarization (Figure 1D, left). Multiple short-coupled ectopic beats destabilized the electrical substrate further and led to progressive ARI shortening (Figure 1D, last 4 beats). Conclusion We present the first whole heart mapping experiments of spontaneous VF during AMI with endo- and epicardial mapping. Pigs with VF had shorter ARI, greater dispersion but similar BVR during AMI compared to those without VF. These findings provide a deeper understanding of arrhythmogenesis during AMI and can help to develop new antiarrhythmic drugs or to assess risk factors of VF. Funding Acknowledgement Type of funding sources: None.