Multisize electrodes for substrate identification in ischemic cardiomyopathy validation by integration of whole heart histology

Abstract

OBJECTIVES This study sought to evaluate the value of combined electrogram (EGM) information provided by simultaneous mapping using micro- and conventional electrodes in the identification of post-myocardial infarction ventricular tachycardia substrate.BACKGROUND Ventricular tachycardias after myocardial infarction are related to scars with complex geometry. Scar delineation and ventricular tachycardia substrate identification relies on bipolar voltages (BV) and EGM characteristics. Early reperfusion therapy results in small, nontransmurat scars, the details of which may not be delineated using 3.5 mm tip catheters.METHODS Nine swine with early reperfusion myocardial infarction were mapped using Biosense Webster's QDOT Micro catheter, incorporating 3 microelectrodes at the tip of the standard 3.5 mm electrode. Analysis of EGM during sinus rhythm, right ventricular pacing, and short-coupled right ventricular extrastimuli was performed. The swine were sacrificed and mapping data were projected onto the heart. Transmural biopsies (n 196) corresponding to mapping points were obtained, allowing a head-to-head comparison of EGM recorded by micro- and conventional electrodes with histology.RESULTS To identify scar areas using standard electrodes, unique cutoff values of unipolar voltage <5.44 mV, BV <1.27 my (conventional), and BV <2.84 mV (microelectrode) were identified. Combining the information provided by unipolar voltage and BV mapping, the sensitivity of scar identification was increased to 93%. Micro-EGM were better able to distinguish small near-fields corresponding to a layer of viable subendocardium than conventional EGM were.CONCLUSIONS The combined information provided by multisize electrode mapping increases the sensitivity with which areas of scar are identified. EGM from microetectrodes, with narrower spacing, allow identification of near-fields arising from thin subendocardiat layer and layers activated with short delay obscured in EGM from conventional mapping catheter. (C) 2019 by the American College of Cardiology Foundation.