Electrophysiologic substrate and intraventricular left ventricular dyssynchrony in nonischemic heart failure patients undergoing cardiac resynchronization therapy

Abstract

Background Electrocardiographic Imaging (ECGI) is a method for noninvasive epicardial EP mapping. ECGI was used previously to characterize the electrophysiological substrate and electrical synchrony in a very heterogeneous group of patients with varying degrees of coronary disease and ischemic cardiomyopathy. Objective The objective of this study is to characterize the LV electrophysiological substrate and electrical dyssynchrony using ECGI, in a homogeneous group of non-ischemic cardiomyopathy patients who were previously implanted with CRT device. Methods ECGI was performed in different rhythms in 25 patients by programming their devices to biventricular pacing, single chamber (LV or RV) pacing, and native rhythm. Electrical dyssynchrony index (ED) was computed as the standard deviation of activation times at 500 sites on LV epicardium. Results In all patients, native rhythm activation was characterized by lines of conduction block in a region with steep activation – recovery interval (ARI) gradients between the epicardial aspect of septum and LV lateral wall. A native QRS duration (QRSd)> 130 ms was associated with high ED (≥30 ms) while QRSd <130 ms was associated with minimal (25 ms) to large (40 ms) ED. CRT responders had very high dyssynchrony (ED=35.5±3.9 ms) in native rhythm which was significantly lowered (ED=23.2±4.4 ms) during CRT. All four non-responders in the study did not show significant difference in ED between native and CRT rhythms. Conclusions The electrophysiological substrate in non-ischemic cardiomyopathy is consistent among all patients, with steep ARI gradients co-localizing with conduction block lines between the epicardial aspect of the septum and the LV lateral wall. A QRSd wider than 130 ms is indicative of substantial LV electrical dyssynchrony, while among patients with QRSd<130 ms LV dyssynchrony may vary widely.

Maximal Electric Separation–Guided Placement of Right Ventricular Lead Improves Responders in Cardiac Resynchronization Defibrillator Therapy

“…28,29 In this study, the subgroup analysis demonstrated benefit in both causes, with a trend toward a higher number of responders in the dilated cardiomyopathy group (Table 6). …”

Analysis of Ventricular Activation Using Surface Electrocardiography to Predict Left Ventricular Reverse Volumetric Remodeling During Cardiac Resynchronization Therapy

“…A close linkage between electric and mechanical asynchrony has been demonstrated in animal models 11 and preliminarily in humans. 12 The greater the LV conduction delay, the greater are the potential gains in reverse remodeling when conduction delay is sufficiently corrected, if it is assumed that LV scar volume is not prohibitive. Targeting LV pacing sites with the use of real-time ECGs to evaluate evidence of activation wavefront fusion and reversal, rather than rigid adherence to anatomic targets, may improve CRT response.…”

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

“…A key advantage of this technique is the ability to non-invasively identify the area of LEA, and this approach has already been shown to allow peri-procedural guidance of the LV lead to the target site. ECGI can also compute an LV electrical dyssynchrony index, and this metric appears may predict patients likely to respond to CRT and aid in identifying the optimal site during LV lead deployment [108,109]. …”