Andrew D. Beaser

Entrainment of ventricular tachycardia: Is the pacing site in or out?

A 77-year-old man with a history of ischemic cardiomyopathy with an ejection fraction of 35%was referred for ablation of recurrent ventricular tachycardia (VT). Electroanatomic mapping of the epicardium revealed apical scar during right ventricular pacing, with focal activation during VT, originating from the apex. Endocardial mapping confirmed the extensive dense scar extending from the base toward the apex along the anteroseptal wall. Within the more apical portion of the scar, there was a localized region with late potentials and split electrograms. The clinical VTwas induced by endocardial pacingwithin the anteroseptal scar and was hemodynamically tolerated. Overdrive pacing was performed to assess the response to entrainment with a multielectrode catheter that recorded local diastolic activity (Figure 1). Is the pacing site in or out of the reentrant circuit?

Impact of high-grade atrioventricular block and cumulative frequent pacing on atrial arrhythmias

The relationship between high‐grade atrioventricular block (HGAVB) with cumulative frequent pacing and risk of atrial arrhythmias (AAs) has not been well characterized. We hypothesized HGAVB and pacing may have significant impact on incidence and prevalence of AAs by modulating atrial substrate.

Electroanatomic Characterization of a “No Access” Hypoplastic Left Ventricle

A 35-year-old man with congenital mitral atresia, a double outlet right ventricle with a hypoplastic left ventricle (HLV), and post-bidirectional Glenn and Fontan status was referred for ablation of symptomatic premature ventricular contractions (PVCs) and nonsustained ventricular tachycardia. He

Law of Spatial Averaging During Endocardial Voltage Mapping: You Can’t Trim Out the Fat!

See Article by Samanta et al Since the introduction and widespread application of 3-dimensional electroanatomic mapping, voltage-based displays of the arrhythmogenic substrate have greatly facilitated the practice of scar-related ventricular tachycardia (VT) ablation. The detection of scar is predicated on a voltage threshold (<1.5 mV) used to differentiate scar from normal tissue.1 However, there has been a resurgence of interest in the fundamental principles of bipolar and unipolar voltage recordings that complicate our oversimplistic classification of low voltage on a binary system, scar or normal.2 Bipolar and unipolar amplitudes are influenced by the orientation of the recording electrode relative to the activation wavefront, which exhibits anisotropic conduction properties relative to fiber orientation and fibrosis. Recordings are necessarily made with instruments or tools, and the size, shape, and spacing of an electrode pair determine the amount of myocardium sampled by the virtual electrode.3 Voltage recordings represent an electrical biopsy, and the electrogram amplitude represents a spatial average of the relative proportion of myocardial mass to fibrosis in a given sample.4 This explains why a higher voltage threshold may be warranted to detect fibrosis in patients with hypertrophic cardiomyopathy. The number of viable myocytes that comprise an electrogram with a clinical recording tool remains unknown at present. The field of view may be much larger than the region of interest. The significance of the law of spatial averaging can be appreciated by imagining a bipolar recording with the distal electrode in contact with transmural scar and the proximal electrode in contact with normal myocardium. The resulting voltage does not reflect the exact information from either electrode. Consistent with this consideration, we …