Elsevier

Heart Rhythm

Volume 19, Issue 2, February 2022, Pages 187-194
Heart Rhythm

Clinical
Ventricular Tachycardia
Sinus rhythm QRS amplitude and fractionation in patients with nonischemic cardiomyopathy to identify ventricular tachycardia substrate and location

https://doi.org/10.1016/j.hrthm.2021.09.028Get rights and content

Background

Ventricular tachycardia (VT) substrate in left ventricular (LV) nonischemic cardiomyopathy (NICM) consists of fibrosis with surviving myocardium.

Objective

The purpose of this study was to determine whether, in patients with LV NICM and sustained VT, reduced QRS amplitude and QRSf during sinus rhythm can identify the presence and location of abnormal septal (S-NICM) and/or free-wall (FW-NICM) VT substrate.

Methods

We compared patients with NICM and VT (group 1) with electroanatomic mapping septal (S-NICM; n = 21) or free-wall (FW-NICM; n = 20) VT substrate to a 38-patient reference cohort (group 2) with cardiac magnetic resonance imaging (cMRI) and NICM but no VT referred for primary prevention implantable cardioverter-defibrillator (26 [68.4%] with late gadolinium enhancement).

Results

Group 1 had lower QRS amplitude in leads II (0.60 ± 0.22 vs 0.86 ± 0.35, P <.001), aVR (0.60 ± 0.24 vs 0.75 ± 0.31, P = .002), aVF (0.48 ± 0.20 vs 0.70 ± 0.28, P <.001), and V2 (1.09 ± 0.52 vs 1.38 ± 0.55, P = .001) than group 2. QRS <0.55 mV in lead aVF identified VT and accompanying substrate with sensitivity 70% and specificity 71%. Most group 1 and group 2 patients had 12-lead ECG QRS fractionation (QRSf) in ≥2 contiguous leads (78% vs 63.2%, P = .14). Sensitivity and specificity for ≥2 QRSf leads identifying respective regional electroanatomic or cMRI abnormalities were 76% and 50% for inferior, 44% and 87% for lateral, and 21% and 89% for anterior leads.

Conclusion

In LV NICM, low frontal plane QRS (<0.55 mV in aVF) is associated with VT substrate. Although multilead QRS fractionation is associated with the presence and location of VT substrate, it is frequently identified in patients without VT with cMRI abnormalities.

Introduction

The arrhythmogenic substrate in left ventricular (LV) nonischemic cardiomyopathy (NICM) usually consists of fibrosis interspersed with surviving myocardium.1, 2, 3, 4 The majority of patients with LV NICM and ventricular tachycardia (VT) have a perivalvular substrate that is predominantly septal (S-NICM) or free wall (FW-NICM).5 In patients with S-NICM VT substrate, fibrosis commonly affects the basal midmyocardium and endocardium (ENDO) extending to the anteroseptum, inferoseptum, periaortic LV, aortic cusps, aortic mitral continuity, and right ventricular (RV) septum.6 In contrast, patients with FW-NICM VT substrate have a high prevalence of epicardial (EPI) substrate, and although typically with a basal lateral location, the substrate can extend to or primarily involve the inferior and anterior LV free wall.3,4,7

We hypothesized that the fibrotic process associated with the VT substrate may be reflected on the 12-lead electrocardiogram (ECG) as reduced QRS amplitude and multilead QRS fractionation (QRSf) during sinus or other supraventricular rhythm.4,8,9 The aim of this study was to determine whether, in patients with LV NICM and sustained VT, reduced QRS amplitude and QRSf during sinus rhythm can identify the presence and location of abnormal S-NICM and/or FW-NICM VT substrate.

Section snippets

Study population

We included between February 2019 and November 2020 a prospective cohort of 41 patients with NICM and monomorphic sustained VT (group 1). Patients had an identifiable VT substrate on electroanatomic mapping (EAM), either S-NICM or FW-NICM, and evidence of VT circuit(s) based on activation, entrainment, and/or pacemapping in those distinct regions. VT substrate was defined by the presence of low-voltage, long-duration, fractionated electrograms, split signals, and/or isolated late potentials on

Study cohort characteristics: Group 1

A total of 41 patients met the prospective cohort inclusion criteria with NICM, sustained VT, and defined electroanatomic substrate. Twenty-one (51%) were categorized as having predominant S-NICM (Supplemental Figure 2) and 20 (49%) predominant FW-NICM substrate (Figure 2). Patients with S-NICM and FW-NICM substrate were similar in terms of gender, number of antiarrhythmic drugs attempted before ablation, and LV ejection fraction. However, patients with FW-NICM substrate had a higher prevalence

Discussion

This study of patients with NICM documents the value of QRS amplitude and fractionation as markers of electroanatomic and LGE defined scar and manifest VT. The main findings of our investigation are as follows. (1) Group 1 patients with electroanatomic substrate and manifest VT showed lower QRS amplitude in all leads compared to group 2 patients with prophylactic ICD and no manifest VT with or without LGE. (2) QRS amplitude <0.55 mV in aVF identified with moderate sensitivity (70%) and

Conclusion

In patients with LV NICM, low QRS amplitude in aVF (<0.55 mV) and V6 (<0.96 mV) can help to identify and localize VT substrate. Although multilead QRSf is associated with the presence and likely location of electroanatomic or LGE scar and therefore may provide some benefit in regionalization, it is not specific for VT substrate and is frequently identified in patients without VT.

References (21)

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Cited by (3)

Funding Sources: This work was supported by the Richard T. and Angela Clark Innovation Fund in Cardiovascular Medicine, the Mark S. Marchlinski EP Research and Education Fund, and the Winkelman Family Fund in Cardiovascular Innovation.

Disclosures: Dr Marchlinski has served as a consultant for Abbott Medical, Biosense Webster, Biotronik, and Medtronic Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

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