Scar Homogenization Versus Limited-Substrate Ablation in Patients With Nonischemic Cardiomyopathy and Ventricular Tachycardia

Authors, Journal, Affiliations, Type, DOI

• Authors: Yalçın Gökoglan, Sanghamitra Mohanty, Carola Gianni, Pasquale Santangeli, Chintan Trivedi, Mahmut F. Güneş, Rong Bai, Amin Al-Ahmad, G. Joseph Gallinghouse, Rodney Horton, Patrick M. Hranitzky, Javier E. Sanchez, Salwa Beheiry, Richard Hongo, Dhanunjaya Lakkireddy, Madhu Reddy, Robert A. Schweikert, Antonio Dello Russo, Michela Casella, Claudio Tondo, J. David Burkhardt, Sakis Themistoclakis, Luigi Di Biase, Andrea Natale
• Journal: Journal of the American College of Cardiology 2016;68(18):1990–1998
• Affiliations: Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas, and collaborating centres in the United States, Italy and Turkey
• Type: Prospective, single-centre, non-randomised comparative cohort
• DOI: 10.1016/j.jacc.2016.08.033

Overview

This study tested whether endo-epicardial scar homogenization improves long-term ventricular arrhythmia (VA)-free survival compared with standard limited-substrate ablation in non-ischaemic dilated cardiomyopathy (NICM). Ninety-three consecutive patients with NICM (LVEF <40%, no significant coronary disease), monomorphic scar-related VT, an ICD, and bipolar voltage <1.5 mV on electroanatomic mapping were allocated by operator preference to standard ablation (n=57) or endo-epicardial homogenization of all abnormal potentials within the scar (n=36). Acute non-inducibility of any VT was higher with homogenization (69.4% vs 42.1%, p=0.01). Over a mean 14±2 months, freedom from any VA after a single procedure was 63.9% versus 38.6% (log-rank p=0.031), and rehospitalisation was lower (8.3% vs 26.3%, p=0.035). The authors conclude that homogenization is a reasonable initial strategy in NICM with demonstrable scar, but that success remains below that achieved in ischaemic cardiomyopathy because septal and midmyocardial scar is often inaccessible.

Keywords

Non-ischaemic cardiomyopathy; ventricular tachycardia; catheter ablation; scar homogenization; epicardial ablation; low-voltage areas

Key Takeaways

Design and population

• Prospective study of 108 screened consecutive patients; 93 included (57 standard, 36 homogenization), 16 excluded for absence of endocardial or epicardial scar by standard bipolar cut-offs.
• NICM defined as LVEF <40% without significant coronary artery disease; all patients had an ICD and monomorphic scar-related VT.
• Allocation was by operator preference, not randomisation.
• Groups were similar except for lower LVEF in the homogenization group (29±5% vs 32±6%, p=0.028).
• Epicardial mapping was performed in all 36 homogenization patients (100%) and 30 of 57 standard patients (52.6%) — the latter when VT remained inducible after endocardial ablation or no endocardial scar was found.

Procedural strategy

• Standard ablation: substrate mapping plus activation/entrainment and pace mapping, with RF during VT until termination and local electrogram abatement or loss of capture.
• Homogenization: detailed substrate mapping of all abnormal electrograms within the scar, then empirical ablation throughout the entire endocardial scar; epicardial scar was ablated if it contained at least three abnormal electrograms.
• "Normal" electrograms were defined as ≤3 sharp deflections, amplitude >1.5 mV, duration <70 ms (and/or amplitude/duration ratio >0.046).
• Ablation used an open irrigated 3.5-mm catheter, up to 50 W, 40°C limit.
• Acute endpoint: non-inducibility of any monomorphic VT, excluding non-clinical VTs with cycle length <200 ms, polymorphic VT and VF, tested with two drive cycle lengths, three extrastimuli, two sites, with and without isoproterenol.

Procedural outcomes

• Non-inducibility of any VT: 25/36 (69.4%) with homogenization vs 24/57 (42.1%) with standard ablation (p=0.01).
• Non-inducibility of the clinical VT: 77.8% vs 63.2% (p=0.138) — not significantly different.
• RF time was longer with homogenization (43.6±37.6 vs 21.2±13.4 min, p<0.001); fluoroscopy time also longer (28.8±11.5 vs 21.3±11.1 min, p=0.003).
• Cardiopulmonary support was required in 7 standard-ablation patients and none in the homogenization group (p=0.041).
• Procedural complications occurred in 2/36 (5.6%) vs 12/57 (21%) (p=0.042), driven mainly by femoral access complications in patients requiring mechanical support and by transient renal dysfunction.

Long-term outcomes

• Mean follow-up 14±2 months.
• Freedom from any VA after a single procedure: 23/36 (63.9%) vs 22/57 (38.6%), log-rank p=0.031; 48.4% of the whole cohort.
• Rehospitalisation for VT or heart failure: 3/36 (8.3%) vs 15/57 (26.3%) (p=0.035).
• Atrial fibrillation occurred in 14/93 (15%) during follow-up.
• Among the 13 homogenization-group recurrences, 9 (69.2%) had incomplete substrate elimination because the scar was septal/midmyocardial (n=6) or perivalvular near the mitral annulus with overlying fat or coronary arteries (n=3).

Predictors of recurrence

• Univariate predictors: low LVEF (p<0.001), male sex (p=0.043), acute procedural failure (p<0.001), standard ablation (p=0.032).
• Multivariate: homogenization HR 0.48 (95% CI 0.27–0.96; p=0.027) and LVEF HR 0.93 per percentage point (95% CI 0.91–0.98; p=0.008).
• Non-inducibility of any VT at the end of the procedure did not predict long-term success in this cohort.
• The authors compare 64% freedom from VA after homogenization in NICM with 81% after the same strategy in ischaemic cardiomyopathy in their earlier work.

Interpretation

• The benefit is attributed to elimination of "innocent islets" of surviving myocardium that can sustain undocumented VTs, not merely the clinical circuit.
• The lower success than in ischaemic cardiomyopathy is attributed to the septal, midmyocardial and perivalvular distribution of NICM scar, which limits catheter access and transmural lesion delivery.
• The authors suggest endo-epicardial homogenization as an initial strategy for NICM patients with demonstrable low-voltage scar.

Limitations of the document

• Non-randomised, operator-selected groups. The comparison is prospective but allocation was by preference, so indication and operator biases cannot be excluded.
• Single centre, modest size. n=93 from one high-volume group; external validity is uncertain.
• Short follow-up. Mean 14±2 months is short for a disease with late recurrence, and there was no protocolised repeat mapping to assess scar progression.
• Selected population. All patients had low-voltage scar on bipolar mapping; findings do not apply to NICM without demonstrable scar, and the 16 excluded patients are not characterised.
• Inconsistent effect-size reporting. The abstract states a 41% relative risk reduction; the discussion states 59%; the reported HR of 0.48 corresponds to roughly 52%. The discrepancy is not explained.
• No adjustment for ablation era or technology. All procedures used conventional irrigated RF; the relevance to contemporary contact-force, high-density mapping or PFA workflows is unknown.
• No mortality or heart-failure endpoint. The study is powered for VA recurrence, not survival or LV function.

Key Concepts Mentioned

• concepts/VT-Ablation-Nonischemic-Cardiomyopathy — the substrate and strategy being tested
• concepts/VT-Ablation — general ablation principles and mapping
• concepts/Epicardial-VT-Ablation — the epicardial component of the strategy
• concepts/Late-Gadolinium-Enhancement — the imaging correlate of midwall/epicardial scar
• concepts/VT-Management — where ablation sits in overall care
• entities/DCM — the underlying cardiomyopathy

Key Entities Mentioned

• Biosense Webster — CARTO mapping system and ThermoCool irrigated catheter
• St. David's Medical Center, Texas Cardiac Arrhythmia Institute — coordinating centre

Wiki Pages Updated

• Created: wiki/sources/vt-ablation-nicm-jacc-2016.md
• Created: wiki/concepts/VT-Ablation-Nonischemic-Cardiomyopathy.md
• Updated: wiki/concepts/VT-Ablation.md
• Updated: wiki/entities/DCM.md
• Updated: wiki/concepts/VT-Management.md
• Updated: wiki/sourceindex.md
• Updated: log.md