VT Ablation in Nonischemic Cardiomyopathy
Definition
Catheter ablation for ventricular tachycardia (VT) in non-ischaemic cardiomyopathy (NICM) targets scar-related re-entry in patchy, midmyocardial or epicardial fibrosis rather than the subendocardial infarct scar typical of ischaemic cardiomyopathy. The substrate is more often basal, perivalvular, septal or intramural, and it is frequently inaccessible to endocardial radiofrequency delivery. Ablation is recommended for recurrent monomorphic VT when antiarrhythmic drugs are ineffective, not tolerated or not desired, and as an emergency procedure for drug-refractory VT storm.
Key Concepts
Substrate patterns
- NICM fibrosis is patchy, interstitial or diffuse, unrelated to coronary supply, with two dominant patterns: intramural anteroseptal and subepicardial inferolateral. (sources/vt-dcm-hrs-2018, rating: high)
- Anteroseptal scars carry a higher ablation failure rate; inferolateral scars are more often approached epicardially. (sources/vt-dcm-hrs-2018, rating: high)
- The anteroseptal/inferolateral dichotomy is an oversimplification: anteroseptal scar often extends to the inferior septum, LV summit and anterolateral perivalvular regions. (sources/vt-ablation-jaccep-2019, rating: high)
- Midmyocardial septal scar can be recognised by late gadolinium enhancement, slow transseptal activation during basal septal pacing, unipolar voltage abnormalities and abnormal septal coronary venous electrograms. (sources/vt-ablation-jaccep-2019, rating: high)
- ECG prediction: RBBB VT with inferior axis and positive concordance, or LBBB VT with transition ≤V3, suggests anteroseptal substrate; RBBB VT with transition ≥V5 suggests inferolateral scar. (sources/vt-dcm-hrs-2018, rating: high)
Outcomes with conventional ablation
- Acute success ranges from 38% to 73%, recurrence 46–60% at 1 year, and complications reach 9% across heterogeneous single-centre series. (sources/vt-dcm-hrs-2018, rating: high)
- Non-inducibility is the traditional procedural endpoint, and low LVEF, prior VT storm, high VT burden and failed antiarrhythmic trials predict recurrence. (sources/vt-dcm-hrs-2018, rating: high)
- In HELP-VT, 1-year VT-free survival was 40.5% in NICM versus 57.0% in ischaemic cardiomyopathy (p=0.039), and NICM patients required more repeat procedures and concomitant drug therapy. (sources/vt-ablation-jaccep-2019, rating: high)
Endo-epicardial scar homogenisation (Gökoglan 2016)
- Prospective, single-centre, non-randomised comparison of 93 patients with dilated NICM (LVEF <40%, no significant coronary disease), monomorphic scar-related VT, an ICD and bipolar voltage <1.5 mV. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- Allocation by operator preference: standard limited-substrate ablation (n=57) versus endo-epicardial homogenisation of all abnormal potentials within the scar (n=36).
- Epicardial mapping was performed in 100% of the homogenisation group and 52.6% of the standard group; RF time was longer (43.6 vs 21.2 min) and fluoroscopy time longer.
- Acute non-inducibility of any VT: 69.4% vs 42.1% (p=0.01). Non-inducibility of the clinical VT was not significantly different (77.8% vs 63.2%, p=0.138).
- Freedom from any VA after a single procedure at 14±2 months: 63.9% vs 38.6% (log-rank p=0.031).
- Rehospitalisation: 8.3% vs 26.3% (p=0.035).
- Procedural complications: 5.6% vs 21% (p=0.042), mainly access complications in patients requiring mechanical support.
- Multivariate predictors: homogenisation HR 0.48 (95% CI 0.27–0.96; p=0.027) and LVEF HR 0.93 per percentage point (0.91–0.98; p=0.008).
- Non-inducibility at the end of the procedure did not predict long-term success in this cohort.
- Among the 13 homogenisation-group recurrences, 9 (69.2%) had incomplete substrate elimination because of septal/midmyocardial scar (n=6) or perivalvular scar near the mitral annulus with overlying fat or coronary arteries (n=3).
The epicardial component
- Epicardial ablation is required in 32–63% of NICM patients, reflecting the high proportion of midmyocardial and epicardial substrate, especially around the basal perivalvular regions. (sources/epicardial-vt-ablation-jaccep-2024, rating: high)
- Epicardial access carries specific risks — haemopericardium 5–14% at access, phrenic nerve injury 0–1%, pericarditis up to 30% — and should be planned rather than incidental. See concepts/Epicardial-VT-Ablation. (sources/epicardial-vt-ablation-jaccep-2024, rating: high)
- A negative endocardial bipolar voltage map does not exclude epicardial scar: endocardial unipolar voltage <5.5 mV in the LV suggests deeper substrate. (sources/epicardial-vt-ablation-jaccep-2024, rating: high)
Practical strategy
- Start with endocardial mapping and ablation; proceed to epicardial mapping when VT remains inducible, when entrainment fails to identify a critical isthmus, or when unipolar voltage suggests intramural/epicardial scar. (sources/epicardial-vt-ablation-jaccep-2024, rating: high)
- Consider homogenisation when scar is well defined and accessible; recognise that septal, midmyocardial and perivalvular scar may remain untreatable with conventional RF. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- Non-inducibility should not be treated as a sufficient endpoint in NICM; document substrate modification and consider repeat mapping for recurrence. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- New energy sources designed for transmural lesions may change the feasibility of homogenisation; high-voltage PFA achieved epicardial potential elimination from an endocardial-only approach in a small first-in-human cohort. (sources/pfa-vt-circ-2025, rating: high)
Contradictions / Open Questions
- The homogenisation benefit is not randomised. Groups were allocated by operator preference, the homogenisation group had lower LVEF (29% vs 32%), and the study was single-centre with 14-month follow-up. Confounding by operator and case selection cannot be excluded. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- The effect size is reported inconsistently. The abstract states a 41% relative risk reduction, the discussion states 59%, and the HR of 0.48 corresponds to roughly 52%; the discrepancy is unexplained. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- Non-inducibility paradox. The strategy that improved outcomes also produced higher acute non-inducibility, yet non-inducibility itself did not predict long-term success. This suggests that the benefit comes from substrate modification beyond the clinical circuit, not from the conventional endpoint. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- NICM is heterogeneous. Dilated cardiomyopathy includes TTN, LMNA, FLNC, sarcoid, myocarditis and other aetiologies with different scar patterns and arrhythmic risk; no study has tested whether the benefit of homogenisation varies by genotype or aetiology. (sources/vt-dcm-hrs-2018, rating: high)
- No mortality or heart-failure benefit has been shown. The trial was powered for VA recurrence, not survival or LV function, and more extensive ablation could theoretically worsen contractility. (sources/vt-ablation-nicm-jacc-2016, rating: medium)
- Epicardial access may be overused or underused. The optimal threshold for epicardial mapping, and whether upfront epicardial access improves outcomes compared with a staged approach, has not been tested. (sources/epicardial-vt-ablation-jaccep-2024, rating: high)
- Contemporary technology may change the comparison. The trial used conventional irrigated RF; contact-force sensing, high-density mapping and PFA may alter both success and complication rates. (sources/pfa-vt-circ-2025, rating: high)
Connections
- Part of concepts/VT-Ablation — the general ablation overview
- Related to concepts/Epicardial-VT-Ablation — access and mapping of the epicardial substrate
- Related to concepts/VT-Ablation-Ischemic-Cardiomyopathy — the ischaemic comparator with stronger randomised evidence
- Related to concepts/Late-Gadolinium-Enhancement — imaging of midwall and epicardial scar
- Related to concepts/VA-Risk-Stratification-DCM — arrhythmic risk and ICD selection
- Related to concepts/VT-Management — overall care pathway
- Related to entities/DCM — the underlying cardiomyopathy
- Related to concepts/Ventricular-PFA — emerging transmural energy delivery