#ventricular-tachycardia #catheter-ablation #substrate-mapping #entrainment-mapping #ablation-technology

VT Ablation

Definition

Catheter ablation of ventricular tachycardia (VT) is a percutaneous procedure that identifies and destroys the myocardial substrate responsible for re-entrant or focal ventricular arrhythmias. In scar-related VT, the target is the surviving myocardial channels and abnormal electrograms within scar; in focal VT or frequent ventricular premature depolarisations (VPDs), the target is the site of origin. Ablation is distinct from device therapy: an ICD terminates VT, whereas ablation attempts to prevent it. The field has moved from surgical subendocardial resection through direct-current and radiofrequency catheter ablation to electroanatomic substrate mapping and, most recently, to energy sources designed to create transmural ventricular lesions.

Key Concepts

Historical development

The first invasive VT therapy was surgical: aneurysmectomy in the 1950s, followed by Josephson's subendocardial resection (the "Pennsylvania peel") in 1979, guided by intraoperative activation mapping and carrying 5–15% operative mortality. (sources/vt-ablation-jaccep-2019, rating: high)
High-energy direct-current catheter ablation was introduced in 1983 and replaced by radiofrequency energy by the late 1980s; irrigated and larger-tip catheters subsequently increased lesion depth. (sources/vt-ablation-jaccep-2019, rating: high)
Stevenson's 1993 entrainment description of exit, central isthmus, entrance, inner loop, outer loop and bystanders remains the conceptual model for scar-related re-entry. (sources/vt-ablation-jaccep-2019, rating: high)
Sosa's 1996 percutaneous epicardial access extended ablation beyond the endocardium, and Marchlinski's 2000 electroanatomic substrate mapping allowed ablation of unmappable VT. (sources/vt-ablation-jaccep-2019, rating: high)

Mapping techniques

Activation mapping identifies the earliest pre-QRS electrogram (>20 ms, with a QS unipolar pattern) in focal VT, or the exit and diastolic isthmus in re-entry. Passive slow-conduction zones can mimic critical sites, so activation mapping alone is unreliable in re-entry. (sources/vt-ablation-jaccep-2019, rating: high)
Entrainment mapping confirms circuit participation: concealed fusion with a post-pacing interval (PPI) within 30 ms of the tachycardia cycle length (TCL). The stimulus-to-QRS/TCL ratio separates exit (<30%), central isthmus (30–50%), entrance (50–70%) and inner loop (>70%). (sources/vt-ablation-jaccep-2019, rating: high)
Pace mapping matches the paced QRS to the clinical VT; it localises a focal origin or the exit site in re-entry, but spatial resolution is only 11–26 mm and pacing at the entrance can produce a different QRS. (sources/vt-ablation-jaccep-2019, rating: high)
Substrate mapping defines normal myocardium (>1.5 mV), border zone and dense scar (<0.5 mV), then targets late potentials, local abnormal ventricular activities (LAVA), scar homogenisation, scar dechanneling or core isolation. It is essential when VT is unstable or unmappable. (sources/vt-ablation-jaccep-2019, rating: high)

Substrate targets and endpoints

Late potentials and LAVA are surrogate markers of slow-conduction channels; their abolition is associated with fewer recurrences in observational studies. (sources/vt-ablation-jaccep-2019, rating: high)
Scar homogenisation ablates all abnormal potentials within the scar rather than only the clinical circuit, on the rationale that "innocent islets" can sustain undocumented VTs. In non-ischaemic cardiomyopathy this strategy improved VA-free survival versus limited-substrate ablation (64% vs 39% at 14 months). (sources/vt-ablation-nicm-jacc-2016, rating: medium)
Core isolation surrounds the putative isthmus and aims for entrance and exit block; in a small series it was achieved in 84% and associated with better arrhythmia-free survival (89% vs 57%). (sources/vt-ablation-jaccep-2019, rating: high)
Non-inducibility after programmed stimulation remains the traditional endpoint, but it is imperfect and did not predict long-term success in the non-ischaemic homogenisation study. (sources/vt-ablation-jaccep-2019, rating: high) (sources/vt-ablation-nicm-jacc-2016, rating: medium)

Indications

Ablation is recommended over antiarrhythmic drugs (Class I) for symptomatic RVOT VPDs in a structurally normal heart, symptomatic idiopathic sustained monomorphic VT, recurrent monomorphic VT in ischaemic heart disease despite amiodarone, and bundle-branch re-entrant, fascicular or post-infarction Purkinje-mediated VT. (sources/vt-ablation-jaccep-2019, rating: high)
Most structural-heart-disease indications are conditional on antiarrhythmic drugs being ineffective, not tolerated or not the patient's preference — including non-ischaemic cardiomyopathy with recurrent monomorphic VT, ARVC with recurrent VT or ICD therapies, and ischaemic VT storm refractory to drugs. (sources/vt-ablation-jaccep-2019, rating: high)
Emergency ablation is Class I for sustained monomorphic VT causing electrical storm refractory to antiarrhythmic drugs. (sources/VA-SCD-ESC-2022, rating: very high)

Randomised evidence

Trial	Population	Comparison	Key result
SMASH-VT (2007)	Post-MI, secondary-prevention ICD	Prophylactic substrate ablation vs drugs	Freedom from ICD therapy 88% vs 67% (p=0.007); mortality NS
VTACH (2010)	Ischaemic, tolerated VT	Ablation before ICD vs ICD alone	Freedom from VA at 2 years 47% vs 29% (p=0.045); mortality same
VANISH (2016)	Ischaemic, VT despite AAD	Ablation + AAD vs AAD escalation	Composite 59.1% vs 68.5% (p=0.04); mortality same; more AAD adverse events
SMS (2017)	Ischaemic, unstable VT	Substrate ablation + ICD vs ICD	Event-free survival 49.0% vs 52.4% (NS); fewer VA episodes (2.8 vs 8.1)
VANISH2 (2025)	Post-MI, first-line therapy	Ablation vs sotalol/amiodarone	Composite 50.7% vs 60.6%; HR 0.75 (P=0.03); mortality and storm NS

VANISH2 is the first large trial to support ablation as first-line therapy rather than after drug failure; the benefit was driven by fewer treated sub-threshold VT episodes (HR 0.26), while mortality (HR 0.84) and VT storm (HR 0.95) were not significantly reduced. (sources/vt-ablation-vanish2-nejm-2025, rating: very high)
Across the earlier trials, the consistent signal is fewer ICD therapies and less drug toxicity, not a demonstrated mortality benefit. (sources/vt-ablation-jaccep-2019, rating: high)

Non-ischaemic and epicardial substrate

Non-ischaemic cardiomyopathy has patchy midwall/epicardial fibrosis, often anteroseptal or inferolateral and perivalvular; acute success is 38–73%, recurrence 46–60% at 1 year, and outcomes are worse than in ischaemic cardiomyopathy. (sources/vt-dcm-hrs-2018, rating: high)
In HELP-VT, 1-year VT-free survival was 40.5% in non-ischaemic versus 57.0% in ischaemic cardiomyopathy (p=0.039). (sources/vt-ablation-jaccep-2019, rating: high)
Epicardial mapping and ablation are required in 32–63% of non-ischaemic patients, and in ARVC, Chagas disease, Brugada syndrome and cardiac sarcoidosis. See concepts/Epicardial-VT-Ablation. (sources/epicardial-vt-ablation-jaccep-2024, rating: high)
See concepts/VT-Ablation-Nonischemic-Cardiomyopathy and concepts/VT-Ablation-Ischemic-Cardiomyopathy for substrate-specific detail.

Emerging technologies

Larger electrodes were the first answer to the depth problem. A 9-mm expandable lattice tip (effective surface area ≈275 mm² against 28 mm² for a 3.5-mm tip) delivered ~15× more current at half the current density, doubling ventricular lesion depth versus a conventional irrigated catheter in sheep and swine (10.3–10.5 vs 5.5–6.5 mm) while reducing steam pops, and catheter-tip-to-tip bipolar delivery with the same electrode produced 80% transmurality at 15.8 mm. (sources/lattice-tip-rf-lesion-circep-2019, rating: medium) (sources/lattice-tip-rf-lesion-jce-2019, rating: medium)
The platform now carries both energy modes and is in clinical use; see entities/Sphere-9.
High-voltage focal pulsed field ablation (PFA) produced 12.5-mm-deep, 23.3-mm-wide ventricular lesions in pigs and, in the first-in-human VCAS trial, 92% acute success, 81.8% 180-day freedom from VT/VF or ICD shock and a 98% reduction in VT/VF burden. (sources/pfa-vt-circ-2025, rating: high)
Endocardial-only high-voltage PFA abolished epicardial abnormal potentials in 9/9 patients with paired epicardial mapping, suggesting transmural lesions without epicardial access. (sources/pfa-vt-circ-2025, rating: high)
Monopolar PFA has a depth ceiling of 6–8 mm irrespective of waveform or catheter design, which is why off-label atrial catheters eliminated endocardial but not epicardial circuits, and why depth — not energy — is the field's central problem. (sources/pfa-af-ehra-2026, rating: very high) (sources/pfa-vt-case-series-jacep-2023, rating: low)
Dual-energy lattice-tip systems map rapidly (~4,500 points in ~18 minutes) and achieve 89% acute non-inducibility, but pace mapping and entrainment are often impossible with the small surface electrodes, and epicardial PFA is not transmural. (sources/lattice-tip-vt-europace-2024, rating: medium)
The AVAAR registry (n=126, 64% redo) is the largest ventricular PFA dataset: 84% acute success, 72% free of recurrence at 5.6 ± 3.7 months (de novo 80% vs redo 68%) and 6% major acute complications — comparable to RF benchmarks of 3.8–11.2% in similar populations. (sources/avaar-registry-europace-2025, rating: high)
Bipolar PFA between two catheter tips reaches 87% transmurality at 14.3 mm in swine, the deepest lesion yet reported, but causes transient complete heart block within 1 cm of the aortic cusp. (sources/lattice-tip-preclinical-circep-2024, rating: medium)
Other approaches to deeper lesions include half-normal saline irrigation, impedance modulation, simultaneous unipolar and bipolar ablation, and a retractable needle-tip catheter; none has been tested in a large randomised trial. (sources/vt-ablation-jaccep-2019, rating: high)
Alternatives to radiofrequency include cryoablation for papillary-muscle targets, transcoronary or coronary venous ethanol for intramyocardial circuits, and stereotactic body radiotherapy guided by non-invasive mapping. (sources/vt-ablation-jaccep-2019, rating: high)
See concepts/Ventricular-PFA for the full evidence base and device comparison.

Referral timing and systems of care

In a tertiary centre, 63% of structural-heart-disease referrals were late (≥2 prior VT episodes separated by ≥1 month); early referral was associated with a lower recurrence risk after ablation (HR 0.37, p=0.02). (sources/vt-ablation-jaccep-2019, rating: high)
Ablation can allow amiodarone dose reduction or discontinuation, which matters because long-term amiodarone toxicity is a major source of morbidity. (sources/vt-ablation-jaccep-2019, rating: high)
Procedures for unstable VT may require temporary mechanical support (pLVAD or ECMO); the PAAINESD score identifies high-risk patients, but prophylactic support has not been tested in a randomised trial. (sources/vt-ablation-jaccep-2019, rating: high)

Contradictions / Open Questions

Mortality benefit remains unproven. VANISH2 and its predecessors show fewer ICD therapies and fewer drug adverse events, but no trial has demonstrated a significant mortality reduction. Whether the composite endpoint is the right outcome, and whether ablation improves survival in selected patients, is unresolved. (sources/vt-ablation-vanish2-nejm-2025, rating: very high) (sources/vt-ablation-jaccep-2019, rating: high)
The best procedural endpoint is uncertain. Non-inducibility is the traditional gold standard, but it failed to predict long-term success in the non-ischaemic homogenisation study, and physiological endpoints such as core isolation, dechanneling and LAVA abolition have not been compared prospectively. (sources/vt-ablation-nicm-jacc-2016, rating: medium) (sources/vt-ablation-jaccep-2019, rating: high)
Non-ischaemic evidence is weaker than ischaemic evidence. There is no randomised trial of ablation versus drugs in non-ischaemic cardiomyopathy, and the homogenisation study was non-randomised with operator-selected groups and 14-month follow-up. (sources/vt-ablation-nicm-jacc-2016, rating: medium) (sources/vt-dcm-hrs-2018, rating: high)
Transmurality is a double-edged sword. Deeper lesions may eliminate intramural circuits, but they also ablate viable myocardium and may worsen contractility; the optimal lesion depth and the patients in whom transmural homogenisation is worth the trade-off are unknown. (sources/pfa-vt-circ-2025, rating: high)
First-line ablation versus drugs is not settled across substrates. VANISH2 supports first-line ablation in post-MI VT, but it excluded non-ischaemic cardiomyopathy, and guidelines still recommend drugs first for many patients. (sources/vt-ablation-vanish2-nejm-2025, rating: very high)
Early referral is observational. The HR 0.37 for early referral comes from a single-centre cohort and is vulnerable to selection bias; no randomised trial has tested a strategy of earlier ablation. (sources/vt-ablation-jaccep-2019, rating: high)
PFA efficacy is promising but unconfirmed. VCAS was a single-arm first-in-human study of 26 patients with 6-month follow-up and a 95% CI extending to 67%, which overlaps conventional ablation outcomes; randomised comparison is required. (sources/pfa-vt-circ-2025, rating: high)
Ventricular PFA has a depth problem rather than an efficacy problem. Monopolar delivery plateaus at 6–8 mm, epicardial circuits survive endocardial ablation, and the strategies that increase depth (bipolar, dual-energy, high-voltage focal) all add conduction-system and coronary risk; no study has compared them against each other. (sources/pfa-af-ehra-2026, rating: very high) (sources/lattice-tip-preclinical-circep-2024, rating: medium)
Every ventricular PFA dataset is single-arm and short. AVAAR, the lattice-tip series and VCAS all report 3–6 month freedom rates in populations with 64–66% prior failed ablation, without a concurrent RF comparator; whether PFA changes outcomes rather than simply achieving them differently is untested. (sources/avaar-registry-europace-2025, rating: high) (sources/lattice-tip-vt-europace-2024, rating: medium)

Connections

Related to concepts/VT-Ablation-Ischemic-Cardiomyopathy — the best-evidenced substrate and first-line VANISH2 strategy
Related to concepts/VT-Ablation-Nonischemic-Cardiomyopathy — intramural and epicardial substrate, scar homogenisation
Related to concepts/Epicardial-VT-Ablation — access, mapping and complications of the epicardial approach
Related to concepts/Ventricular-PFA — ventricular PFA evidence, devices and the depth ceiling
Related to concepts/VT-Management — where ablation sits in acute and chronic care
Related to concepts/Electrical-Storm — emergency ablation and mechanical support
Related to concepts/Late-Gadolinium-Enhancement — imaging the arrhythmogenic substrate
Related to entities/ICD — device therapy and ICD programming as the comparator/adjunct
Related to entities/DCM — the non-ischaemic cardiomyopathy substrate
Related to entities/ARVC and entities/Brugada-Syndrome — epicardial-substrate conditions