Ventricular Tachycardia Ablation: Past, Present, and Future Perspectives
Authors, Journal, Affiliations, Type, DOI
- Authors: Gustavo S. Guandalini, Jackson J. Liang, Francis E. Marchlinski
- Journal: JACC: Clinical Electrophysiology 2019;5(12):1363–1383
- Affiliations: Electrophysiology Section, Hospital of the University of Pennsylvania; Electrophysiology Service, University of Michigan
- Type: State-of-the-art narrative review
- DOI: 10.1016/j.jacep.2019.09.015
Overview
This review traces VT ablation from surgical aneurysmectomy and subendocardial resection through direct-current and radiofrequency catheter ablation to contemporary electroanatomic substrate mapping. It sets out the four mapping techniques that remain the foundation of the field — activation, entrainment, pace and substrate mapping — with practical detail on circuit components and their responses to entrainment. It then summarises the 2019 consensus indications and the randomised trials that shaped them (SMASH-VT, VTACH, CALYPSO, VANISH, SMS) and identifies the field's unresolved problems: late referral, unstable VT, non-ischaemic intramural substrate, and the need for deeper lesions. The final section reviews emerging technologies, including low-ionic irrigants, impedance modulation, simultaneous unipolar and bipolar ablation, needle-tip catheters, alcohol ablation, pulsed field ablation and stereotactic radiotherapy.
Keywords
Catheter ablation; ventricular tachycardia; entrainment mapping; substrate mapping; non-ischaemic cardiomyopathy; pulsed field ablation
Key Takeaways
Historical evolution
| Year | Development |
|---|---|
| 1953 | First description linking apical aneurysm to VT |
| 1955–1959 | Aneurysmectomy with resolution of refractory VT (Bailey, Couch) |
| 1973 | Concomitant aneurysmectomy and coronary revascularisation advocated for refractory VT |
| 1979 | Josephson's subendocardial resection — the "Pennsylvania peel" — guided by intraoperative activation mapping; operative mortality 5–15% |
| 1983 | High-energy direct-current catheter ablation through a standard quadripolar electrode |
| Late 1980s–1990s | Radiofrequency replaces DC; irrigated and larger-tip catheters create deeper lesions |
| 1993 | Stevenson's entrainment-based description of exit, central isthmus, entrance, inner loop, outer loop and bystanders |
| 1996 | Sosa's percutaneous epicardial access for Chagas VT |
| 2000 | Marchlinski's electroanatomic substrate mapping and linear lesions for unmappable VT |
The four mapping techniques
- Activation mapping. Earliest pre-QRS local electrogram (>20 ms pre-QRS, QS unipolar pattern) identifies a focal origin; in re-entry, pre-QRS activity marks the exit, while mid-diastolic fractionated low-amplitude activity marks the isthmus. Passive slow-conduction zones can mimic these patterns, so activation mapping alone is unreliable in re-entry.
- Entrainment mapping. A critical circuit site shows concealed fusion, post-pacing interval (PPI) within 30 ms of the tachycardia cycle length (TCL), and a stimulus-to-QRS (S-QRS) equal to the electrogram-to-QRS interval.
| Circuit component | Fusion | PPI | S-QRS/TCL |
|---|---|---|---|
| Exit | Concealed | = TCL (±30 ms) | <30% |
| Central isthmus | Concealed | = TCL (±30 ms) | 30–50% |
| Entrance | Concealed | = TCL (±30 ms) | 50–70% |
| Inner loop | Concealed | = TCL (±30 ms) | >70% |
| Adjacent bystander | Concealed | > TCL | Variable |
| Outer loop | Manifest | = TCL (±30 ms) | <30% |
| Remote bystander | Manifest | > TCL | <30% |
Limitations: entrainment requires haemodynamic stability, may change the circuit, and cannot identify intramural components that are not accessible from either surface.
- Pace mapping. A paced QRS identical to the clinical VT identifies a focal origin or proximity to the exit in re-entry. Spatial resolution is low — a "perfect" match can be obtained 11–26 mm from the origin — and pacing at the entrance can produce a completely different QRS.
- Substrate mapping. Bipolar voltage >1.5 mV is normal and <0.5 mV is dense scar. Targets include late potentials, local abnormal ventricular activities (LAVA), scar homogenisation, scar dechanneling and core isolation. Non-inducibility remains the traditional gold standard but is imperfect and not validated against newer physiological endpoints.
Indications and the 2019 consensus
- 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 chronic amiodarone, and bundle-branch re-entrant, fascicular or post-infarction Purkinje-mediated VT.
- Most other structural-heart-disease indications are Class I or IIa only if antiarrhythmic drugs are ineffective, not tolerated or not the patient's preference, including NICM with recurrent monomorphic VT, ARVC with recurrent VT or ICD therapies, and ischaemic VT storm refractory to drugs.
- The only recommendation supported by Level A evidence was, at the time, Class IIb for catheter ablation after a first episode of monomorphic VT in ischaemic cardiomyopathy with an ICD. All other recommendations were Level B or C.
- This evidence architecture is the basis for the field's complaint that patients are referred late and that ablation is treated as a last resort.
Randomised trials
| Trial | Population | Comparison | Key result |
|---|---|---|---|
| SMASH-VT (2007) | 128 post-MI patients with secondary-prevention ICD | Prophylactic substrate ablation vs medical therapy | Freedom from any appropriate ICD therapy 88% vs 67% (p=0.007); shocks 91% vs 69% (p=0.003); mortality 9% vs 17% (NS) |
| VTACH (2010) | 107 ischaemic patients with haemodynamically tolerated VT | Ablation before ICD vs ICD alone | Freedom from recurrent VA at 2 years 47% vs 29% (p=0.045); time to recurrence 18.6 vs 5.9 months; mortality 8.5% vs 8.6% |
| CALYPSO (2015) | Ischaemic ICD patients with prior appropriate therapy | Ablation vs AAD | Terminated after 27 patients; 41% of those failing screening were excluded because of prior AAD use |
| VANISH (2016) | 259 ischaemic ICD patients with VT despite AAD | Ablation + continued AAD vs AAD escalation | Composite death/shock/storm 59.1% vs 68.5% (p=0.04); mortality 27.3% vs 27.6%; AAD adverse events 39 vs 20 (p=0.003), including 2 pulmonary and 1 hepatic death |
| SMS (2017) | 111 ischaemic patients with unstable VT | Substrate ablation + ICD vs ICD alone | Event-free survival 49.0% vs 52.4% (NS); spontaneous VA episodes 2.8 vs 8.1 (p=0.015) |
- Ongoing trials at the time included PARTITA (timing after first shock), PAUSE-SCD (pre-emptive ablation in structural heart disease), LESS-VT (sensor-enabled catheter) and VANISH2 (first-line ablation vs AAD).
Timing and unstable VT
- In the authors' centre, 63% of structural-heart-disease referrals were late (≥2 prior VT episodes separated by ≥1 month). Early referral was associated with a lower risk of recurrence after ablation (HR 0.37, p=0.02), an observational finding.
- For unstable VT, substrate-based strategies such as core isolation are used. In 44 patients, core isolation was achieved in 37 (84%) and was associated with better arrhythmia-free survival (89.2% vs 57.1%, p=0.013) over 17.5 months — small, non-randomised data.
- Temporary mechanical support (pLVAD or ECMO) permits mapping during unstable VT. The PAAINESD score (pulmonary disease, age, general anaesthesia, ischaemic cardiomyopathy, NYHA III/IV, LVEF <25%, VT storm, diabetes) identifies high-risk patients; prophylactic support may improve survival compared with rescue support in small series, but no randomised trial exists.
Non-ischaemic cardiomyopathy
- NICM substrate is anteroseptal or inferolateral, commonly perivalvular, intramural or epicardial; midmyocardial septal scar can be identified by LGE, slow transseptal activation, unipolar voltage abnormalities and septal coronary venous electrograms.
- In HELP-VT, 1-year VT-free survival was lower in NICM than ischaemic cardiomyopathy (40.5% vs 57.0%, p=0.039), and NICM patients required more repeat procedures and concomitant AAD therapy.
- The authors argue that the simple anteroseptal/inferolateral dichotomy is incomplete: anteroseptal scar often extends to the inferior septum, LV summit and anterolateral perivalvular regions.
Emerging technologies
- Deeper RF lesions: half-normal saline or dextrose irrigation, impedance modulation with additional surface patches, simultaneous unipolar ablation from two catheters, bipolar ablation between two catheters, and a retractable 27-gauge needle-tip electrode for intramyocardial delivery. Each increases lesion size but also the risk of steam pops, stroke and tissue disruption.
- Alternative energies: cryoablation for papillary-muscle instability; transcoronary arterial or retrograde coronary venous ethanol for intramyocardial circuits; pulsed field ablation, which avoids barotrauma and spares coronary arteries in animal models; stereotactic body radiotherapy guided by non-invasive substrate mapping, with phase I/II efficacy but unresolved long-term toxicity and motion management.
Limitations of the document
- Narrative review, not a systematic review or meta-analysis. Trial selection and emphasis reflect the authors' perspective; no formal risk-of-bias assessment is provided.
- Published in 2019. It predates VANISH2, the first-in-human ventricular PFA experience, modern contact-force/high-density workflows and contemporary guideline revisions; its "future" section is now partly historical.
- Trial descriptions are condensed. Several trials are summarised in a few sentences, and subgroup and safety details are omitted.
- Single-centre procedural experience. The timing, core-isolation and mechanical-support sections draw heavily on the authors' institutional practice, which may not generalise.
- Indication table is a snapshot. The Class IIb/Level A statement for first-episode monomorphic VT is presented without discussion of its evidential weakness, and subsequent guidelines have changed several recommendations.
- No patient-level or pooled outcome data. The review does not estimate effect sizes across trials or adjust for differences in populations and ablation strategies.
Key Concepts Mentioned
- concepts/VT-Ablation — the subject of the review
- concepts/VT-Ablation-Ischemic-Cardiomyopathy — the best-evidenced substrate
- concepts/VT-Ablation-Nonischemic-Cardiomyopathy — the intramural/epicardial challenge
- concepts/Epicardial-VT-Ablation — the epicardial approach pioneered by Sosa
- concepts/Ventricular-PFA — a future energy source at the time of writing
- concepts/Electrical-Storm — a key indication for emergency ablation
- concepts/VT-Management — the broader management pathway
- entities/ICD — the device context for most ablation trials
Key Entities Mentioned
- Hospital of the University of Pennsylvania
- University of Michigan
- Biosense Webster, Abbott, Boston Scientific, Medtronic — mapping and ablation platforms discussed
Wiki Pages Updated
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wiki/sources/vt-ablation-jaccep-2019.md - Created:
wiki/concepts/VT-Ablation.md - Updated:
wiki/concepts/VT-Ablation-Ischemic-Cardiomyopathy.md - Updated:
wiki/concepts/VT-Management.md - Updated:
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