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Procedure

VT Ablation

Substrate and activation-based catheter ablation of ventricular tachycardia. Strategy varies by substrate — idiopathic outflow tract VT differs fundamentally from scar-mediated VT in ischemic cardiomyopathy.

Typical duration
4–6 h
Sedation
General

Equipment & setup

  • ▸Femoral venous and arterial access kits, often bilateral
  • ▸Long sheath for LV access (transseptal or retrograde aortic)
  • ▸Intracardiac echo for chamber visualization and effusion monitoring
  • ▸3D electroanatomic mapping system with high-density multipolar catheter (PentaRay, HD Grid, Octaray)
  • ▸Contact-force irrigated ablation catheter, 4–8 mm tip
  • ▸Pericardial access kit for epicardial cases
  • ▸External defibrillator with multi-pad placement and hemodynamic support readiness (Impella, ECMO availability)
  • ▸Programmed stimulator with full induction protocols
  • ▸Activated clotting time monitor and heparin
  • ▸Pre-procedure cardiac MRI imaging integrated into the mapping system when available

Common pitfalls

  • ▸Inducing hemodynamically intolerable VT without a hemodynamic support plan in place
  • ▸Mapping the wrong substrate — failure to integrate imaging, ECG morphology, and pace-mapping
  • ▸Inadequate epicardial assessment in non-ischemic cardiomyopathy (substrate often subepicardial)
  • ▸Phrenic nerve and coronary artery injury during epicardial ablation — always map both before ablating
  • ▸Heart block during septal ablation near conduction system
  • ▸Failure to retest induction after waiting period — early non-inducibility can be misleading

Indications

  • Recurrent monomorphic VT with structural heart disease, particularly with ICD shocks
  • VT storm — three or more sustained episodes in 24 hours despite optimal medical therapy
  • Drug-refractory or drug-intolerant VT
  • Idiopathic VT (RVOT, LVOT, fascicular) — often first-line given high success and low risk
  • Bundle branch reentry VT — curable with right bundle ablation
  • Incessant VT causing tachycardia-mediated cardiomyopathy

Pre-procedure prep

  • Imaging: TTE, cardiac MRI with gadolinium for scar characterization (especially in non-ischemic CM), coronary anatomy review
  • ICD interrogation: review stored EGMs for VT morphology and cycle length; program to monitor-only or extend detection during ablation
  • Antiarrhythmics: amiodarone often continued; mexiletine may be added to facilitate VT slowing for mapping
  • Anticoagulation: hold DOAC per usual protocol; continuous heparin during LA or LV work
  • Anesthesia: general anesthesia, arterial line, large-bore venous access, defibrillator pads
  • Hemodynamic support planning: discuss Impella or ECMO availability for high-risk cases (low EF, history of unstable VT)
  • Multidisciplinary discussion for complex cases — heart failure, CT surgery backup, anesthesia

Setup & equipment

  • Vascular access: bilateral femoral venous, femoral arterial for LV mapping
  • ICE for chamber visualization, papillary muscle and septal anatomy, effusion surveillance
  • Heparin to ACT 300–350 for LV work
  • Multipolar mapping catheter essential for high-density substrate maps

Technique

Mapping strategy by substrate

Idiopathic outflow tract VT

  • Induce VT with isoproterenol, programmed stimulation, or burst pacing
  • Activation mapping during tachycardia — find the earliest site (often 20–40 ms pre-QRS)
  • Pace-map the target site and confirm 12/12 lead match with clinical VT
  • Ablate at the site of earliest activation
  • Common locations: RVOT septum, LVOT (aortic cusps, LV summit), pulmonary artery, papillary muscles

Scar-mediated VT (ischemic CM)

  • Build a bipolar voltage map in sinus rhythm: <0.5 mV is dense scar, 0.5–1.5 mV is border zone
  • Identify late potentials and local abnormal ventricular activities (LAVA) within the scar
  • Channel identification: bands of preserved voltage within scar that house the reentry circuit
  • Substrate modification: ablate all late potentials and channels, with or without inducing VT
  • Increasingly the preferred strategy because it avoids dependence on tolerated VT mapping

Non-ischemic cardiomyopathy

  • Substrate often midmyocardial or epicardial — integrate MRI scar imaging into the map
  • Endocardial-only ablation often fails; epicardial access frequently required
  • Common patterns: basal lateral (Chagas-like), septal (sarcoid), free wall

Bundle branch reentry

  • His and right bundle recording essential
  • Diagnosis: VA dissociation absent, HV during VT longer than sinus
  • Ablate the right bundle — small lesion, definitive cure
  • Counsel about increased likelihood of needing CRT given underlying LV dysfunction

Activation and entrainment mapping (when VT tolerated)

  • Identify mid-diastolic potentials
  • Entrain from candidate sites: PPI – TCL <30 ms identifies the circuit
  • Concealed entrainment with matching stim-to-QRS interval identifies the critical isthmus
  • Ablate during VT; termination during energy delivery within 10–20 s is highly predictive of success

Epicardial access

  • Sosa subxiphoid approach under fluoroscopy
  • Tuohy needle, micropuncture wire, dilator, then sheath
  • Always confirm pericardial entry with contrast before sheath placement
  • Map coronaries and phrenic nerve before ablation — pace-map for phrenic capture and inject contrast for coronary proximity
  • Lower power settings on the epicardium; cool tip irrigation

Endpoints

  • Non-inducibility of any sustained VT with aggressive programmed stimulation (up to triple extrastimuli from two sites at two cycle lengths, with isoproterenol)
  • Elimination of all late potentials within the substrate
  • Pace-mapping mismatch at targeted sites
  • Acknowledge that complete non-inducibility isn’t always achievable — partial substrate modification still reduces ICD shock burden

Complications

  • Vascular complications: ~2–3%, higher with multiple accesses and arterial work
  • Tamponade: ~1–2%, higher with epicardial cases
  • Stroke: 1–2% in LV mapping cases
  • Heart block: variable, depends on substrate location
  • Acute hemodynamic decompensation: real risk in unstable substrate — plan support upfront
  • Phrenic nerve injury and coronary injury in epicardial cases
  • Mortality: 1–3% in published series, concentrated in VT storm and advanced HF populations

Post-procedure care

  • ICU or step-down monitoring for the first night, longer for high-acuity cases
  • Telemetry for at least 24 hours; reprogram ICD before discharge with detection zones restored
  • Anticoagulation for 4–6 weeks after LV ablation
  • Antiarrhythmics: often continued, with reassessment at 6–12 weeks
  • Heart failure optimization continues — VT ablation is not a substitute for guideline-directed therapy
  • Follow-up in 2–4 weeks with device interrogation, then 3 months, then per ICD shock surveillance
  • Counsel on realistic expectations: substantial reduction in shocks is the typical outcome; complete VT freedom is less common in advanced substrate

Watch

Short videos to help illustrate this topic. Embedded from the original channels — content belongs to them.

Video pending Add a youtube video ID to display: Substrate mapping in post-infarct VT
Substrate mapping in post-infarct VT · EP teaching channel · Bipolar/unipolar voltage mapping and channel identification.
Video pending Add a youtube video ID to display: Epicardial access — subxiphoid approach
Epicardial access — subxiphoid approach · EP teaching channel · Sosa technique and pericardial entry.

Last reviewed by Dr. Colombowala on May 22, 2026.

Not medical advice. This page is educational. Your situation may differ — discuss it with Dr. Colombowala or your treating physician before making decisions.