HRHF Clinic

Idiopathic VT is ventricular tachycardia that occurs in a heart that is otherwise structurally normal — no scar, no weakened muscle, no genetic disease. The heart pumps well, the valves are normal, the arteries are clear. The VT arises from a single focal site, most commonly the right or left ventricular outflow tract or the fascicles of the left bundle. This is generally a benign condition that does not shorten life expectancy. But it can cause significant symptoms — palpitations, breathlessness, dizziness — and can be very effectively cured with ablation.

If you have been diagnosed with idiopathic VT, the most important message is reassurance. Your heart is normal. The arrhythmia is treatable. Ablation in expert hands cures idiopathic VT in over 90 percent of cases — and even technically demanding cases that originate deep within the muscle between the two outflow tracts can now be successfully ablated using bipolar techniques.

Idiopathic VT mapping uses PASO pace-matching extensively — because the VT may not be sustained long enough for activation mapping, we reproduce the VT morphology by pacing from each candidate site and identify the location whose paced beat most closely matches the clinical VT. Carto provides the 3D anatomical context.

For most idiopathic VTs, focal radiofrequency ablation at the earliest activation point eliminates the arrhythmia. For deep intramural circuits between the right and left outflow tracts — historically very difficult to ablate — we use bipolar ablation with one catheter in the RVOT and one in the LVOT, delivering energy across the intervening myocardium.

Scar-mediated VT is ventricular tachycardia that arises from areas of damaged or fibrotic heart muscle — most commonly after a previous heart attack, but also in patients with cardiomyopathy of any cause. The scar tissue itself does not conduct, but channels of surviving muscle running through the scar can act as the slow-conduction zone of a reentry circuit, sustaining the VT.

This is the substrate most patients fear — and it does require serious expert care. But modern ablation has transformed outcomes for scar VT. With proper substrate mapping, the channels within the scar can be identified and eliminated. Many patients who have suffered repeated ICD shocks become shock-free after a successful scar VT ablation.

If you have an ICD and have had VT episodes — even if you are currently on medications — a discussion about ablation may be appropriate. Modern guidelines support ablation as first-line therapy for many scar VT patients, ahead of escalating anti-arrhythmic drugs.

Scar VT mapping requires high-density substrate definition. We use Confidense mapping with multipolar catheters to acquire thousands of points across the affected chamber, identifying the precise location and architecture of scar zones, channels, and late potentials.

The ablation strategy depends on the individual circuit — sometimes targeting the critical isthmus during sustained VT (entrainment-guided), sometimes ablating all identified channels and late potentials (substrate-based), often a combination. PASO software supports identification of the VT exit site when activation mapping cannot be performed.

For deep intramural circuits unreachable from one surface, bipolar ablation between endocardial and epicardial catheters provides the depth needed.

Arrhythmogenic Right Ventricular Cardiomyopathy — ARVC — is a genetic disease in which the right ventricle progressively develops fibrofatty scar, particularly in the epicardial layers. VT in ARVC arises from these fibrofatty regions and is often a presenting feature of the disease. ARVC can affect young people, including athletes, and the diagnosis often comes as a shock.

If you have been diagnosed with ARVC, you are likely under the care of a cardiologist who has discussed an ICD and exercise restrictions. What may not have been discussed is that VT ablation in ARVC has improved dramatically in the last decade — particularly when epicardial access is part of the strategy. Many ARVC patients can have their VT burden significantly reduced or eliminated, allowing them to live with fewer ICD shocks and a better quality of life.

ARVC VT typically requires both endocardial and epicardial mapping — because the substrate is predominantly epicardial in this condition, endocardial-only ablation often fails. We routinely perform sub-xiphoid epicardial access for ARVC ablation.

Carto Confidense mapping defines the substrate on both surfaces; the epicardial map characteristically shows extensive low-voltage areas with scattered late potentials in the right ventricular free wall. Ablation targets all abnormal substrate — late potentials, fractionated electrograms, channels — across endocardial and epicardial surfaces. This is technically demanding work and not routinely available outside high-volume EP centres.

Some VT circuits originate from the outer surface of the heart — the epicardium — rather than the inner chamber. These epicardial circuits cannot be reached from inside the heart, and conventional endocardial ablation will fail to eliminate them. This is a recognised reason for ablation failure at centres that do not perform epicardial access.

Epicardial ablation involves a small puncture below the breastbone, through which a thin catheter is advanced into the pericardial space — the thin sac surrounding the heart. From here, the outer surface of the heart can be mapped and ablated. The procedure is performed under sedation, takes approximately 2 to 3 hours in addition to standard endocardial mapping, and has a well-established safety profile in experienced hands.

Epicardial access is part of routine practice at HRHF Clinic — used for ARVC, HCM, idiopathic VT with epicardial origin, and re-do scar VT where endocardial ablation has previously failed. If you have been told that your VT cannot be ablated, or that a previous ablation has failed, an epicardial approach may be the answer.

Sub-xiphoid percutaneous epicardial access uses the technique pioneered by Sosa and colleagues — a needle puncture into the pericardial space under fluoroscopic guidance, followed by sheath placement and catheter advancement. We perform this routinely at HRHF Clinic, with the same Carto mapping system used endocardially.

Mapping and ablation strategies are the same as endocardial — voltage mapping, late potential identification, activation or PASO mapping during VT, and lesion delivery — but on the epicardial surface. Pre-procedure coronary angiography is performed when ablation will be near major coronary vessels.

The combination of routine endocardial-epicardial mapping is what allows HRHF Clinic to treat VT substrates that other centres decline.

Hypertrophic Cardiomyopathy — HCM — is a genetic disease causing thickening of the heart muscle. VT in HCM has historically been considered very difficult to ablate, and many HCM patients with recurrent VT have been managed primarily with ICDs and anti-arrhythmic drugs. This is changing.

With advances in mapping technology, bipolar ablation, and epicardial access, VT in HCM can now be successfully ablated in selected patients — particularly those with apical aneurysms, mid-cavity obstruction with apical scar, or focal scar substrate. HRHF Clinic has experience treating HCM VT, including patients with apical aneurysms — a recognised high-risk subgroup.

If you have HCM and have had VT episodes or appropriate ICD shocks, a discussion about ablation may be worthwhile — even if you have been told previously that ablation is not an option.

HCM VT often involves deep intramural circuits within thickened, scarred myocardium — substrates that conventional unipolar endocardial ablation cannot reach. Our approach combines:

• Detailed substrate mapping with Carto Confidense to identify scar and channels
• PASO pace-matching where activation mapping is not feasible
• Bipolar ablation for deep septal or intramural circuits
• Epicardial access for circuits that cannot be eliminated from the endocardium alone — particularly relevant in HCM with apical aneurysm