Sudden cardiac death (SCD) due to recurrent ventricular tachycardia (VT) is an important clinical sequela in patients with structural heart disease. VT generally occurs as a result of electrical re-entry in the presence of arrhythmogenic substrate (scar). Scar tissue forms due to an ischemic cardiomyopathy (ICM) from prior coronary obstructive disease or a non-ischemic cardiomyopathy (NICM) from an inflammatory or genetic disease.

AADs can reduce VT recurrence, but have significant limitations in treatment of VT. For example, amiodarone has high rates of side effects/toxicities and a finite effective usage before recurrence. ICDs prevent cardiac arrest and sudden death from VT, but do not stop VT occurring. Recurrent VT and ICD therapies decrease QOL, increase hospital visits, mortality, morbidity and risk of death. Improvement in techniques for mapping and ablation of VT have made CA an alternative.

Currently, there is limited evidence to guide clinicians either toward AAD therapy or CA in patients with NICM. This data shows significant benefit of CA over medical therapy in terms of VT free survival, survival free of VT storm and VT burden. Observational studies suggest that CA is effective in eliminating VT in NICM patients who have failed AADs, resulting in reduction of VT burden and AAD use over long term follow up. Furthermore, there is limited data on the efficacy of CA in early ICM with VT, or advanced ICM with VT. RCT data is almost exclusively on patients with modest ICM with VT, and this is not representative of the real-world scenario of patients with structural heart disease presenting with VT.

Therefore the primary objective is to determine in all patients with structural heart disease and spontaneous or inducible VT, if catheter ablation compared to standard medical therapy with anti-arrhythmic drugs results in a reduction of a composite endpoint of recurrent VT, VT storm and death at a median follow up of 18 months.

Inclusion Criteria:

Patients will be eligible for inclusion if they have:

1. ≥1 prior episode of sustained VT in the prior 6 months;

   1. Spontaneous VT: ≥1 episode of monomorphic VT treated by anti-tachycardia pacing (ATP) and/or internal shock by an ICD; lasting ≥30 seconds in the absence of intra-cardiac device therapy that could either be self-terminating or require reversion by pharmacological therapy or external cardioversion;
   2. Spontaneous VT: ≥1 episode of sustained spontaneous monomorphic VT lasting ≥30 seconds documented on Holter, ECG, Loop recorder or other cardiac monitoring device that could either be self-terminating or require reversion by pharmacological therapy or external cardioversion;
   3. Inducible VT: with syncope or palpitations - inducible VT defined as sustained monomorphic VT of CL ≥200 ms lasting for ≥10 s during a cardiac electrophysiology study (note with 4 extrastimuli with or without provocation with isoprenaline);

2. Already a recipient of an implanted cardiac device such as a pacemaker, defibrillator or a cardiac resynchronisation therapy device and/or is indicated to receive one given a new diagnosis of structural heart disease, based on current guideline recommendations;

3. Aged ≥18 years.

Exclusion Criteria:

Patients will be excluded if they are:

1. Unable or unwilling to provide informed consent or patients physician feels there is not significant equipoise to justify randomisation;
2. Women who are pregnant, breast feeding;
3. Medical illness with an anticipated life expectancy <3 months;
4. Unable to complete study procedures or unwilling to be followed up;
5. Have a concomitant illness, physical impairment or mental condition which in the opinion of the study team/ primary care physician could interfere with the conduct of the study including outcome assessments;
6. Known channelopathy such as long QT, short QT, Brugada syndrome, catecholaminergic polymorphic VT;
7. Known prior diagnosis of no structural heart disease, or idiopathic ventricular arrhythmia.

Randomisation will be performed using a secure, password-protected web portal (REDCap) and the allocation sequence will be blinded to investigators and participants until the participants have been deemed eligible and enrolled in the study. It will not be possible to maintain blinding after study enrolment because the intervention is invasive.

Outcome verification will be blinded.