• Patients with two or more documented spontaneous episodes of sustained symptomatic VT within 3 months or 1 sustained episode of VT or VT storm (two or more VTs in 24 hours) which required device therapy (shock or anti-tachycardia pacing), external cardioversion, escalated antiarrhythmic therapy, and / or hospitalization

‣ Documented episodes assessment will be performed by a review of ECGs, hospitalization records, and/or Implantable Cardioverter Defibrillator (ICD) interrogation

⁃ Patients must have an ICD implanted

• Age ≥18 years

• LVEF ≥ 30% as estimated by echocardiography, contrast ventriculography, radionuclide imaging or cardiac magnetic resonance imaging within the previous 30 days.

• Willing and capable of understanding the objective, risk, and requirement of the study, and providing consent.

• Able and willing to comply with all pre-, post- and follow-up testing and requirements.