Advisor HD Grid Observational Study

Inclusion Criteria: 1\. Subject must provide written informed consent for study participation and willing and able to comply with the protocol described evaluations and follow up schedule 2. Over 18 years of age 3. Indicated for cardiac electroanatomical mapping and RF ablation procedure to treat PersAF or VT 4. Subject is diagnosed with either PersAF OR VT as defined by: a. Persistent AF: i. Documented symptomatic persistent AF defined as continuous atrial fibrillation that is sustained beyond 7 days but less than 12 months b. VT: i. Sustained monomorphic ventricular tachycardia with record of VT event within last 6 months and history of prior myocardial infarction Exclusion Criteria: 1. Life expectancy less than 12 months 2. Women who are pregnant or nursing 3. Known intracardiac thrombus or myxoma verified within 48 hours of index ablation procedure 4. Myocardial infarction (MI) or unstable angina, or previous cardiac surgery within 60 days of index ablation procedure 5. Percutaneous coronary intervention (PCI) within 30 days of index ablation procedure 6. Documented cerebro-embolic event within the past 12 months (365 days) 7. History of valve repair, presence of a prosthetic valve, or severe mitral regurgitation thought to require valve replacement or repair within 12 months 8. Awaiting cardiac transplantation or other cardiac surgery within the next 12 months (365 days) 9. Current acute illness or active systemic infection or sepsis 10. Currently enrolled in another clinical study that could confound the results of this study 11. Any cause for contraindication to ablation procedure or systemic anticoagulation 12. Presence of other anatomic or comorbid conditions, or other medical, social, or psychological conditions that, in the investigator's opinion, could limit the subject's ability to participate in the clinical study or to comply with follow-up requirements, or impact the scientific soundness of the clinical study results. 13. Vulnerable patient or individuals whose willingness to volunteer in a study, in the judgement of investigator or public authorities, could be unduly influenced by lack of or loss of autonomy 14. Indication-specific exclusion criteria including: a. PersAF: i. PersAF felt to be secondary to electrolyte imbalance, uncontrolled thyroid disease, or reversible or non-cardiac cause. ii. Left atrial diameter (LAD) \> 55 mm (parasternal long axis view) iii. Left ventricular ejection fraction (LVEF) \< 40% iv. Uncontrolled heart failure or New York Heart Association (NYHA) function class III or IV v. Presence of implanted implantable cardioverter-defibrillator (ICD)/implantable cardiac resynchronization therapy defibrillator (CRT-D). b. VT: i. VT/Ventricular Fibrillation (VF) thought to be from channelopathies ii. Active ischemia or other reversible cause of VT iii. Incessant VT at time of procedure iv. Implanted with a ventricular assist device (VAD) (e.g. TandemHeart) v. Chronic NYHA Class IV heart failure vi. Ejection fraction \< 15% \-