Inclusion Criteria:  Referred for first AFCA procedure by their responsible physician. Persistent AF captured on ECG but not in continuous AF for more than 3 years. (Persistent AF will be defined as any continuous episode lasting longer than 7 days or requiring intervention to restore sinus rhythm after this time.)  Participants must have either:  Left Ventricular Ejection Fraction (LVEF) < 50% by echocardiogram during routine screening or within 12 months prior to enrolment day. The echo must have been performed >3 weeks after optimisation of HF and rate control therapies, otherwise repeat imaging will be performed after this has been achieved  With:  o NYHA functional status II-III at the enrolment visit.  Or:  o Left Ventricular Ejection Fraction (LVEF) >50% by echocardiogram during routine screening or within 12 months prior to enrolment day.  With:  o modified European Heart Rhythm Association 2a-4.  Exclusion Criteria:  Previous left atrial ablation procedure or surgery. Contraindication to chronic anticoagulation therapy or heparin Unable or unwilling to consent to investigation and follow-up requirements or inability to comply with planned study procedures. LA anteroposterior diameter ≥ 5.5 cm or indexed LA volume ≥ 50mL/m2 on echo. Recent (last 6 months) event that may impact LV function- myocardial infarction, coronary revascularization, pacemaker or cardiac resynchronization therapy. AF suspected to be due to a reversible cause (e.g. hyperthyroidism, recent surgery) Acute coronary syndrome within 4 weeks as defined by ECG ST segment depression or prominent T-wave inversion and/or positive biomarkers of necrosis (e.g. troponin) in the absence of ST-segment elevation and in an appropriate clinical setting (chest discomfort or angina equivalent). Cardiac surgery, angioplasty, or cerebrovascular accident within 4 weeks prior to enrolment. Life expectancy less than 1 year. Chronic kidney disease stage 4 or 5.  Any of the below cardiac diagnoses:  Hypertrophic obstructive cardiomyopathy Severe valvular disease Restrictive or constrictive cardiomyopathy, including known amyloidosis, sarcoidosis, haemochromatosis Complex congenital heart disease Constrictive pericarditis Severe pulmonary hypertension (RVSP > 60 mmHg), Non-cardiac pulmonary oedema Active myocarditis