A clnical trIal comparing the effect of treatment with oral spironolactone compared with a placebo on the frequency and duration of atrIal fibrillation in patients with an implanted cardiac device in New Zealand.

INTERVENTION: We will test the ability of the oral mineralocorticoid receptor antagonist (MRA), spironolactone, to prevent Atrial Fibrillation (AF) by performing a randomised controlled clinical trial and using monitoring features of implanted pacemakers to accurately document AF. Participants will be randomised 1:1 to receive either placebo or spironolactone 50mg per day for 18 months. The dose of the study drug will be adjusted by the study doctor every 3 months during the 18 month intervention period according to renal function (eGFR) and potassium (K+) biochemistry levels. . The starting drug dose will be 25mg/d, titrated to 50mg/d after 4 weeks if K+ is <5mmol/L If the baseline eGFR is 30‐50ml/min/1.73m2, the starting dose will be 25mg on alternate days and titrated to 25mg daily at 4 weeks if K+ <5mmol/L The dose will be halved if K+ increases into the range 5.5 ‐ 6mmol/L or eGFR falls <15ml/min/1.73m2. Following dose reduction, blood tests will be repeated K+ / eGFR in 72hrs and doses continued if K+ <5 and eGFR >30ml/min/1.73m2 Study drug withheld if K+>6mmol/L, restart at half dose only if K+<5mmol/L at 72hrs Study drug withheld if eGFR <15ml/min/1.73m2 and restarted once eGFR > 30ml/min/1.73m2 Medications will be counted as a check on adherence at all study visits. CONDITION: Atrial Fibrillation PRIMARY OUTCOME: This is a composite primary outcome to determine the effect of MRA treatment on echocardiographic measures of left atrial remodeling including atrial size and mechanical function To determine the effect of MRA treatment on biological markers of cardiac loading from blood sample. e.g., BNP/NT‐proBNP, aldosterone, plasma renin activity, angiotensin‐II.. Total burden (frequency and duration) of episodic AF assessed by uploaded pacemaker monitoring records, SECONDARY OUTCOME: Hyperkalaemia Renal function by eGFR from serum samples. INCLUSION CRITERIA: Patients with an implanted cardiac device capable of recording the frequency and duration of AF events and with evidence of AF or AHRE within the 6months prior to recruitment will be eligible. INCLUSION CRITERIA: age >18 years (without childbearing potential for women); with an implantable device capable of AF or AHRE monitoring; and with device documented AF or AHRE (defined as AHRE >220 bpm for >2% of the time or for > 5mins on at least one occasion) in the last 6months.