This proposal details the implementation of an international (Singapore and New Zealand) multi-centre study to test a novel therapeutic strategy aimed at reducing the burden of atrial fibrillation - an important medical condition with major healthcare implications. Unique aspects of this study include i) a non-arrhythmic treatment target (mineralocorticoid receptor antagonism) -targeting the arrhythmogenic substrate of AF before it becomes permanently established, ii) the use of pacemaker monitoring capability to accurately document AF burden, thus increasing the power of the study and iii) multi-national collaborative, double blind design.

Inclusion Criteria:

• Age > 21 years (without child-bearing potential for women);

• With a permanent pacemaker capable of AF monitoring;

• Device documented AF in the last 12 months; Defined as:

  i. atrial high rate events (AHRE) > 220 bpm for >1% of the time; or ii. > 6 mins on at least one occasion

Exclusion Criteria:

• Persistent (defined as sustained AF lasting continuously for 7 or more days)
• History of heart failure with indication for MRAs
• Any existing clinical indication for MRA or K+ sparing diuretic such as uncontrolled hypertension or oedema
• Contraindication to MRA
• Severe renal dysfunction (eGFR <30ml/min by CKD-Epi)
• Sustained hyperkalaemia (defined as K+ >5mmol/L in the absence of reversible cause)
• Receiving AF suppression pacing
• Women of child bearing potential
• Patients taking medications which may interact with the study drug or increase the level of potassium in the blood, include lithium, amiloride, cyclosporine, eplerenone, tacrolimus, and triamterene.