Efficacy of Aldosterone Antagonist Therapy for Prevention of New Atrial Fibrillation

Inclusion Criteria: * diagnosis of typical AFL confirmed by 12-lead ECG * no documented AF on ECG, ambulatory monitor, pacemaker or ICD at any time * scheduled to undergo catheter ablation of the CTI for treatment of AFL * history of hypertension (HTN) or heart failure (HF) (reduced or preserved systolic function) Exclusion Criteria: * history of known AF episodes * previous CTI or PVI ablation procedure * other SVT mechanisms demonstrated (AVNRT, AVRT or accessory pathways) * amiodarone usage within the past 3 months, * unwillingness to participate or undergo insertable monitor implantation * hyperkalemia (potassium \> 5.0 mEq/L) * severe renal disease (Cr \>2.5 mg/dL \[men\], \>2.0 mg/dL \[women, GFR \< 30 mL/min/1.73 m2) * life expectancy \< 18 months * prior intolerance to treatment with an aldosterone antagonist * current treatment with an aldosterone antagonist * need for treatment with a class I or III AAD for another indication * operative AFL (occurring within 30 days of surgery) that is expected to resolve * presence of a cardiac rhythm device (pacemaker or ICD) capable of AF monitoring * currently pregnant or nursing a child * unwilling not to become pregnant and to use birth control while taking spironolactone