Atrial Fibrillation: Chronic Beta-blocker Use Versus As-needed Rate Control Guided by Implantable Cardiac Monitor

The goal of this study is to test the feasibility of guiding as-needed pharmacological rate control of atrial fibrillation (AF) by implantable cardiac monitors and to assess the impact of continuous beta-blocker therapy versus as-needed rate control on the following outcomes:(1) exercise capacity, (2) AF burden, (3) symptomatic heart failure, (4) biomarker assessment of cardiac filling pressures and cardio-metabolic health, and (5) quality of life in patients with atrial fibrillation and stage II or III heart failure with preserved ejection fraction.

Inclusion Criteria:Paroxysmal or persistent AF diagnosed in the past 4 weeks or longerImplantable cardiac monitor (either loop recorder or pacemaker)Current treatment with greater than minimum doses of beta-blockers OR any beta-blocker with resting sinus rhythm heart rate < 75 bpm (documented on EKG in the last 6 months OR at enrollment visit)Left ventricular ejection fraction ≥ 50% (reported on echocardiogram within the past 48 months)Echocardiographic evidence of structural changes consistent with HFpEF defined by (1) left ventricular hypertrophy (septal or posterior wall thickness > 10mm) OR (2) left atrial enlargement OR (3) diastolic dysfunction.Exclusion Criteria:Long-standing persistent or permanent atrial fibrillation (Long-standing persistent AF is defined as continuous AF of > 12 months duration. Permanent AF is defined as AF accepted by the patient and physician and no further attempts to restore/maintain sinus rhythm will be undertaken).Echocardiographic evidence of left ventricular dilation (defined as left ventricular end diastolic volume (LVEDV) index ≥ 80ml/m2 as determined by echocardiogram within the past 48 months.Documentation in the electronic medical record suggesting a life expectancy less than 12 monthsMinimum dosage of beta-blocker therapy to meet enrollment criterion:Metoprolol tartrate 25mg twice daily, Metoprolol succinate 50mg daily, Carvedilol 12.5mg daily, Bisoprolol 5mg twice daily, Nebivolol 5mg daily, Atenolol 50mg daily, Labetalol 100mg twice daily, Propranolol 40mg twice daily