CASTLE-HFpEF (Catheter Ablation for Atrial Fibrillation Patients With Heart Failure With Mildly Reduced and Preserved Ejection Fraction)

Heart failure with preserved ejection fraction (HFpEF) is highly prevalent and often coexists with atrial fibrillation (AF), but the optimal management strategy for AF in this population remains unclear. The CASTLE-HFpEF (CASTLE-AF II) trial is a prospective, randomized, multicenter study designed to evaluate whether catheter ablation of AF improves clinical outcomes compared with optimized medical therapy in patients with HFpEF.

Approximately 4,000 patients with HFpEF will undergo AF screening using an insertable cardiac monitor. Of these, 980 patients with newly diagnosed AF or AF detected during screening and with an AF burden > 1% will be randomized 1:1 to catheter ablation or guideline-directed medical therapy. All randomized patients will be followed for three years and monitored continuously for AF burden.

The primary endpoint is a hierarchical composite including all-cause mortality, stroke or transient ischemic attack, hospitalization for worsening heart failure, and a clinically meaningful reduction in N-terminal pro-B-type natriuretic peptide (NT-proBNP) at 12 months. Secondary endpoints include total heart failure events, patient-reported quality-of-life outcomes, AF burden and rhythm control metrics, and echocardiographic measures of cardiac structure and function.

This study seeks to determine whether AF ablation improves clinical outcomes and quality of life in patients with HFpEF and AF, and to define the role of rhythm control strategies in this population.

Inclusion criteria

• ≥18 years of age at screening visit.
• Clinical signs and symptoms of HF (26).
• Left ventricular ejection fraction (LVEF) >40% within the past 12 months (most recent LVEF measurement)
• Elevated NT-proBNP levels during screening or within 12 months prior to screening (most recent value; blood test):

• For patients in normal sinus rhythm (NSR) at the time of blood sampling: NT proBNP ≥300 pg/mL
• For patients in AF at the time of blood sampling: NT-proBNP ≥600 pg/mL
• Echocardiographic evidence of HFmrEF/HFpEF, with at least one of the following during screening or within the 12 months prior to screening:

• Left atrial volume index (LAVI) ≥34 mL/m2 for patients in NSR, or LAVI ≥40 mL/m2 for patients in AF.
• Tricuspid regurgitation (TR) peak velocity >2.8 m/s.
• Mitral E/e' ratio at rest ≥9.
• Left ventricular mass index (LVMI) ≥115 g/m2 for men and ≥95 g/m2 for women.
• Septal thickness or posterior wall thickness ≥1.1 cm.
• Patients previously diagnosed with persistent AF since ≤4 months prior to screening with an indication for anticoagulation, OR Patients previously diagnosed with paroxysmal AF since ≤4 months prior to screening with an already known AF burden of ≥1% and/or an AF episode of ≥24 hours, with an indication for anticoagulation OR Patients with paroxysmal AF without known AF burden (diagnosed since ≤4 months prior to screening) or no previously diagnosed AF who are subsequently diagnosed with AF after receiving a single-lead electrocardiography (ECG) patch for 30 days. These patients should have an AF burden of ≥1% and/or an AF episode of ≥24 hours on the ECG patch (more details down below in section 8.1.1) and an indication for anticoagulation.
• Stable optimal medical therapy for HFmrEF/HFpEF for at least 4 weeks (diuretics & SGLT2 inhibitors unless contraindicated; angiotensin receptor-neprilysin inhibitors & mineralocorticoid receptor antagonists as deemed appropriate by the treating physician; Amiodarone and Beta-blockers are not considered for defining heart failure therapy).
• Signed written informed consent obtained from the participant or participant's legal representative and ability for participant to comply with the requirements of the study.

Exclusion criteria

• Participants will be excluded from the study for any of the following reasons:

• Previous catheter ablation for AF.
• Known infiltrative cardiomyopathy, hypertrophic cardiomyopathy and amyloidosis.
• Documented left atrial diameter >6cm.
• Any contraindication for chronic anticoagulation therapy or heparin, including hypersensitivity to any of the components.
• Acute coronary syndrome, cardiac surgery, angioplasty, or cerebrovascular accident within 2 months prior to enrollment.
• Planned cardiovascular intervention during the follow-up period.
• Patients with severe valvular disease
• Life expectancy ≤12 months.
• Untreated hypothyroidism or hyperthyroidism (blood test).
• Requirement for dialysis due to end-stage chronic kidney disease.
• Mental or physical inability to participate in the study.
• Women currently pregnant (blood test) or breastfeeding or not using reliable contraceptive measures during fertility age.
• Enrollment in another investigational drug or device study within the last 30 days before registration.
• Medical or psychological conditions that would not permit the participant to complete the study or sign informed consent.
• Known alcohol or drug abuse.
• Presence of a condition, abnormality or disease that in the opinion of the investigator would compromise the safety of the participant or the quality of the data.
• Legal incapacity or limited legal capacity.