A Case of Success: Guidelines-Based Treatment to Control Atrial Fibrillation-Induced Cardiomyopathy—Atrioventricular Node Ablation and Cardiac Resynchronization Therapy to the Rescue

<b>Background and Clinical Significance</b>: Heart failure with reduced ejection fraction (HFrEF) and atrial fibrillation (AF) frequently coexist, creating a complex clinical interplay that exacerbates morbidity and mortality. AF can directly precipitate or worsen HFrEF through mechanisms such as tachycardia-induced cardiomyopathy, loss of atrial contribution to ventricular filling, and irregular ventricular response. The use of evidence-based therapies improves clinical outcomes in patients with HFrEF. <b>Case Presentation</b>: We present a clinical case of a 58-year-old man with left bundle branch block (LBBB), tachysystolic AF, and the aforementioned induced HFrEF. The patient's medical treatment was optimized according to recent guidelines. Subsequent to the improvements in HF treatment, the patient's echocardiographic data showed a higher left ventricle ejection fraction (LVEF); however, it remained below 35%. Moreover, tachysystolia persisted and was not sufficiently controlled with medications. Therefore, an upgrade of the pacemaker to cardiac resynchronization therapy (CRT) following the destruction of the AV node was performed to control tachysystolic AF and worsening of HF. After the treatment adjustments, the patient's symptoms regressed, and echocardiography showed improved LVEF up to 41%. <b>Conclusions</b>: This case highlights the successful identification and timely application of intensive heart rate control management and heart failure induced by AF treatment.