Withdrawal of Treatment for Heart Failure Patients With Recovery From Tachycardia-induced Cardiomyopathy

Inclusion Criteria: Patients with new onset heart failure (ambulatory or hospital) with reduced ejection fraction (LVEF≤40% assessed by echocardiography) and NYHA ≥2 and atrial fibrillation or atrial flutter with ventricular rate ≥110 bpm (ECG monitoring, hospital telemetry or Holter monitoring) that following GDMT - while AF is terminated (e.g. ablation or conversion) or controlled (HR\<110 on resting ECG) - experience LVEF remission (LVEF ≥50%), normalization of indexed LV volume, and normal ECG (no bundle branch block, ST segment deviations or T-wave inversion) and NT-proBNP \<250 pg/ml. Exclusion Criteria: * 18 years or older and able to consent * Former ablation procedures and inability to tolerate antiarrhythmic drugs * Pregnancy * Congenital heart disease (congenital defects with no hemodyamic effects are not excluded) * Previously genotyped positive for genes known to cause cardiomyopathy * Probable hypertrophic, restrictive or non-compaction cardiomyopathy * Moderate/severe valvular disease * Suspicion of or known cardiac amyloidosis, sarcoidosis, or other storage/inflammatory disease * More than 10% PVCs or documented sustained ventricular arrhythmias * History of persistent or permanent AF with ventricular rates \>110 before incident HF despite best standard of care * eGFR \< 30 ml/min/1.73 m2 * Acute myocardial infarction at index * Probable medication-, alcohol- or illicit drug use induced AF and/or HF * Systolic blood pressure \>160 mmHg (at multiple measurements) at index or history of uncontrollable hypertension * Myocarditis * Cardiogenic shock at index * Aborted sudden cardiac death * Pacing-induced cardiomyopathy * 1.st degree relative with DCM