Patient population: Registry population consists of CHD patients with tachyarrhythmia's, defined as atrial fibrillation (AF) or atrial tachycardia's (AT), including atrial flutter, on NOACs. Patients with new-onset atrial tachyarrhythmia's who are eligible for NOACs, will be started directly on a NOAC. Patients on vitamin K antagonists (VKA) can be switched actively to NOACs during outpatient clinic visits, in case of agreement of both patient and physician. The switch can be initiated for various reasons, including bleeding complications on VKA, unstable INR measurements, and user friendliness. Eligibility for NOAC use is defined conform clinical practice, i.e. a patient with nonvalvular atrial tachyarrhythmia's, but without a mechanical heart valve, significantly elevated risk of bleeding, impaired renal function, or pregnancy.