QT Changes as Detected From LINQ ECG During Antiarrhythmic Loading (LINQ QT)

Inclusion Criteria: * Patients implanted with LINQ/LINQII prior to the study enrollment (no more than 50% patients implanted with LINQII), but no greater than 2.5 years for LINQ or 3.5 years for LINQII, or patients who are indicated to receive a LINQ/LINQII implant at least 7 days prior to antiarrhythmic drug loading * Patients who are scheduled to receive antiarrhythmic drug loading * Age 18-80 * Patient is willing and able to comply with the protocol, including follow-up visits, and performing Holter recordings and patient activation transmissions Exclusion Criteria: * Patients who have a contraindication to long-term antiarrhythmic therapy * Patients not suitable for long-term antiarrhythmic therapy * Patients with a previous, existing cardiac implantation (i.e., cardiac pacemaker or cardiac resynchronization requiring \> 40% pacing, implantable cardioverter defibrillator (ICDs)) * Patients with permanent and persistent AF * Co-enrollment in another study or planning to participate in a concurrent device study during the course of this clinical study that could confound the results