Recent advancements with implantable cardiac device technology include extensive diagnostic and therapeutic algorithms for prevention as well as termination of atrial tachyarrhythmias (ATA). Preventive atrial pacing (PAP) and a novel atrial antitachycardia pacing algorithm (Reactive ATP™) in conjunction with managed ventricular pacing (MVP) recently has been shown to reduce progression to permanent atrial fibrillation (AF) in pacemaker patients with intact atriovenous (AV) conduction and a history of ATA. Whether the use of Reactive ATP™ for reducing AF burden extends to patients with an implantable cardioverter defibrillator (ICD), who typically have structural heart disease and heart hailure (HF), is unknown.

Atrial tachyarrhythmias (ATA) and heart failure (HF), which are well-recognized causes of morbidity and mortality, are growing and concerning issues in our patient population. In patients implanted with a dual-chamber implantable cardioverter defibrillator (ICD), progression of paroxysmal to persistent or permanent atrial fibrillation (AF) has been documented. Because of the untoward consequences of AF, such as development/worsening of HF or thromboembolic events (stroke and myocardial infarction [MI]), prevention of permanent AF has the potential to improve quality of life, reduce hospitalizations, and decrease the complications associated with AF.

Recent advancements with implantable cardiac device technology include extensive diagnostic and therapeutic algorithms for prevention as well as termination of ATA. Preventive atrial pacing (PAP) and a novel atrial antitachycardia pacing algorithm (Reactive ATP™) in conjunction with managed ventricular pacing (MVP) recently has been shown to reduce progression to permanent AF in pacemaker patients with intact atriovenous (AV) conduction and a history of ATA. Results of that study suggested that Reactive ATP™ specifically was responsible for this effect. Whether the use of Reactive ATP™ for reducing AF burden extends to patients with an implantable cardioverter defibrillator (ICD), who typically have structural heart disease and HF, is unknown.

The aim of this study is to evaluate the effectiveness of atrial antitachycardia pacing (Reactive ATP) in patients implanted with either a dual-chamber or cardiac resynchronization therapy (CRT) ICD who have a history of ATA.

Inclusion Criteria:

• male and female patients
• ≥18 years old (no upper age limit)
• previously implanted with a Medtronic dual-chamber or CRT ICD with capability of atrial antitachycardia pacing; specifically, Reactive ATP™ at least 9 months previously (six months data collection and implant occurring at least 3 months previously to allow healing and establishment of stable sensing)
• measured P wave in sinus rhythm of at least 0.8 mV
• >=6 months AT/AF burden data available, either from CareLink® or in-office interrogation
• >=1.0% AT/AF burden (hours in atrial fibrillation/total hours monitored) in the last 6 months
• No change in antiarrhythmic drug therapy (Vaughan-Williams class I or III) in the last 6 months

Exclusion Criteria:

• Persistent or permanent AT/AF (AF burden >95%)
• Cardioversion for atrial fibrillation or atrial flutter within the last 6 months, either intentional or as a result of a tachyarrhythmia therapy
• Ablation for atrial fibrillation or atrial flutter within the last 9 months (6 months data collection following a 3 month blanking period post procedure)
• Reactive ATP™ previously programmed on
• Measured P waves in sinus rhythm consistently <0.8 mV on repeat measurements.
• Unresolved artifactual AT/AF detection due to far-field R wave or other oversensing
• Expected generator change or other device surgery within six months