This prospective multi-center randomized controlled study aims to compare atrial fibrillation detection and inappropriate therapy according to activation of atrial sensing capability in patients with implantable cardioverter defibrillator.

Implantable cardioverter defibrillators(ICD) therapy has been shown to reduce sudden cardiac death and improve survival in cardiac arrest survivors as well as in heart failure patients with left ventricular dysfunction.

Atrial fibrillation (AF) is commonly found in ICD implantation patients up to 50%. AF is an independent predictor of mortality, inappropriate shock, and embolic events. Therefore, early detection of AF in patients with ICD is essential for improving the quality of life and overall prognosis of the patients.

Conventional ICDs consist of a single chamber (SC) ICD with a lead only in the right ventricle (RV) and dual chamber (DC) ICD with each lead in the right atrium (RA) and RV. SC ICD has the advantage of shorter procedure time, lower cost compared to DC ICD. In contrast, DC ICD has the advantage of being able to monitor atrial arrhythmic events, but complication rates were higher and additional cost and longer procedure time are usually required than SC ICD. Sixty percent of ICD implantation patients who have are SC ICD Recently, a unique ICD lead with atrial sensing ring capable of monitoring the atrial electrical signals has been developed [Intica 7 VR-T DX ICD (Biotronik., Germany)]. Therefore, turning off the atrial sensing function makes it functionally the same as SC ICD whereas turning on makes it function similar to DC ICD without additional cost and procedure time.

Therefore, Detection of AF could be made earlier with VDD ICD versus conventional SC ICD without atrial sensing capability, providing a better chance to improve the prognosis of ICD patients. However, no study exists which shows whether VDD ICD is better for detecting atrial tachyarrhythmia than conventional SC ICD. Therefore, we designed a multicenter prospective randomized study comparing the AF diagnostic efficacy of VDD ICD (with atrial sensing 'ON') against conventional SC ICD. As the second phase, we also plan to compare inappropriate therapy rate according to atrial sensing status of VDD ICD.

Inclusion Criteria:

1. age ≥ 19 years
2. indication for ICD implantation according to guidelines
3. atrial fibrillation didn't detect by electrocardiogram or Holter test within the past 1 year from the ICD implantation, and
4. CHA2DS2VASc score ≥1 point in male or ≥ 2 in female

Exclusion Criteria:

1. persistent or permanent atrial fibrillation (AF)
2. atrial fibrillation detected by electrocardiogram or Holter test within the past 1 year from the ICD implantation
3. history of the catheter or surgical ablation of AF or taking antiarrhythmic drug
4. scheduled to undergo heart transplant within 1 year
5. life expectancy < 1 year
6. requiring atrial pacing