Remote monitoring is now universally available for all cardiac implantable electronic devices (CIEDs), and it has become the standard of care for the management of patients with these devices. In many countries, it is being proven that patients with implantable defibrillator (ICD) or cardiac resynchronizing therapy (CRT) can benefit from remote monitoring (RM) both economically and clinically. From previous RM related clinical studies, it is reasonably accepted that hospitalization cost and mortality rate is comparably higher in defibrillator patients compared to pacemaker indicated patients.

However, it is yet to be discovered which group of defibrillator patients are the most beneficiaries using remote monitoring system. In this study, the investigators would further categorize defibrillator patients into different indication subgroups and compare both economic and clinical benefits among different indication. By comparing economic and clinical benefits of remote monitoring by different subgroups, the investigators might be able to set a guideline on which group of patients should be strongly suggested for remote monitoring utilization.

Therefore, the investigators perform a prospective study in Korean population to compare economic and clinical benefits of RM compared to conventional follow-up in overall study cohort and by different subgroups. (ICD & CRT-D).

The investigators propose to prospectively recruit 556 patients with ICD or CRT-D implantation in 10 sites in Korea.

• Eligible patients should be enrolled in remote monitoring system 0 to 45 days after successful device implantation and then randomly assigned in a 1:1 ratio to the RM or conventional follow-up group.
• In the RM follow-up arm, the patients are not mandated to visit the clinic unless there is unscheduled call due to adverse event notification.
• In the conventional follow-up arm, the patients should be seen at the clinic according to each center's custom but no longer than 1 year between each visit. Follow-up should be continued accordingly until two-years of device implant.

Inclusion Criteria:

1. All ICD and CRT-D patients who are over the age of 18
2. Ability to provide informed consent and to complete the study and required follow-up

Exclusion Criteria:

1. Those who refuse to participate in the trial.
2. Those who refuse to use remote monitoring system or who live in an environment where remote monitoring system cannot be utilized.
3. Patient who refuse to use or expected to use less than 75% of remote monitoring system.