This is a non-interventional/observational study designed as a retrospective chart review. Study sites will identify patient charts within their existing databases in a fair and consistent manner, e.g., reviewing all eligible charts in reverse chronological order by year of baseline visit. Patients meeting the eligibility criteria who have a minimum of 5 years of follow-up data since the implantation of the P-50 or P-200 device will be enrolled, including patients whose 5-year standard of care visit is scheduled during the study enrollment period.
The overall study duration is expected to be approximately 7 months.
