MyChart is just a window that allows you to see your legal medical record at your healthcare organisation. Epic does not store any of your medical information. Your information is always with your healthcare organisation, and there are laws and regulations for them to keep it.
You can deactivate your MyChart account in Account Settings in the MyChart mobile app or by contacting your healthcare organisation's MyChart help desk. You can find their contact information on their FAQ page, which is linked on the bottom of their MyChart website.
When you deactivate your MyChart account, you lose access and stop receiving communications to log in to MyChart. Your medical information is not deleted. Contact your healthcare organisation to reactivate your account.
Deactivate your MyChart account from Account Settings on the website or mobile app. You can also contact your healthcare organisation's MyChart help desk to deactivate.