Is Bay Ridge Avenue the same as Bay Ridge Blvd? If so, is it close to Lutheran Medical Center?

There's no such a street as Bay Ridge Boulevard. It's known as "Ridge Boulevard". Bay Ridge Avenue is also known as 69th Street to locals. (And Bay Ridge Parkway is known as 75th Street). If you're walking along Ridge Boulevard to go to Lutheran Medical Center (55th Street), Ridge Boulevard will become Second Avenue. Depending on what time of day you are walking, it's not very commercialized, so it could be a bit dodgy at night.

bay ridge avenue and bay ridge blvd are two different streets
lutheran is located at 53st on R train so it is closer to bay ridge avenue which is a few streets away from bay ridge blvd