Complex sentence: Esselstyn received his M.D. from the Case Western Reserve University School of Medicine in 1961 (during which time he met his wife Ann), and was an Intern (1961--62) and Resident (1962--66) at the Cleveland Clinic.
Split into simpler sentences: Esselstyn received his M.D. from the Case Western Reserve University School of Medicine in 1961 (during which time he met his wife Ann). He was an intern (1961--62) and resident (1962--66) at the Cleveland Clinic.