'cardiac-related' is a modern compound formed from English 'cardiac' + 'related'. 'Cardiac' ultimately comes from Greek 'kardia' meaning 'heart', and 'related' comes via Old French/Latin from Latin 'relatus' (past participle of 'referre') meaning 'brought back' or 'connected'.

'cardiac' entered English via Late Latin 'cardiacus' (from Greek 'kardiakos') and French 'cardiaque'; 'related' comes from Latin 'referre' → past participle 'relatus' → Old French 'relater' → English 'relate'. The compound 'cardiac-related' is a recent English formation (20th century onward) using the adjective 'cardiac' plus the participial adjective 'related'.

Originally elements meant 'of the heart' (cardiac) and 'connected/brought back' (related); together they now mean 'connected with or caused by the heart'.