Mixed-methods process evaluation of the "Karl-Heinz" cardiac prehabilitation program in older patients: protocol for the PRECOVERY trial. - Munderloh A; Steinmetz C; Heinemann S; von Arnim CAF; Asendorf T; Mathes T; Sadlonova M; Sekanina U; Hummers E; Müller CA (Trials, 2026)