 This randomized controlled trial RCT will examine a case management program for 320 male and female patients suffering from coronary heart disease with multimorbidity in Mannheim, Germany. The main objectives are to evaluate how case management and social interaction alone compared to standard medical care affect the primary and secondary outcomes: physical health, quality of life, loneliness, depression, self-efficacy, outcome expectancies, social support, health locus of control, lifestyle behavior, social network, vulnerability, intention, severity, health worries and cognitive functions. 