Abstract: Background
There is a lack of German-language, disease-specific health related quality of life instruments applicable in cardiac rehabilitation. The purpose of this project was to investigate the psychometric properties of the German version of the MacNew Heart Disease Health-related Quality of Life Questionnaire (MacNew) in patients undergoing cardiac rehabilitation.

Methods
The MacNew was filled out by 5692 inpatients. We analysed acceptance (number of missing values), ceiling and floor effects, reliability (Cronbach’s α), factor structure (confirmatory factor analysis), construct validity (correlation with a generic health-related quality of life instrument), and sensitivity to change.

Results
Two items had more than 7% missing data. We observed neither floor nor ceiling effects. Cronbach’s α of the scales ranged from 0.78 (physical scale) to 0.95 (global scale). Confirmatory factor analysis failed to reproduce the proposed factor structure (CFI = 0.882; TLI = 0.871; RMSEA = 0.074). We therefore drafted our own model (CFI = 0.932; TLI = 0.921; RMSEA = 0.064), and observed a correlation pattern largely conforming to the hypotheses with a generic health-related quality of life instrument. The effect sizes we noted between the start and end of rehabilitation fell between 0.66 and 0.74; at the 6-month follow-up they ranged from 0.69 to 0.92.

Conclusions
The German version of the MacNew Heart Disease Health-related Quality of Life Questionnaire is a suitable instrument with which to measure the impairment experienced by individuals with heart disease during inpatient cardiologic rehabilitation. The social and the global scale must be interpreted cautiously