RESUMO
The Kansas City Cardiomyopathy Questionnaire-12 (KCCQ-12) is a simple, feasible, and sensitive questionnaire developed in English for assessing the health status (symptoms, function, and quality of life) of patients with heart failure (HF). We aimed to assess the internal consistency and construct validity of the Portuguese version of KCCQ-12. We administered the KCCQ-12, the Minnesota Living Heart Failure (MLHFQ), and the New York Heart Association (NYHA) classification by telephone. Internal consistency was assessed with Cronbach's Alpha (α-Cronbach) and construct validity with correlations to the MLHFQ and NYHA. Internal consistency was high (α-Cronbach = 0.92 for the Overall Summary score and 0.77-0.85 for the subdomains). Construct validity was supported by finding high correlations between the KCCQ-12 Physical Limitation and the Symptom Frequency domains with the physical domain of the MLHFQ (r = -0.70 and r = -0.76, p < 0.001 for both) and the Overall Summary scale with NYHA classifications (r = -0.72, p < 0.001). The Portuguese version of KCCQ-12 has high internal consistency and shows a convergent construct validity with other measures quantifying the health status of patients with chronic HF and can be used confidently in Brazil for research and clinical care.