Background Congenital heart defects (CHD) are common in patients with Down's syndrome; however, patients living in residential centres have not always been screened for CHD in the past. The aim of this study was to investigate the prevalence of CHD in patients with Down's syndrome living in residential centres, and to determine whether cardiac screening should be recommended.

Methods Between January 2007 and November 2009 Dutch residential centres nationwide were randomly sampled. Medical files of all patients with Down's syndrome were investigated to retrieve documented information on known CHD. Echocardiography was performed on patients with unknown cardiac status. The main outcome measure was the number of newly diagnosed cases of CHD in adult patients with Down's syndrome.

Results Thirty-one centres and 1158 patients were included in the first stage of the study. Overall prevalence of known CHD was 16% (189 defects). Screening was performed in 138 patients without known CHD. In total, 24 new patients (17%) with a CHD were found, of which six patients needed semi-urgent care. Furthermore, 77% of the screened patients had mild to moderate regurgitation in one or more heart valves. Overall prevalence of CHD in adult Down's syndrome patients living in residential centres would be estimated at 33%.

Conclusions Seventeen per cent of patients with Down's syndrome living in residential centres had undiagnosed CHD, and valvular regurgitation was present in the majority of patients. Cardiac screening is recommended in older Down's syndrome patients, for whom new therapeutic options are available and for prevention of cardiac complications in old age.