Cardiac dysfunction in mixed connective tissue disease: a nationwide observational study.

"for a full description of the echocardiographic protocol please see supplementary data s1."

"Declarations Conflict of interestSimon Girmai Berger, Birgit Nomeland Witczak, Silje Reiseter, Thomas Schwartz, Helena Andersson, Siri Opsahl Hetlevik, Kristin Schjander Berntsen, Helga Sanner, Vibke Lilleby, Ragnar Gunnarsson, Øyvind Molberg, Ivar Sjaastad and Mathis Korseberg Stokke declare that they have no conflict of interest. Ethical approvalAll procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Regional Committee for Medical and Health Research Ethics (REC) in Norway (REC South East 2012/1432, 2013/1039, 2012/1721 and 2011/895). Consent to participateAll patients and controls signed written informed consent forms to participate in the study. Consent to publicationWritten informed consent for publication was obtained from all patients and controls. Conflict of interest Simon Girmai Berger, Birgit Nomeland Witczak, Silje Reiseter, Thomas Schwartz, Helena Andersson, Siri Opsahl Hetlevik, Kristin Schjander Berntsen, Helga Sanner, Vibke Lilleby, Ragnar Gunnarsson, Øyvind Molberg, Ivar Sjaastad and Mathis Korseberg Stokke declare that they have no conflict of interest."

"Funding Open access funding provided by University of Oslo (incl Oslo University Hospital). This work was supported by the Research Council of Norway. Norges Forskningsråd."