[1] Kuopio Univ Hosp, Ctr Heart, Kuopio 70211, Finland
[2] Univ Eastern Finland, Fac Hlth Sci, Kuopio, Finland
[3] Univ Ottawa, Inst Heart, Div Cardiac Surg, Ottawa, ON, Canada
[4] Univ Uppsala Hosp, Dept Cardiothorac Surg, Uppsala, Sweden
[5] North Karelia Cent Hosp, Dept Surg, Joensuu, Finland