[1] Hokkaido Univ, Fac Med, Dept Cardiovasc Med, Kita Ku, Kita 15 Nishi 7, Sapporo, Hokkaido, Japan
[2] Hokkaido Univ, Grad Sch Med, Kita Ku, Kita 15 Nishi 7, Sapporo, Hokkaido, Japan
[3] Imperial Coll London, Natl Heart & Lung Inst, London, England
[4] Hlth Sci Univ Hokkaido, Dept Cardiovasc Med, Tobetsu, Japan
[5] Hokkaido Univ Hosp, Div Lab & Transfus Med, Sapporo, Hokkaido, Japan
[6] Hokkaido Univ Hosp, Diagnost Ctr Sonog, Sapporo, Hokkaido, Japan