RT Journal Article SR Electronic T1 Early detection of left ventricular dysfunction in patients with β thalassaemia major by dobutamine stress echocardiography JF Heart JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP 669 OP 670 DO 10.1136/heart.89.6.669 VO 89 IS 6 A1 L Hui A1 M P Leung A1 S Y Ha A1 A K T Chau A1 Y F Cheung YR 2003 UL http://heart.bmj.com/content/89/6/669.abstract AB