1Division of Cardiovascular Medicine, University of Iowa Hospitals and Clinics, 200 Hawkins Dr, 4434 JCP, Iowa City, IA 52242, USA and
2Department of Cardiothoracic Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
*Corresponding author. Tel: þ1 301 641 6062; fax: þ1 319 338 5263,
Received 23 November 2009; accepted after revision 4 February 2010