1. From the Cardiothoracic Surgery Service, Brooke Army Medical Center, Ft. Sam Houston, Texas, From the Division of Cardiothoracic Surgery and Vascular Surgery, University of Wisconsin School of Medicine, Madison, Wisconsin, Division of Cardiothoracic Surgery, University of Texas Health Science Center, San Antonio, Texas
2. From the Cardiothoracic Surgery Service, Brooke Army Medical Center, Ft. Sam Houston, Texas
3. From the Division of Cardiothoracic Surgery and Vascular Surgery, University of Wisconsin School of Medicine, Madison, Wisconsin