Many people suffer DVT after spending long periods without moving,such as passengers on long-haul airline flights. Cheney spent about 65hours on a plane on a nine-day, round-the-world trip that ended lastweek.
''When you're just sitting there with your legs hanging downfor long periods of time, that's what predisposes you to the problem,''said Sean O'Donnell, chief of vascular surgery of Washington HospitalCenter.
''Treated properly, it poses a small threat,'' O'Donnell said. ''Untreated and unrecognized, it's a very serious problem.''