Vice President Richard B. Cheney's heart condition may adversely affect his job performance, said professors from the Harvard Medical School (HMS) and Kennedy School of Government.

Cheney, 60, recently released after being hospitalized for heart trouble, has a history of coronary disease.

He suffered the first of four heart attacks at age 37 and experienced his most recent in November, when a mild attack briefly sidelined Cheney during the dispute following the presidential election.

And on Monday, Cheney checked into George Washington University Hospital reporting chest pains.

Doctors found that scar tissue had developed around the artery support structure, known as a stent, used in the November angioplasty, and blockage in the artery had returned to 90 percent of its original severity.

Eugene Braunwald, a professor at HMS, said the problem could return.

"This [latest incident has] about a 40 percent chance of declaring itself again," Braunwald said.

And Braunwald said the severity of Monday's problem has been downplayed by the White House.