David Letterman was joking in his New York hospital room yesterday as he recovered from emergency quintuple bypass surgery Friday after an angiogram showed one of his arteries was severely constricted.

"I feel fantastic. In addition to rerouting the arteries, they also installed an E-Z Pass," the Associated Press quoted the 52-year-old, late-night television host as saying as he joked about commuter toll passes.

In a bypass operation, a surgeon reroutes the flow of blood around narrowed sections of the coronary arteries, the two blood vessels delivering oxygen-rich blood to the beating heart muscle.

This can be achieved two ways.

A healthy artery that delivers blood to the breast can be moved several inches and stitched onto a coronary artery below the narrowed area, augmenting the diseased vessel's "downstream" blood flow. In the second method, a large vein is removed from the leg and cut into pieces several inches long. One end of a piece is then sewn to a coronary artery above a blockage, and the other end sewn to the same artery below the blockage. This gives blood a way to "bypass" the narrowed area.

"Dave's doing great," AP quoted O. Wayne Isom, chairman of cardiothoracic surgery at the Weill Cornell Center of New York-Presbyterian Hospital, as saying. "He's on his way to a full recovery."