Doctors are evaluating Dick Cheney after the former vice president experienced chest pains and was sent to George Washington University, where doctors reportedly gave him an angiogram to examine his coronary arteries. Cheney is "stable" and "resting comfortably," according to doctors and family members quoted by NBC News, but may need additional treatment tomorrow.

Cheney has had four heart attacks and in 2001 has an electrical device implanted after he was found to have an unsteady heartbeat.