 Dangerfield experienced a small heart attack while performing stand-up on The Tonight Show on November 22, 2001, his 80th birthday. Host Jay Leno sensed something wasn't right with Dangerfield's movements while he was performing and urged his producer to summon the paramedics. It was determined that in order to enhance blood flow to his brain and prepare for future heart valve replacement operations, Dangerfield needed brain surgery, which was a success. Then the heart operation was performed on August 24, 2004. When asked how long he would stay in the hospital upon entering the University of California Los Angeles Medical Center, he responded with another one of his catchphrases, If all goes well, approximately a week, if not, approximately 1.5 hours. Just six weeks later, on October 5, 2004, at the age of 82, he would pass away due to complications from the surgery.