Lindsey Graham Cause of Death: US Senator Lindsey Graham, President Donald Trump’s critic turned ally, died after a rupture in his aorta, news agency AP reported, citing a preliminary medical examiner's finding shared by his office. The rupture was related to the hardening of Graham's arteries. However, the official cause of death will be disclosed after toxicological and microscopic testing.The latest update comes hours after his office had initially said he had suffered from a "brief and sudden illness." Graham, a prominent South Carolina Republican and former Air Force lawyer who served in Congress for more than three decades, had turned 71 years old just two days before dying on Saturday night. His office had originally saidTrump said on NBC's "Meet the Press" that Graham had called him on Saturday night after returning from a trip to Ukraine and "sounded a little bit tired, but perfect." The president ordered that flags across the country be flown at half-staff until next Saturday evening.Elected to the Senate in 2002 after serving in the House, Graham long championed robust U.S. military interventionism and a strong national defense, positions that later clashed with the rising isolationist wing of his party, even as he became well-known for his close ties with Trump, whom he briefly opposed in the 2016 presidential nomination race and had called him “unfit for office.”What is aortic dissection?Aortic dissection is a tear in the inner layer of a weak area of the aorta, where blood entering the tear forces the layers of the aorta apart, according to Cleveland Clinic and Mayo Clinic. The aorta, the body’s main artery carrying oxygen-rich blood, can develop a dangerous tear known as an aortic dissection, a life‑threatening emergency that demands immediate medical attention, typically managed through a combination of surgical procedures and medication.ALSO READ: Lindsey Graham dies at 71: What we know about the pivotal Republican senator and Trump critic-turned-ally's cause of death