Lindsey Graham, the longtime Republican US senator from South Carolina and a close ally of President Donald Trump, died on Saturday at the age of 71.Senator Lindsey Graham died from aorta rupture. (AFP)According to a preliminary finding from the medical examiner, Lindsey Graham died from an aortic rupture caused by hardened arteries.What is an aortic rupture?An aortic rupture is a life-threatening medical emergency in which the aorta tears or bursts completely.The aorta is the body's largest artery. It carries oxygen-rich blood from the heart to the rest of the body.A rupture can cause severe internal bleeding and can quickly become fatal without immediate treatment.According to Mayo Clinic, aorta rupture is often linked to an aortic aneurysm, a weakened, bulging section of the aorta that can burst.Risk factors include high blood pressure, atherosclerosis, smoking, advanced age, connective tissue disorders, trauma, a family history of aortic disease, and a bicuspid aortic valve. In some cases, sudden physical or emotional stress may trigger a rupture.Common symptoms include sudden, severe "tearing" or ripping pain in the chest, upper back, or abdomen, shortness of breath, loss of consciousness, weakness on one side of the body, and signs of shock such as low blood pressure and a rapid pulse. The condition can sometimes be mistaken for a heart attack.TheoriesAccording to NBC News, emergency personnel responded to a call for "cardiac arrest" at Graham's Capitol Hill home on Saturday night.In a post on X, his office announced his death, saying he died after "a brief and sudden illness."Graham died shortly after returning from a trip to Ukraine. His death sparked online speculation and conspiracy theories about assassination or poisoning. However, officials have said there is no evidence of foul play.Also Read: Why did Lindsey Graham never get married? What late senator revealed, ‘The right girl was smart enough not to…’Trump pays tributePresident Donald Trump paid tribute to Graham, calling him "a true American Patriot."“Senator Lindsey Graham, one of the greatest people and Senators I have ever known, is dead! He was always working, and was a true American Patriot. Lindsey will be greatly missed!!! DETAILS AND ARRANGEMENTS TO FOLLOW. So sad!” Trump posted on Truth Social.Trump later said he had spoken with Graham before his death on Saturday and that the senator "sounded a little tired."“He called and he said, ‘We’re all set for the SAVE America Act.’ He was pushing the SAVE America Act like crazy,” Trump told NBC News’s Kristen Welker on 'Meet the Press.'Trump said Graham had just returned from Ukraine and called him around 7 pm."He sounded a little tired, but perfect, but a little bit tired. [He] had a right to be. Man, he was a worker. He was really a worker."