(CNN)-- Preliminary findings from the medical examiner indicate 'aortic dissection', or a tear in the aorta, for the late U.S. Senator Lindsey Graham, which is associated with cardiovascular disease.

CNN medical analyst Dr. Jonathan Reiner explained what happened, saying: 'The heart delivers blood to the body through a very large artery called the aorta. Imagine a blood vessel about twice the diameter of a garden hose, and under immense pressure,' adding: 'The pressure in the aorta is the pressure a doctor measures with a blood pressure cuff. So it is under great pressure.'

He continued: 'The aorta is a blood vessel composed of three layers, and the inner layer is called the intima. Aortic dissection occurs due to a tear in this intima, allowing blood to leak into the arterial wall. When that happens, many serious complications can occur.'

He also noted that 'when blood flows into the arterial wall, it can compress the channel that carries blood to the body, leading to reduced blood flow to the heart, brain, and major abdominal organs.'

He added: 'Another thing that can happen with aortic dissection is that it can also rupture. In that case, this large artery, under high pressure, can pump a massive amount of blood into the chest in a very short time. When that happens, the injury is usually fatal. However, if the artery dissects without rupturing, there is a relatively brief window to save the patient.'