Sen. Lindsey Graham (R-S.C.) died Saturday night at his Washington, D.C. home at age 71, after what his office initially described only as a “brief and sudden illness.” On Sunday, his office released preliminary findings from the District of Columbia’s chief medical examiner: aortic dissection due to arteriosclerotic cardiovascular disease. Emergency medical services had responded to a call for cardiac arrest at the senator’s home. The final death certificate remains pending until toxicology and microscopic testing are complete.

Graham had just returned from his 10th wartime trip to Ukraine, and his staff reported no indication that he was feeling unwell. That combination—apparently fine one moment, in cardiac arrest hours later—is exactly how aortic dissection can unfold. As an ER doctor, it is a diagnosis I think about regularly when I see patients. It can kill within minutes and can masquerade as far more common problems. Here is what the preliminary finding means.

What Is An Aortic Dissection?

The aorta is the body’s main artery, a garden-hose-sized vessel that carries blood out of the heart to every organ. Its wall has three layers. A dissection begins when the innermost layer tears, allowing high-pressure blood to surge into the wall itself and split the layers apart. This creates a false channel where blood flows.

Doctors classify dissections by location. Type A dissections involve the ascending aorta, the segment closest to the heart, and are surgical emergencies. Type B dissections are........

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