Harvard Heart Letter

Ask the doctor: Why is my blood pressure higher in one arm than the other?

Ask the doctor

Why is my blood pressure higher in one arm than the other?

Q. I was recently admitted to the hospital in the middle of the night with chest pain. When the doctors took my blood pressure, they found that it was much lower in my right arm than in my left. They rushed me in for a CT scan, saying they were looking for a "tear." Fortunately, there wasn't one, and the next day I underwent angioplasty. What was this tear they were worried about?

A. Your doctors were worried that you might have a rip, or dissection, of your aorta, the large artery that distributes oxygenated blood from the heart to the rest of the body. A tear in the inner layer of the aorta allows blood to pulse between the layers of the aorta's wall. This can cause branches of the aorta to get blocked off. One sign of aortic dissection is a difference in blood pressure readings from one side of the body to the other. This is a potentially life-threatening condition, so your doctors were wise to do the CT scan.

What else might account for the blood pressure difference from one arm to the other? Atherosclerosis is probably partly blocking the main artery carrying blood to the arm with the lower pressure. This is much the same thing that happened in your coronary artery and led to your chest pain and angioplasty. From now on, be sure to do all you can to fight against atherosclerosis so that this problem does not progress in your arm or your heart. And tell the doctors and nurses taking your blood pressure that they can expect a lower pressure in your right arm.

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