Dear Doctors: I get a cramp in my left calf when I run for more than 20 minutes. When I slow down, it goes away. I told my doctor about it, and she wants to do something called an ankle brachial index. What will it entail? I think it’s a heart test. What does my calf have to do with my heart?
Dear Reader: Your doctor has recommended you undergo an ankle brachial index test because she suspects the calf pain you are experiencing when you exert yourself may signal a condition called peripheral artery disease. Also known as PAD, it occurs when the arteries that deliver blood to the limbs become narrow. It can affect either the arms or the legs but occurs more often in the blood vessels in the legs.
A common cause of PAD is atherosclerosis, which is a buildup of plaque in the artery walls. Other risk factors include high blood pressure, unhealthy blood lipid values, diabetes and a history of tobacco use.
Narrowed arteries impede the flow of blood, and, thus, of oxygen and nutrients to the affected tissues. When the narrowing is minor, symptoms may not appear. But when the demand for oxygen and nutrients rises, as happens when you exercise, the decreased flow of blood can lead to the cramping pain you described. A muscle pain that eases when you slow your exertion is also something that occurs in PAD.
Diagnosis of the condition typically begins with a physical exam and a review of your medical history. It also includes the ankle brachial index test you have been asked to undergo. This is a noninvasive and painless test. It is done by measuring the blood pressure in your legs and in your arms and performing a calculation that results in a ratio. When there is narrowing of a peripheral artery that serves one of the limbs, blood pressure in that artery will be affected.
For the test itself, you will be asked to lie down on an examining table and rest for a short time. When the test begins, a specialized inflatable blood pressure cuff will be used to take the blood pressure in each arm. The cuff will also be used to measure the blood pressure in each of your ankles. The technician will also be using a hand-held ultrasound device that produces images and expands the window of time during which the pulse can be heard. When there is significant blockage to an artery, it can be necessary to measure the blood pressure in the big toe.
A calculation of .90 to .99 indicates mild PAD. Numbers lower than that suggest greater obstruction of the affected artery. Results lower than .90 can indicate a need for imaging tests, such as ultrasound or an angiogram. Minor blockage may be addressed with lifestyle changes that include diet and exercises. Medications to reduce blood clotting risk and improve blood lipid numbers may be prescribed. More severe blockages may require surgery. Your doctor will review your test results with you and, based on what they reveal, will recommend treatment.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
