Peripheral arterial disease and ulcers: Clinical sciences

Peripheral arterial disease, also known as PAD, is when an extremity, typically the lower limb, does not receive enough blood supply to meet the needs of its tissues. It’s often caused by chronic narrowing of the artery’s luminal diameter, simply known as stenosis, due to atherosclerosis, inflammation, or trauma. Over time, the stenosis decreases the blood supply to the tissue, which can lead to the formation of ischemic ulcers at distal zones of the affected arteries, like the toes.

A more severe form of PAD is called chronic limb-threatening ischemia, or CLTI for short. Keep in mind that CLTI is sometimes called critical limb ischemia, so if you hear that name, don’t be confused.

Alright, your first step in assessing a patient with a chief concern suggesting PAD or an ulcer is to perform a focused history and physical exam. On history, patients typically report intermittent claudication, which is a crampy pain in the calves when walking, and sometimes even pain at rest if the patient progresses to CTLI. You can expect patients to have some underlying comorbidities or risk factors, such as a history of smoking, hypertension, diabetes mellitus, hyperlipidemia, or chronic kidney disease.

Common physical exam findings include cool lower extremities with trophic changes like hair loss, as well as absent or reduced distal pulses, and abnormal capillary refill.

An important part of performing a vascular physical exam is to thoroughly assess for pulses. If you’re unable to palpate a pulse, use a handheld Doppler to listen for a signal. Sometimes you might hear Doppler signals for a pulse that’s not palpable. Make sure to examine proximal vessels like the femoral or popliteal arteries, as well as distal vessels, such as the anterior or posterior tibial arteries. When examining vessels, don’t forget to compare them bilaterally. Next, if you auscultate the femoral artery, you might hear a bruit, which is a sign of a turbulent blood flow in the vessel due to stenosis. Finally, in some cases, you’ll see signs of tissue loss, like an arterial ulcer with punched-out edges and a dry base, or even necrosis or gangrene. If you find these characteristics, suspect PAD.

Here’s a clinical pear! Not all ulcers on a physical exam will be arterial. They might present with a neuropathic, or a venous stasis ulcer as well. Okay, now that you suspect PAD, obtain an ankle-brachial index or ABI to assess the blood flow through arteries. The test involves measuring blood pressure at the ankle and the arm. Then, the ankle pressure is divided by the arm pressure to calculate the ABI. Here, you should measure both a pre and post-exercise ABI, because sometimes exercise can increase the blood flow to the legs accentuating a greater difference in blood pressure distal to the arterial lesion. In other words, obtaining the ABI post-exercise can increase the sensitivity of the results.

Alright, let’s look at our possible ABI results. Now, an abnormal ABI of less than 0.9 means that there’s an arterial insufficiency. Next, you should determine the severity of their condition by assessing for signs of severe disease, including rest pain, ulcer, necrosis, or even wet or dry gangrene.

Okay, before we move on to treatment, let’s talk about other possible ABI findings first. If the ABI results are normal, between 0.9 and 1.4, you should consider an alternative diagnosis. This can include musculoskeletal causes of limb pain and venous or neuropathic causes of ulcers.

Here’s a clinical pear! Sometimes ABI might be borderline ranging from 0.91 to 0.99. If this happens, definitely obtain the post-exercise ABI to get a real idea of what’s going on!

Now let’s go back and talk about the last ABI result. An ABI greater than 1.4 can indicate calcified arteries that cannot be compressed with an external blood pressure cuff. This is commonly encountered in diabetic patients due to the chronic glycation of their arterial wall leading to stiffening of the vessel. In these cases, your next step is to measure a toe brachial index or TBI. The arteries of the toe are often spared from being calcified. If TBI is normal, consider an alternative diagnosis. On the flip side, if TBI is abnormal, the patient has arterial insufficiency. As with abnormal ABI, you should determine the severity of their condition by assessing for signs of severe disease, including rest pain, ulcer, necrosis, or even wet or dry gangrene.