By Christopher M. Huff, M.D.
As my patients will tell you, my first item of business during a physical exam is to evaluate the feet. Particularly, I am interested in determining if the appropriate amount of blood has managed to navigate its way from the heart, along the arterial highway, to the farthest outreach of the body…the toes. Though the coronary arteries will forever remain in the spotlight of cardiovascular disease, atherosclerosis does not show favoritism and can affect any artery.
Peripheral arterial disease (PAD) is associated with a 5 year risk of death that is greater than Hodgkins disease or breast cancer. The reason for this is the strong link between PAD and myocardial infarction or stroke. Thus, patients with PAD require more aggressive risk factor modification and closer follow-up than patients without PAD. In addition, lower extremity revascularization can improve quality of life in patients with claudication and prevent amputation in patients with critical limb ischemia. Unfortunately, PAD often goes undetected due to the lack of appropriate screening from medical professionals.
We often find ourselves asking patients about chest pain, but how often are we asking about claudication? A few simple questions about exertional leg discomfort can help identify patients with PAD, but screening should not end there. Only 10% of patients with lower extremity PAD report classic symptoms of claudication, with 40% being asymptomatic. If the suspicion for PAD is high, as determined by risk factors and/or physical exam, non-invasive testing can assist in the diagnosis. Ankle-Brachial Index (ABI) is a simple non-invasive screening tool for PAD, and an ABI of <0.9 confirms the diagnosis.
There are two important caveats to be aware of when ordering and interpreting ABIs. First, similar to coronary artery disease, blood flow in the setting of PAD may be sufficient at rest, but insufficient with exertion. Therefore, if a patient can walk, rest and exercise ABIs should always be performed. Next, patients with diabetes and/or ESRD can have a normal ABI and still have an ischemic foot ulcer. This is due to poor collateral formation between the tibial vessels in these patients. Remember, the highest pressure between the dorsalis pedis artery (DPA) and the posterial tibial artery (PTA) is used to calculate the ABI. Thus, a diabetic patient with an occluded anterior tibial artery (ATA) but a patent PTA may have a normal ABI and an ischemic foot ulcer because of lack of collaterals. Given this, in diabetic and/or ESRD patients with a non-healing ulcer, it is important to look at the specific pressure for both the DPA and PTA. Toe pressure can be particularly helpful in this setting, as a toe pressure of less than 30 mmHg suggests that the ulcer is ischemic and will not heal without revascularization.
If there is any question regarding the presence or significance of PAD and the appropriate management strategy, do not hesitate to seek input from a PAD specialist. With appropriate screening, aggressive risk factor modification, and prompt referral to a specialist, the complications of PAD can be managed successfully.
Christopher M. Huff, M.D. practices cardiology with Cardiovascular Associates.