Colleague Commenary: Sensible Screening for PAD In Asymptomatic Patients

Results from the German Epidemiological Trial on Ankle-Brachial Index (getABI), recently presented at the annual congress of the European Society of Cardiology, provide good evidence that there is a real need for primary care physicians to screen asymptomatic patients for peripheral artery disease (PAD).

In the study, 6,880 unselected patients 65 years and older were screened for PAD by their primary care physician using measurement of the ankle-brachial index (ABI). The researchers found that all-cause mortality at 1, 3, and 5 years was not significantly different between patients with symptomatic or asymptomatic PAD.

These results echo those of the San Diego Artery Study, which looked at asymptomatic patients with large vessel PAD. Beyond 10 years, the mortality for asymptomatic patients and symptomatic patients was virtually identical (N. Engl. J. Med. 1992;326:381-6).

Both studies suggest that asymptomatic patients with PAD are a very important patient population to identify. These trials show increased long-term (5-10 years) mortality rates for asymptomatic patients. The American Heart Association estimates that up to 8-12 million Americans have PAD and nearly three-quarters are asymptomatic. The key question is which asymptomatic patients should we be screening?

There are certain risk factors in asymptomatic older patients that should prompt a screening ABI:

• A 10-year Framingham Risk Score of greater than 20%.
• Established atherosclerotic vascular disease in another vascular bed, including the carotid, coronaries, mesenteric vasculature, cerebral vasculature, or the renal arteries.
• A family history of PAD.
• Hypertension/hyperlipidemia, especially if chronically poorly controlled.
• Chronic smoking.
• A history of diabetes (8-10 years) or chronic, poorly-controlled diabetes.
• Chronic kidney disease.

An ABI is very easy to do, is noninvasive, takes only a few minutes, and can be performed by a trained technician, physician assistant, or nurse.

If you identify a patient with PAD, who does not have an established coronary heart disease risk equivalent, you have immediately marked this patient for very intensive management of his or her comprehensive risk factor background--smoking cessation, blood sugar control, aggressive lipid management, lowering blood pressure, and aggressive lifestyle modification. This kind of management would go a long way toward reducing the risk of PAD progression and may even help to induce atheromatous plaque regression.

Screening has value beyond the identification and treatment of PAD. Patients with PAD are also likely to have other atherosclerotic disease, possibly in multiple vascular beds. We know that aggressive, comprehensive risk factor management in patients with atherosclerotic disease is associated with reduced cardiovascular morbidity and mortality, along with reduced risk for critical lower-limb ischemia and need for amputation.

ABI also makes sense for some patients without the classic PAD sign of claudication in the calf. Not all patients with PAD present with this symptom. Instead, a patient may present with buttock pain, proximal thigh pain, foot pain, knee pain, or arthralgia. Others may actually present with exertional weakness. Many of these symptoms are attributed to other etiologies, such as sciatica or osteoarthritis, rather than PAD. These are patients who should be considered for an ABI especially if supported by findings from a rigorous physical examination and a high index of suspicion.

If a patient has a positive ABI that suggests PAD, it is important to follow up with a Doppler arterial ultrasound. This can help reveal morphologic characteristics, as well as hemodynamic consequences, of lesions in the peripheral arterial tree. Visualizing abnormal velocity wave forms helps confirm the diagnosis.

If the ABI is suggestive of PAD and this is confirmed with Doppler arterial ultrasound, depending upon the severity encountered, magnetic resonance angiography should be considered to define more precisely the location and severity of atherosclerotic disease.

For these patients, aim to reduce hemoglobin A1c to at least 7% (and reduction to 6% likely confers even greater benefit), blood pressure to 130/80 mm Hg or less, and LDL cholesterol to less than 100 mg/dL. In addition, statin therapy is associated with reduced frequency and intensity of peripheral claudication. Finally, if a patient has PAD, they should be considered at high risk for cardiovascular disease and started on aspirin therapy. These patients should be encouraged to engage in lifestyle modification. Daily ambulation is associated with lower risk of disease progression and can also reduce the intensity of insulin resistance in patients with metabolic syndrome or diabetes mellitus.

The other question is one of reimbursement. It is difficult to get any screening test covered in asymptomatic patients. Lack of reimbursement poses a significant barrier to performing ABIs in asymptomatic patients and organized medicine should address this issue, especially in light of the results from more recent cohort studies and clinical outcome trials.

Not only should we be doing ABIs to screen for PAD in high-risk patients, we need to push the expansion of PAD screening coverage. The odds of discovering asymptomatic PAD with a screening test increases substantially as a function of age and increasing number of cardiovascular disease risk factors.