Case Study

A 57-year-old man visits your office for refills of simvastatin (Zocor) and paroxetine (Paxil). He says his friend had “a bypass operation on the arteries in his legs,” and asks if you think he should be “checked for that disease.” He has never had symptoms of claudication.

Case Study Questions

1. Based on the current recommendation from the U.S. Preventive Services Task Force (USPSTF) on screening for peripheral arterial disease (PAD), what is the most appropriate next step for this patient?

   A. Offer screening for PAD with an ankle-brachial index.

   B. Offer screening for PAD with palpation of his distal pulses.

   C. Counsel him that screening him for PAD would have few or no benefits.

   D. Offer screening for PAD using a validated clinical PAD questionnaire.

2. Which of the following statements about screening for PAD is/are correct?

   A. A Doppler-recorded ankle-brachial index is more accurate than other noninvasive screening methods.

   B. The accuracy of an ankle-brachial index decreases as lower extremity arterial stenosis worsens.

   C. Most patients with PAD are asymptomatic.

   D. A classic history of claudication accurately predicts PAD.

Answers

1. The correct answer is C. The USPSTF recommends against routine screening for PAD. The USPSTF found fair evidence that screening with the ankle-brachial index can detect PAD in asymptomatic adults. There is also fair evidence that screening for PAD among asymptomatic adults in the general population would have few or no benefits. The prevalence of PAD in this group is low, and there is little evidence that treatment of asymptomatic PAD, beyond treatment based on standard cardiovascular risk assessment, improves health outcomes. Furthermore, the USPSTF found fair evidence that screening asymptomatic adults with the ankle-brachial index could lead to a small degree of harm, including false-positive results and unnecessary work-ups. Thus, the USPSTF concludes that, for asymptomatic adults, the harms of routine screening for PAD exceed the benefits.

PAD refers to atherosclerotic occlusive disease of the lower extremities’ arterial system distal to the aortic bifurcation. Risk factors associated with PAD include older age, cigarette smoking, diabetes mellitus, hypercholesterolemia, hypertension, and possibly genetic factors. There are no significant sex differences in the overall prevalence of PAD in the general population. Over a five-year period, 25 to 35 percent of persons with PAD will have a myocardial infarction or stroke, and an additional 25 percent will die, usually from cardiovascular causes.

Smoking cessation and lipid-lowering agents improve claudication symptoms and lower-extremity function in patients with symptomatic PAD. Smoking cessation and physical activity also increase maximal walking distance in men with early PAD. Counseling for smoking cessation, however, should be offered to all patients who smoke regardless of the presence of PAD. Similarly, physically inactive patients should be counseled to increase their physical activity regardless of the presence of PAD.

2. The correct answers are A and C. The ankle-brachial index, a ratio of Doppler-recorded systolic pressures in the lower and upper extremities, is a simple and accurate noninvasive test for screening for and diagnosis of PAD. This refers specifically to the Doppler-recorded ratio of systolic pressures in the lower and upper extremities. This method has demonstrated better accuracy than other methods of noninvasive screening, including history-taking, questionnaires, and palpation of peripheral pulses. An ankle-brachial index value of less than 0.90 (95 percent sensitive and specific for angiographic PAD) is strongly associated with limitations in lower-extremity functioning and physical activity tolerance. The accuracy of this screening tool increases as lower extremity stenotic lesions worsen.

Palpating distal pulses to screen for PAD is not as accurate as using the ankle-brachial index. An abnormal posterior pulse has a sensitivity of 71 percent, a positive predictive value of 48 percent, and a specificity of 91 percent. An abnormal dorsalis pedis pulse is only 50 percent sensitive, and this artery is absent in 10 to 15 percent of the population. Likewise, the sensitivity and predictive value of a positive history of claudication are only 54 percent and 9 percent, respectively, when using the ankle-brachial index as the screening method of choice.

The American Heart Association estimates that as many as 8 to 12 million Americans have PAD and that nearly 75 percent of them are asymptomatic. The disease spectrum for symptomatic patients ranges from mild, intermittent claudication resulting in calf pain to severe, chronic leg ischemia requiring arterial bypass or amputation.