Peripheral Arterial Disease: Medical Care and Prevention of Complications

David L. Dawson, MD; William R. Hiatt, MD; Mark A. Creager, MD; Alan T. Hirsch, MD

Disclosures

Prev Cardiol. 2002;5(3) 

In This Article

Diagnosis of PAD and Intermittent Claudication

The diagnosis of PAD is frequently overlooked. Many patients present with concurrent problems, and treatment of intermittent claudication is often not given priority in patients with multiple, coexisting, chronic medical conditions. For sedentary patients, intermittent claudication may not be troublesome and generally goes unreported. Even patients with obvious symptoms may under-report claudication symptoms, accepting "aches and pains" as an inevitable consequence of aging. Additional factors that may contribute to the under-diagnosis of PAD include the limited training that most physicians receive in the management of this disease, some practitioners' lack of ready access to an inexpensive hand-held Doppler device for determination of the ankle-brachial index (ABI), or lack of access to noninvasive vascular laboratory services.[18] Furthermore, PAD is not a prominent diagnosis in established clinical coding systems, and thus its prevalence as an outpatient or discharge diagnosis is likely to be under-reported in many health care systems.

The first step toward making the diagnosis of PAD is the identification of patients at risk for the disease. All patients with symptoms of claudication should undergo a thorough medical evaluation, including a global assessment of atherosclerosis risk factors; if warranted, behavioral and pharmacotherapeutic interventions should be initiated to rapidly achieve optimization of these risk factors. Primary risk factors include advancing age, diabetes, cigarette smoking, hypertension, hyperlipidemia, hyperhomocysteinemia, and postmenopausal status.[19] Of note, a person over the age of 45 years who smokes more than 15 cigarettes a day is nine times more likely to develop intermittent claudication than is a nonsmoker in a similar age group.[20]

The diagnosis of PAD in patients with intermittent claudication or critical limb ischemia can typically be made on the basis of a thorough patient history and physical examination. Additional evaluation of PAD is multimodal, and the techniques used vary, depending on the nature and severity of the patient's presenting problem. Most PAD patients can be appropriately managed without specialized diagnostic services or interventions.

Claudication is characteristically described as pain, aching, or muscle fatigue occurring after the onset of exercise (walking) and relieved by rest. The history of PAD is characteristic and consistently reproducible, and may alone be diagnostic for many individuals. A complete physical examination is indicated, however, to evaluate potentially important contributing factors that may have an impact on clinical management. Palpation of pulses at appropriate sites should be correlated with symptom severity; location and auscultation of bruits may also be helpful.

All patients with claudication should be evaluated for atherosclerotic risk factors, including hypertension, lipid abnormalities, and diabetes mellitus. The following blood tests should be performed in new patients presenting with PAD, to screen for common hematologic pathologies, diabetes mellitus, renal insufficiency, and dyslipidemias[1]:

  • Complete blood count

  • Platelet count

  • Fasting blood glucose or hemoglobin A1c

  • Creatinine

  • Fasting lipid profile

  • Urinalysis (for glycosuria/proteinuria)

In addition, the following laboratory investigations are indicated for PAD patients with early-age onset of disease, for those with a personal or family history of thrombotic events, or when there is a lack of common risk factors for atherosclerosis:

  • Hypercoagulability screening

  • Homocysteine levels (either fasting or after methionine loading)

The ABI is a test that is easily performed in any patient care setting and is important in the diagnosis of PAD. Arterial systolic pressure measurements are made with a continuous-wave Doppler ultrasound instrument (5-7 MHz) and conventional blood pressure cuffs. The ABI is determined by dividing the systolic pressure at the ankle (the higher of the tibial artery pressures) by the systolic pressure at the arm (the higher of the brachial artery pressures).

An ABI <0.90 establishes a diagnosis of PAD, with a 95% sensitivity and specificity of nearly 100%.[21] Although ABI values between 0.50 and 0.90 are common in patients with intermittent claudication, the relationship between ABI values and the severity of claudication is difficult to predict. Some individuals may experience moderate to severe symptoms despite a normal or near-normal ABI (as with aortoiliac stenoses), whereas others may experience few symptoms or complain of fewer symptoms, even with a low ABI. The ABI is a useful and objective indicator of disease severity and may also be helpful in identifying patients at increased risk for development of nonhealing wounds or progression to amputation. A lower ABI value predicts a higher incidence of atherosclerotic disease elsewhere in the circulation (coronary or cerebral). Thus, the ABI is more than a diagnostic tool for PAD. It can provide an objective indication of the systemic burden of atherosclerosis.

The Walking Impairment Questionnaire (WIQ) is a PAD-specific instrument used to assess the severity of PAD patients' walking disability. The WIQ is a tool that measures functional status by grading community-based walking ability with questions about walking distance, walking speed, stair climbing, and symptoms of intermittent claudication (pain symptoms). The WIQ can be a useful tool for assessing PAD, particularly in patients without classic claudication symptoms but who nonetheless have walking impairments that may be indicative of PAD. Also, the WIQ is useful to assess changes in walking capacity with treatment. In addition, broader functional status questionnaires, such as the Medical Outcomes Study Short Form-36 (SF-36), may be used for patient evaluation in the office, but these are more commonly used in the setting of clinical trials or outcome studies.

Treadmill testing is the best means to objectively measure a patient's walking performance: the patient walks on a treadmill preset for speed and incline and reports the first onset of pain (giving a measure of pain-free walking distance, PFWD) and the point at which pain becomes severe enough to stop walking (maximal walking distance, MWD). Results from the WIQ have been validated against objective data from treadmill testing.

A treadmill test may be considered to monitor the results of claudication therapies, including exercise training, claudication drugs, angioplasty, and surgery. Treadmill testing may also be useful to distinguish nonvascular causes of leg pain from true intermittent claudication.

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