Peripheral arterial disease (PAD), cardiologist's perspective

Peripheral arterial disease (PAD) is not always atherosclerotic in origin, but in today’s cardiology practice it is usually a sign of generalised, multilevel atherosclerosis.

I - PAD tends to coexist with atherosclerotic lesions in other vascular beds, especially in the elderly.

In a study of 1802 men and women, mean age 80 years, 68% of subjects with PAD had coexistent CAD and 42% had prior ischemic stroke (1).

• Patients with PAD have an increased risk of angina, myocardial infarction, stroke, congestive heart failure and death compared to patients without PAD. In this group, the risk of non-fatal myocardial infarction is increased by 20-40%, and of heart failure – by 60%. Mortality in patients with PAD is two to seven times as high as in those without PAD. A 5-year follow-up in Edinburgh Artery Study showed a comparable increase in risk of coronary events and death in both patients with symptomatic and asymptomatic PAD (2).
• Both incidence and prevalence of PDA increase with age. Criqui et al. (3) estimated that PAD is present in 5.6% of subjects aged 38 to 59 years, in 15.9% of those aged 60 to 69 years, and in 33.8% of those aged 70 to 82 years.
  In individuals aged ≥65 years without cardiovascular disease, included in the Cardiovascular Health Study (4), the prevalence of PAD was 13.9% in men and 11.4% in women. However, in the oldest group, symptomatic PAD was present in 20% of male (mean age 80), and in 13% of female subjects (mean age 81).

II - The most frequent PAD symptom is intermittent claudication.

The most frequent PAD symptom is intermittent claudication, that is defined as muscle pain or weakness induced by exercise and relieved with rest, which occurs distal to the arterial obstruction.

• Atherosclerotic lesions most commonly involve the superficial femoral and popliteal arteries, and therefore, the pain of intermittent claudication is usually localized in the calf.
• When atherosclerotic obstruction affects the distal aorta and its bifurcation into the two iliac arteries, the pain is localized both in the buttocks or thighs, and in the legs (5).

III - However, typical symptoms of intermittent claudication in patients with diagnosed PAD are rather uncommon.

• Intermittent claudication is not the only symptom of lower extremities atherosclerosis, and limb pain elicited by walking may be relieved when exercise is continued or pain may be chronic, with mild exacerbation upon exercise (6)

Results of the PARTNERS study indicate that less than 11% of patients with PAD have “typical” intermittent claudication, while more than half have atypical symptoms of lower limb discomfort present at rest (7).

• With the progression of the disease; patients might have pain at rest, which is most prominent with leg elevation, and can be relieved by dependency.
• In subjects with most advanced stages of PDA, tissue hypoperfusion may lead to ischaemic ulcerations and necrosis. In consequence, in more than 30% of these patients major amputation is required (8).

Contrary to a common belief, typical symptoms of intermittent claudication in patients with diagnosed PAD are rather uncommon. According to different authors they occur in 20-30% of patients (3).

Asymptomatic atherosclerotic narrowings are present in almost 20% of persons above 55 years of age, which makes it the most prevalent form of atherosclerosis (9).

• Although symptoms typically occur as the luminal obstruction is in excess of 50%, even patients with severe disease may remain asymptomatic if extensive collateralisition in the lower extremity has developed (10).

IV - History and physical examination are much less accurate than objective measurements, such as the ankle/brachial index.

Persons with advanced PAD of the lower extremities have diminished or absent arterial pulses, the diagnosis seems easy. However, history and physical examination are much less accurate than objective measurements, such as the ankle/brachial index. Pulses palpation is neither sensitive nor specific for peripheral arteries disease.

In a study of males and females of mean age 66 years, among whom 11% had PAD; sensitivity of abnormal pulses examination was 77%, whereas specificity of normal pulses in the absence of disease was 86% (11).

Noninvasive tests used to asses lower extremity arterial blood flow include :

1. measurement of ankle and brachial artery systolic blood pressures
2. characterisation of velocity wave form
3. duplex ultrasonography

Measurements of ankle and brachial artery systolic blood pressure using a Doppler probe and blood pressure cuffs allow calculation of the ankle/brachial index (ABI), which is normally 0.9 to 1.2. An ABI of less than 0.90 is 95% sensitive and 99% specific for the diagnosis of PAD (3).

Using the ankle-brachial index (ABI) of less than 0.95 as indicative of PAD, the prevalence of 6.9% was observed in patients aged 45-74 years, and only 22% of them had symptoms. (8).

The discrepancy between typical symptoms and the presence of PAD defined by ABI was shown in the Rotterdam study, a population-based analysis of 7715 patients (2). Although a prevalence of intermittent claudication ranged from about 1% in the group aged 55-60 years to 4.6% in the group aged 80-85 years, the PAD diagnosed on the basis of ABI was found in 16.9% of men and 20.5% of women aged 55 and older.

ABI measurement should be widely used to detect PAD. According to Hirsch (12), this test should be done at least in the following patient categories:

1. patients with discomfort in lower limbs after exercise
2. patients with non-healing wounds
3. patients above 70 years of age
4. smokers and/or diabetics above 50 years of age.

Conclusions

PAD remains unrecognised too often or is discovered in advanced stage. ABI measurement is a simple examination that takes 10-15 minutes and that can be performed in every outpatients clinic.

Early diagnosis of PAD allows for immediate implementation of measures to reduce atherosclerotic risk.

The presence of PAD should be considered as an index of systemic atherosclerosis, as patients with PAD have a higher incidence of coronary heart disease and atherosclerotic abnormalities of cerebral circulation. Thus, patients with PAD should undergo thorough medical evaluation to exclude or confirm the coexistence of coronary heart disease, carotid artery stenosis or other lesions.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.