Peripheral arterial disease prevention and prevalence: study

Peripheral arterial disease, whether symptomatic or not, refers to occlusive disease of lower-limb arteries. It is most commonly caused by atherothrombosis, but may reflect other disease, such as arteritis, aneurysm, and embolism. In recent years, it has become evident that PAD is an important predictor of substantial coronary and cerebral vascular risk.

Increased awareness of the prognostic importance of PAD has led to a search for sensitive diagnostic markers. The ankle–brachial pressure index (ABPI) has emerged as a valid and reliable marker of PAD and its attendant vascular risk, particularly in patients without clinical features of PAD.

However, because awareness and implementation of the ABPI in general clinical practice is poor, the concept and prevalence of asymptomatic PAD is not widely appreciated, and PAD continues to be underdiagnosed and undertreated. There is also evidence that the management of risk factors in patients with symptomatic PAD is inadequate.

In this article, we aim to examine:

 
• ABPI as a valid and reliable diagnostic marker of PAD;  
• PAD, defined either by symptoms or an abnormal ABPI, as a significant independent risk factor for systemic atherothrombosis;  
• incorporating an assessment of PAD into the assessment of overall vascular risk; and  
• modifiable causal risk factors for PAD, and the potential for appropriate vascular risk factor control to reduce the burden of vascular disease.

We will not discuss the management of the lower-limb consequences of PAD.

The prevalence of peripheral arterial disease (PAD) in people aged over 55 years is 10%–25% and increases with age; 70%–80% of affected individuals are asymptomatic; only a minority ever require revascularisation or amputation.

Patients with PAD alone have the same relative risk of death from cardiovascular causes as those with coronary or cerebrovascular disease, and are four times more likely to die within 10 years than patients without the disease.

The ankle–brachial pressure index (ABPI) is a simple, non-invasive bedside tool for diagnosing PAD — an ABPI less than 0.9 is considered diagnostic of PAD.

About half of patients with PAD (defined by an abnormal ABPI) have symptomatic coronary or cerebral vascular disease.

The ABPI is an independent predictor of coronary and cerebrovascular morbidity and mortality.

Patients with PAD require medical management to prevent future coronary and cerebral vascular events.

There are currently insufficient data to recommend routine population screening for asymptomatic PAD using the ABPI.

Diagnosing peripheral arterial disease

Most clinicians think of PAD in terms of symptoms (intermittent claudication, rest pain) and abnormal signs (diminished peripheral pulses, ischaemic ulceration and gangrene). The clinical diagnosis and assessment of severity of intermittent claudication is not always reliable, and various structured questionnaires (notably World Health Organization/Rose and Edinburgh Claudication questionnaires) have been used in epidemiological studies. However, PAD can be confirmed in most cases by measuring the ABPI. This index is a simple, non-invasive bedside tool for diagnosing PAD that can be used by any clinician. An ABPI of less than 0.9 is diagnostic of PAD. In addition to providing a semi-quantitative and objective measure of the severity of symptomatic PAD, the index also allows for identification of asymptomatic PAD. The validity of the ABPI as a diagnostic marker of subclinical arterial vascular disease is confirmed by its adverse prognostic significance for coronary and cerebrovascular events.

Duplex scanning, magnetic resonance imaging, computed tomography and digital subtraction angiography are also useful in assessing PAD, but are generally used for anatomical localisation of arterial disease before intervention rather than for initial diagnosis.

Epidemiology of peripheral arterial disease

The incidence of symptomatic PAD increases with age, from about 0.3% per year for men aged 40–55 years to about 1% per year for men aged over 75 years. The prevalence of PAD varies considerably depending on how PAD is defined, and the age (and, to a lesser extent, sex) of the population being studied. Using the definition of an ABPI less than 0.9, most epidemiological studies report the prevalence of PAD to be about 10%–25% in men and women over 55 years of age. Although only about 10%–20% of people with PAD identified in epidemiological studies are symptomatic (usually with intermittent claudication), this may be an underestimate because of underascertainment of symptomatic cases. The prevalence of PAD rises with age (eg, from 10.6% in men aged 65–69 years to 23.3% in men aged 75–79 years in a population-based Western Australian study). On average, the prevalence of symptomatic disease at around 60 years of age is about 5%.

References

  _{1. Ogren M, Hedblad B, Isacsson S, et al. Ten year cerebrovascular morbidity and mortality in 68 year old men with asymptomatic carotid stenosis. BMJ 1995; 310: 1294-1298.}