Cliff Shearman

Introduction

Peripheral arterial disease (PAD) is an extremely common condition.

This is encouraging as it suggests that there may be a window of opportunity in which to identify and try to slow or reverse the progression of PAD. In this study the prevalence of both symptomatic and asymptomatic PAD increased with age and was more common in lower socio-economic groups. Both of these are important issues to consider when comparing the treatment of PAD with other cardiovascular diseases.

Patients with symptomatic PAD have reduced mobility and quality of life, which equates to some cancers, but PAD is also a powerful marker of cardiovascular risk, equating to a previous myocardial infaction.³ In a survey of 1886 patients with PAD, 58% had coronary artery disease and 34% had suffered a cerebrovascular event.⁴

Five years after diagnosis of PAD the mortality risk of the patient is twice that of a patient with breast cancer.

In summary, PAD is present in over 29% of the adult population and in the majority is asymptomatic. Apart from the impact on the patient in those with symptoms, PAD also identifies patients at extremely high risk of cardiovascular events, particularly if they have arterial disease elsewhere (Fig. 3.1). The key aims of treatment of PAD should be reduction of cardiovascular risk and improvement of the symptoms. Despite these stark figures, evidence suggests that many patients with PAD remain undiagnosed and even those who have been identified get suboptimal treatment, especially when compared to patients with coronary artery disease.⁷ This chapter will address the diagnosis and detection of PAD, factors affecting cardiovascular risk and medical treatments that may improve the symptoms of PAD.

PAD diagnosis and screening

Identification of PAD may be relevant to three patient groups. Firstly, in patients who present with primary symptoms affecting the legs who are at increased cardiovascular risk and may also be suitable for treatment of their claudication. Secondly, patients already at increased cardiovascular risk (e.g. after MI or stroke) when the diagnosis of PAD identifies a subgroup (polyvascular disease) who are at extremely high risk of cardiovascular events. The final group is asymptomatic patients in whom the identification of PAD may allow attempts to reduce cardiovascular risk and prevent disease progression. The evidence of identifying arterial disease in each of these groups is examined.

In symptomatic patients the diagnosis of PAD can be made on structured questioning, examination and measurement of ankle–brachial pressure index (ABPI). Typical muscular pain in the calf or thigh and buttocks on walking, combined with absent lower limb pulses, is strongly suggestive of PAD (Fig. 3.2). However, many patients have comorbidities, such as arthritis, which can confuse the history and pulse palpation may be difficult. Based on the above clinical criteria alone PAD will be missed in many individuals, and objective methods of assessment are needed, especially in asymptomatic people.⁸ Measurement of ABPI has been shown to be a reproducible method of confirming the diagnosis and is widely applicable in primary and secondary care⁹ (Fig. 3.3).

In a few patients in whom there remains uncertainty about the diagnosis, duplex ultrasound scanning should be undertaken to identify PAD. Treadmill exercise testing may be helpful to determine the dominant pathology in patients with other comorbidities that limit walking, such as arthritis.

This lack of awareness of the significance of PAD has been partly addressed at a national level. In the UK reduction of cardiovascular deaths is a stated aim of the Government and there are financial incentives through the General Medical Services (GMS) contract in primary care to identify and treat risk factors in patients with CHD and stroke. In April 2012 diagnosis of PAD will be included in the GMS contract and the National Institute of Health and Clinical Excellence (NICE) will publish guidelines on the mangement of PAD in mid 2012.

The diagnosis of PAD in these groups would place them in an extremely high-risk group for further cardiovascular events and appropriate attention could be given to modifying their risk factors.

The observation that a reduced ABPI, even in asymptomatic patients, correlates with increased cardiovascular risk prompts the concept of screening the adult population.¹⁵

PAD is common in the adult population and identification using ABPI is a simple, inexpensive test. Perhaps one of the most attractive aspects of using ABPI is that it identifies a high-risk individual before they develop clinical problems such as angina, MI or stroke.

Although appealing, at present there is no evidence that screening the adult population in general for PAD using ABPI would be of benefit or cost-effective and further work is needed to clarify this. However, the evidence for the measurement of ABPI in all patients with leg pain on walking, or with evidence of coronary or cerebrovascular disease, and patients with risk factors known to increase cardiovascular risk (e.g. diabetes, hypertension and raised cholesterol) is very strong.

Modifying cardiovascular risk

There is overwhelming evidence for the benefits of identifying and correcting risk factors such as hypertension, dyslipidaemias, diabetes and obesity in patients with PAD. Active intervention to aid smoking cessation, increased exercise as well as the use of antiplatelet agents will result in a marked reduction in cardiovascular morbidity and mortality (see Chapter 1). Despite such evidence the delivery of this aspect of medical treatment remains poor. In the ongoing REACH registry of patients at increased cardiovascular risk principally being managed in primary care, only a minority of patients with PAD receive adequate medical treatment.¹⁷ Even in patients referred to secondary care only 70% were on antiplatelet therapy and 44% taking a statin.¹⁸ Perhaps most disappointing of all, even after secondary care involvement there still remains a number of patients receiving inadequate treatment. In a retrospective review of 109 patients who had undergone amputation due to PAD at the time of referral for prosthesis fitting only 41% had been prescribed a statin and only 60% were taking an antiplatelet agent; 39% of patients were on both a statin and antiplatelet agent, but 32% had been prescribed neither.¹⁹

Lay knowledge of PAD too is poor compared to CHD and stroke. In a group of 2501 adult Americans only 26% had ever heard of PAD. Of those with awareness of PAD 56% were aware it was associated with smoking and approximately 25% were aware it was linked to MI, stroke and amputation.²⁰ Secondary prevention clinics for CHD have been demonstrated to save lives and it seems reasonable to extrapolate this benefit to patients with PAD.²¹

Medical treatments for symptomatic PAD

It is important that all patients receive clear and appropriate advice about their condition and how they can improve their prognosis.

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