The prevalence of Peripheral Arterial Disease among patients with persistent leg pain

Any clinician dealing with patients in pain can testify that this unpleasant experience associated with tissue damage can often be very difficult to connect to an actual medical condition. That is particularly true in the absence of other symptoms connected with a suspected condition, prompting additional diagnostic investigation, usually with the use of modern diagnostic devices. However, many patients with undiagnosed PAD are referred to the wrong specialists or even receive incorrect treatment.

In this blog you will learn:

• How common is asymptomatic Peripheral Arterial Disease (PAD)?
• What is an Ankle-Brachial Index (ABI) assessment?
• What is PVR and its role in the diagnosis of Peripheral Arterial Disease (PAD)?
• How many patients are wrongly referred to orthopaedic surgeons?
• How can general practitioners and orthopaedic surgeons help screen for Peripheral Arterial Disease (PAD)?

How common is asymptomatic Peripheral Arterial Disease (PAD)?

Peripheral arterial disease (PAD) or lower extremity artery disease (LEAD) is, like many other cardiovascular diseases (CVDs), largely asymptomatic until already at an advanced stage. It is estimated that only 10% of patients with PAD are symptomatic, 40% are entirely asymptomatic, and the remaining 50% have atypical pain symptoms that could be attributed to other medical conditions (2, 3). Additionally, some studies have indicated that women are more likely to be asymptomatic than men (4, 5, 6, 7, 8). Women were also more likely to present with atypical symptoms (e.g. spinal stenosis) (9).

This brings us to the challenges involved with the diagnosis of PAD in patients with comorbid conditions that might mask the symptoms of PAD. The most obvious example is diabetes mellitus, a prominent factor in the greater incidence and morbidity of PAD (10, 11). Patients with diabetes are far more likely to have symptomatic PAD: men are 3.5 and females 8.6 times more likely to present with intermittent claudication than their non-diabetic counterparts (12).

Yet even they might evade timely diagnosis if they have extensive neuropathy that may mask such pain symptoms (13). Pain in the lower extremities is likewise the domain of orthopaedic surgeons, to whom patients are often referred whose symptoms are not actually associated with any musculoskeletal disease. In the absence of any other symptoms, but inclusion in risk groups (age, smoking status/history, diabetes, hypertension, etc.) preventive screening should be mandatory.

What is an Ankle-Brachial Index (ABI) assessment?

There are several established methods for the screening and diagnosis of PAD, but none as convenient and inexpensive as an ABI (Ankle-Brachial Index) assessment. The procedure consists of taking systolic blood pressure readings at the brachial artery of each arm and at the posterior tibial and dorsalis pedis arteries. The ABI is then calculated by taking higher values for each set of limbs and dividing the highest leg pressure with the highest arm one.

This can be done either with a sphygmomanometer and a Doppler probe or with an automated oscillometric-plethysmographic diagnostic device. While accurate and reliable, the first method is prone to user error, may take up to 30 minutes, and requires lengthy training (15). The same cannot be said for the latter as the device can take the measurements in one minute and is free of user errors (16, 17). It also shares its mode of operation with the pulse volume recording (PVR) diagnostic method.

What is PVR and its role in the diagnosis of Peripheral Arterial Disease (PAD)?

Measuring blood perfusion in limbs with the use of PVR is of vital importance not just for the diagnosis of PAD, but for assessing the success of revascularisation surgery before and after the procedure (18). In a manner similar to an ABI assessment, blood pressure cuffs are placed on either upper or lower extremities and partially inflated; they are connected to a pulse volume recorder, a device that displays changes in volume in the measured limb due to blood pressure changes as a waveform.

How many patients are wrongly referred to orthopaedic surgeons?

The two diagnostic methods were also used in a study on the prevalence of occult PAD in patients referred to orthopaedic surgeons. Conducted between July and December 2005 at the Philadelphia Veterans Affairs Medical Center (VAMC) in the state of Pennsylvania, it encompassed 50 patients with an average age of 63 years (19). Only patients over 50 years of age with leg pain but no history of trauma within the last three years or PAD were included, and they had to be referred by a general practitioner (19). They were screened for cardiovascular risk factors, diagnosis of the actual source of pain such as degenerative joint disease, and for PAD, utilising both ABI assessment and PVR analysis (19).

The results were telling of 50 patients, 10 (20%) had occult PAD, but only one of those presented with intermittent claudication (19). None of the 40 patients without PAD had intermittent claudication (19). Another important takeaway was the discovery that the prevalence of risk factors between the group with PAD, the group without PAD, and a control group was not statistically significant (19). So, what should GPs do before they refer a patient to an orthopaedic surgeon, and what should the latter do when the patient is already at their office?

How can general practitioners and orthopaedic surgeons help screen for Peripheral Arterial Disease (PAD)?

The problem of occult PAD goes beyond undiagnosed patients at orthopaedic surgeons’ clinics, though there are ways of mitigating that. The proliferation of oscillometric-plethysmographic diagnostic devices amongst GPs is one approach, coupled with a practical educational intervention (20, 21). Cautious action would also include equipping orthopaedic offices with the same equipment to help surgeons determine whether PAD is the cause of the patient’s pain and generally screen for the disease if GPs or other clinicians overlooked it.

High rates of occult PAD should prompt general practitioners to screen patients who present with any leg pain, even in the absence of risk factors and intermittent claudication, before referring them to an orthopaedic surgeon.

Managing Referrals in Vascular Medicine.