Peripheral Vascular Disease Imaging 

Peripheral vascular disease (PVD), or atherosclerosis of peripheral vessels, is the most common cause of symptomatic stenosis in the human vascular tree. The pathogenetic mechanisms that lead to PVD are similar to those of coronary artery disease (CAD). The risk factors are also similar and include a positive family history, cigarette smoking, diabetes, hypertension, dyslipidemia, advanced age, and physical inactivity, among others. Angiograms demonstrating PVD appear below.^{[1, 2]}

Percutaneous revascularization with techniques such as percutaneous transluminal angioplasty (PTA), a less invasive option in the management of peripheral vascular disease (PVD), has been furthered by the work of pioneers such as Dotter and Gruntzig.^[3] Over the past 30 years, there has been steady growth in the use of PTA, and it has become the first-line therapy for PVD (see the images below).^{[4, 5, 6]}

This article will discuss diagnostic imaging techniques used in PVD.

Patient education

For patient information resources, see the Circulatory Problems Center and Cholesterol Center, as well as Peripheral Vascular Disease, High Cholesterol, and Cholesterol FAQs.

Noninvasive and invasive modalities are used for diagnostic evaluation in iliofemoral disease. Noninvasive testing includes Doppler ultrasonography and magnetic resonance angiography (MRA).^[7]

Doppler ultrasonography and evaluation of the ankle-brachial index

For Doppler ultrasonography, pneumatic cuffs are placed along the leg and are inflated to suprasystolic pressures. During controlled cuff deflation, a Doppler probe is placed over the dorsalis pedis artery or posterior tibial artery to detect the onset of flow. Normally, the systolic blood pressure in the leg is slightly higher than that in the arm; therefore, the normal ankle-brachial index (ABI) of systolic blood pressure should be 1.0 or slightly greater. An ABI of less than 0.95 is considered abnormal. Patients with leg claudication typically have an ABI of less than 0.8. In patients with ischemia at rest, the ABI is frequently less than 0.4.

Magnetic resonance angiography

MRA is another noninvasive approach for imaging the peripheral circulation. It does not involve the risk of intravascular catheterization or conventional contrast agents.^[8]

Angiography

Invasive imaging with contrast arteriography is required when the diagnosis remains unclear or endovascular procedures are planned (see the images below).

Although digital subtraction angiography is the gold standard, duplex ultrasound has shown good accuracy in the detection of femoropopliteal lesions. Khan et al proposed 200 cm/s peak systolic velocity and a 2.0 velocity ratio to discern between < 70% and ≥ 70% stenosis in the femoropopliteal arterial segment.^[9]

Atherosclerotic disease that causes stenosis of more than 50% in at least 1 renal artery is encountered in 30% of patients with CAD, 38% of patients with abdominal aortic aneurysms (AAAs), and 39% of patients with iliofemoral disease (see the image below). In approximately one third of cases, renal artery disease is bilateral. About 11% of renal arteries with stenoses of greater than 60% progress to total occlusion within 2 years.^{[10, 11]}

In the past, captopril renography was used in the diagnosis of bilateral renal artery stenosis. The possibility of the development of renal atherosclerosis may be assessed just as accurately on the basis of clinical parameters, such as advanced age; female sex; the presence of atherosclerosis in other vascular beds; the recent onset of hypertension; smoking; the presence of abdominal bruits; an elevation in the creatinine level; and hypercholesterolemia. MRA has emerged as a potentially useful noninvasive imaging method for diagnosing renal artery stenosis.

Flush abdominal aortography in patients undergoing coronary arteriography may be performed when the likelihood of renovascular disease is high. This imaging is usually performed by placing a pigtail catheter at the level of the first lumbar vertebra and injecting contrast material at a rate of 20 mL/s to achieve a total contrast-agent volume of 6-12 mL.

Subclavian and brachiocephalic artery disease

Patients with atherosclerotic disease of an upper extremity may develop symptoms of ischemia, but these occur less commonly than do symptoms of iliofemoral disease. Most patients with atherosclerotic obstruction of the subclavian or brachiocephalic arteries are asymptomatic. Usually, the condition is incidentally discovered when there is a difference between blood pressure measurements of a patient's arms or when evidence of obstructive disease is observed during angiography or during a noninvasive evaluation. An angiogram of subclavian artery stenosis appears below.

Carotid artery disease

The types of stroke include ischemic stroke, cardioembolic stroke, and others.

A diagnosis of carotid artery disease by means of physical examination alone is probably inaccurate. The anatomic diagnosis of carotid disease may be confirmed through noninvasive or invasive angiographic approaches (see the image below). Some authors advocate the use of duplex and transcranial Doppler ultrasonography as the first step in the evaluation of carotid disease; this approach is accurate in 90% of cases.

MRA is emerging as a noninvasive means of visualizing the carotid, vertebrobasilar, and major intracranial vessels, but it provides less detail than do contrast-enhanced modalities. When the combination of MRA and Doppler ultrasonography is used, however, nearly 100% specificity in defining the hemodynamic severity of carotid stenoses is achieved.

Although aneurysms may affect any arterial bed, infrarenal abdominal aortic aneurysms (AAAs) account for most arterial aneurysms. An AAA is defined as an aneurysm having a diameter of greater than 3 cm. Most AAAs are incidentally discovered during abdominal ultrasonography or angiographic examinations performed for other indications.

The growth rate for AAAs is variable; the average growth rate is 0.3-0.5 cm per year. Whether or not an aneurysm ruptures is most strongly related to its size.

Accurate sizing requires the performance of abdominal ultrasonography, computed tomography (CT) scanning, or magnetic resonance imaging (MRI). Aortography is not a reliable means of determining the size of the aneurysm, because a laminated thrombus, if present, may cause the size of the aneurysm to be underestimated.