Practice Essentials
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. [1, 2] PVD, also known as arteriosclerosis obliterans, manifests as insufficient tissue perfusion resulting from atherosclerosis compounded by emboli or thrombi. The atherosclerotic process may gradually progress to complete occlusion of medium-sized and large arteries. it is estimated that 1% of persons older than 50 years in the United States have pulmonary arterial disease or chronic limb ischemia. [3]
Imaging modalities
The criterion standard for intraluminal obstruction is arteriography. Delay in performing arteriography in the setting of limb ischemia can result in delayed treatment. If time allows, arteriography can prove useful in discriminating thrombotic disease from embolic disease.
Doppler ultrasound studies are useful as primary noninvasive studies to determine flow status. Upper extremities are evaluated over the axillary, brachial, ulnar, and radial arteries. Lower extremities are evaluated over the femoral, popliteal, dorsalis pedis, and posterior tibial arteries.
Carotid duplex ultrasonography (US) is a noninvasive means by which to estimate the degree of cervical carotid stenosis. US has the advantage of being available as a portable examination in the intensive care unit (ICU) or the coronary ICU. Carotid CT angiography (CTA) is a commonly performed imaging study in stroke centers. [3]
Magnetic resonance imaging (MRI) may be beneficial because of its high visual detail. Plaques are easily seen, as well as the difference between vessel wall and flowing blood. MRI may be limited in the emergency setting because of its location and the technical skill required. Benefits of magnetic resonance angiography (MRA) include high diagnostic accuracy and the avoidance of exposure to ionizing radiation; drawbacks include limited availability and increased cost. Time-of-flight (TOF) MRA is useful for patients who cannot tolerate iodinated contrast agents used in CTA. Contrast-enhanced MRA using a gadolinium MR agent offers improved visualization in areas of high-grade stenosis where TOF MRA may falsely indicate a short-segment occlusion. [4, 5, 6, 7]
Quiescent interval slice-selective (QISS) MRA is a cardiac-gated technique described by Edelman et al for the evaluation of the lower extremities. [8]
Computed tomography (CT) can be of use in the emergency department because of its availability. Contrast studies are most useful for imaging arterial insufficiency. PVD often coexists with risk factors for contrast-induced renal failure. High-definition CT studies may help guide treatment decisions. Benefits of CT angiography (CTA) include rapid noninvasive acquisition, wide availability, high spatial resolution, and the ability to generate isotropic datasets on 64-detector-row and higher CT scanners; drawbacks include exposure to iodinated contrast and ionizing radiation.
Molecular imaging with radionuclide-based approaches may potentially provide a novel noninvasive assessment of biologic processes in PVD, such as angiogenesis and atherosclerosis.
(Angiograms demonstrating PVD are shown below.)
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. [9] There has been steady growth in the use of PTA, and it has become the first-line therapy for PVD (see the images below). [10, 11]
Percutaneous transluminal angioplasty of superficial femoral artery stenosis, performed with a long balloon via a contralateral femoral approach.
Angiogram obtained after percutaneous transluminal angiography for superficial femoral artery stenosis.
Iliofemoral Disease
Noninvasive and invasive modalities are used for diagnostic evaluation in iliofemoral disease. Noninvasive testing includes Doppler ultrasonography and magnetic resonance angiography (MRA). [12, 6]
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. [13]
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. [4, 5, 14]
Angiography
Invasive imaging with contrast arteriography is required when the diagnosis remains unclear or endovascular procedures are planned (see the images below).
Preangioplasty left superficial femoral artery angiogram in a middle-aged woman with severe left leg claudication and an ankle-brachial index of 0.5 on preadmission noninvasive assessment was recorded via a contralateral approach after sterile prepping and draping of the patient, administration of conscious sedation, the infiltration of local anesthetic (usually lidocaine 1% or 2% solution) at the right femoral access site, placement of an arterial sheath in the femoral artery, and advancement of the contra guide catheter over 0.035-in guidewire under fluoroscopic guidance. The tip of the guide catheter is taken beyond the aortobifemoral junction and positioned into the right iliac artery. An angiogram (as shown) is obtained after the guidewire is removed. The proximal end of the catheter is connected to a manifold and 4-8 mL of contrast agent is manually injected during cineangiographic recording. The image may be played in a loop, or a particular frame may be saved for use as a roadmap during angioplasty. Intravenous antithrombin agent, usually heparin, is administered as a bolus (generally 3000-4000 IU) before angioplasty. The patient's activated clotting time is monitored, with continuous monitoring of intra-arterial pressure, pulse oximetry, and heart rate.
Renal Artery Stenoses
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. [15, 16, 17]
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 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, Brachiocephalic, and Carotid Artery Disease
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
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. The types of stroke include ischemic stroke, cardioembolic stroke, and others.
MRA has emerged as a noninvasive means of visualizing the carotid, vertebrobasilar, and major intracranial vessels, but it provides less detail than 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.
Abdominal Aortic Aneurysm
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 that is 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/yr. 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). [18, 19, 20] 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.
Guidelines
The American College of Radiology in its Appropriateness Criteria on pulsating abdominal masses noted that imaging studies are important in diagnosing the cause of a pulsatile abdominal mass and, if an AAA is found, in determining its size and involvement of abdominal branches. The ACR recommendations for diagnostic imaging and interventional planning and follow-up include the following [21, 22, 23] :
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Ultrasound (US) is the initial imaging modality of choice when a pulsatile abdominal mass is present.
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Noncontrast computed tomography (CT) may be substituted in patients for whom US is not suitable.
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Contrast-enhanced multidetector CT angiography (CTA) is the best diagnostic and preintervention planning study, accurately delineating the location, size, and extent of aneurysm and the involvement of branch vessels.
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Magnetic resonance angiography (MRA) may be substituted if CT cannot be performed.
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After repair of AAA, CTA of the abdomen and pelvis and MRA of the abdomen and pelvis are appropriate follow-up procedures.
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FDG-PET remains primarily a research tool but shows promise for assessing the metabolic activity of aneurysms.
The U.S. Preventive Services Task Force recommends a one-time screening for AAA with ultrasonography in men who are 65-75 years of age and have a history of smoking (ie, “ever smoker”: at least 100 cigarettes during lifetime). They also recommend selectively offering screening for mean 65-75 years of age who do not have a smoking history. They recommend against routine screeing in women who have never smoked and feel there is insufficient evidence to recommend screening in women who are 65-75 years of age and have a smoking history. [24, 25]
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Bilateral aortoiliac stenosis.
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Superficial femoral artery stenosis causing claudication.
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Percutaneous transluminal angioplasty of superficial femoral artery stenosis, performed with a long balloon via a contralateral femoral approach.
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Angiogram obtained after percutaneous transluminal angiography for superficial femoral artery stenosis.
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Left subclavian artery stenosis.
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Left carotid artery stenosis.
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Left renal artery stenosis.
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Preangioplasty right iliac angiogram in a middle-aged man with severe right leg claudication and an ankle-brachial index of 0.4 on preadmission, noninvasive assessment. The patient underwent sterile prepping and draping, conscious sedation was provided, infiltrating local anesthetic (usually lidocaine 1% or 2% solution) was administered at the femoral access site, an arterial sheath was placed in the femoral artery, and the guide catheter was advanced over 0.035-in guidewire under fluoroscopic guidance. Once the tip of the guide catheter is taken beyond the aortobifemoral junction and positioned into the right iliac artery, an angiogram (as shown) is obtained. After the guidewire is removed, the proximal end of the catheter is connected to a manifold, and 4-8 mL of contrast agent is manually injected during cineangiographic recording. The image may be played in a loop, or a particular frame may be saved for review during angioplasty. An intravenous antithrombotic agent, usually heparin, is administered before angioplasty. The patient's activated clotting time is monitored, with continuous monitoring of intra-arterial pressure, pulse oximetry, and heart rate.
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After an initial diagnostic angiogram is obtained for use as a roadmap, a 0.018-in guidewire is introduced into the side opening of a Y-connector (attached to the manifold at 1 end and the proximal end of the guide catheter at the other). A small torque device is used over the proximal end of the guidewire for steering purposes, while a small terminal bend is created by hand over the distal end before the guidewire is introduced into the guide catheter. The wire is advanced through the 6F contra guide across the midright iliac stenosis. The passage of the guidewire is monitored with fluoroscopy and by injecting small amounts of contrast agent. Occasionally, a combination of torque and forward pressure is required to cross the lesion. In tight lesions, the balloon catheter is sometimes advanced as well and used as support for guidewire passage.A peripheral angioplasty balloon is prepared by connecting its proximal port to an inflating device that contains a half-and-half imaging contrast agent and sterile saline solution. Negative pressure is applied to extrude any air bubbles. The inflating device is left in negative pressure during advancement of the balloon with 1 hand over the guidewire, which is held with the other hand. The balloon is advanced beyond the distal end of the guide catheter and straddled across the stenosed segment. A small amount of contrast agent is injected to confirm proper positioning of the balloon.The balloon is inflated by dialing up the pressure with the inflation device to several atmospheres, usually 4-8 bars. The mixed contrast agent/saline solution contained in the inflation device moves gradually into the balloon due to the increasing pressure and, as the balloon expands, it becomes visible under fluoroscopy (as shown). The balloon is left in the inflated position for several seconds to exert circumferential pressure on the stenosed arterial segment and expand the luminal dimension. The balloon is deflated by drawing negative pressure through the inflation device. Once deflated, it is gradually pulled back into the guide catheter while the wire is retained across the lesion.
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Angiogram obtained after percutaneous transluminal angioplasty shows increased luminal diameter at the stenotic segment, but it still appears to be narrow by at least 60%. There is moderate dissection, and the flow into the distal iliac artery is somewhat slow, but no filling defect (which may represent clot) is present. To patch the dissection, a self-expanding stent-balloon catheter is prepared in a manner similar to that used for a balloon catheter; however, before its insertion into the guide catheter, no negative pressure is applied. The stent catheter is advanced over the guidewire through the guide catheter beyond its distal end and taken across the lesion. The stent is positioned over the dissection by ascertaining its position by injecting a small amount of contrast material through the guide. The stent is deployed by pulling the overlying sleeve while the self-expanding stent gradually opens, beginning at the distal end. Every effort is made not to let the catheter move. The sleeve may always be advanced as long as it does not come back beyond the proximal end of the stent if repositioning becomes necessary. The sleeve and stent-balloon catheter are withdrawn, and the guidewire remains in place across the lesion.
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Poststenting angiogram made following withdrawal of the guidewire. The guidewire is withdrawn after it is confirmed that no flap, dissection, or filling defect is present. The angiogram shows that the residual stenosis in the iliac artery is 0%. The guide catheter is finally withdrawn. The left femoral access site that provided a contralateral approach to the right iliac stenosis is closed with a percutaneous closure device.
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Preangioplasty left superficial femoral artery angiogram in a middle-aged woman with severe left leg claudication and an ankle-brachial index of 0.5 on preadmission noninvasive assessment was recorded via a contralateral approach after sterile prepping and draping of the patient, administration of conscious sedation, the infiltration of local anesthetic (usually lidocaine 1% or 2% solution) at the right femoral access site, placement of an arterial sheath in the femoral artery, and advancement of the contra guide catheter over 0.035-in guidewire under fluoroscopic guidance. The tip of the guide catheter is taken beyond the aortobifemoral junction and positioned into the right iliac artery. An angiogram (as shown) is obtained after the guidewire is removed. The proximal end of the catheter is connected to a manifold and 4-8 mL of contrast agent is manually injected during cineangiographic recording. The image may be played in a loop, or a particular frame may be saved for use as a roadmap during angioplasty. Intravenous antithrombin agent, usually heparin, is administered as a bolus (generally 3000-4000 IU) before angioplasty. The patient's activated clotting time is monitored, with continuous monitoring of intra-arterial pressure, pulse oximetry, and heart rate.
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Once the initial diagnostic angiogram is obtained for use as a roadmap, a 0.018-in guidewire is introduced into the side opening of a Y-connector (attached to the manifold at one end and the proximal end of the guide catheter at the other). A small torque device is used over the proximal end of the guidewire for steering purposes, while a small terminal bend is created by hand over the distal end of the guidewire before introducing it into the guide catheter. The wire is advanced through the 6F contra guide across the stenosis in the proximal segment of the left superficial femoral artery. The passage of the guidewire is monitored with fluoroscopy and by injecting small amounts of contrast agent. Occasionally, a combination of torque and forward pressure is required to cross the lesion. In tight lesions, the balloon catheter is sometimes advanced as well and used as support for guidewire passage.An angioplasty balloon is prepared by connecting its proximal port to an inflating device that contains a half-and-half imaging contrast agent and sterile saline solution. Negative pressure is applied to extrude any air bubbles. The inflating device is left in negative pressure during advancement of the balloon with one hand over the guidewire, which is held with the other hand. The balloon is advanced beyond the distal end of the guide catheter and straddled across the stenosed segment. A small amount of contrast agent is injected in order to confirm proper positioning of the balloon. The balloon is inflated by dialing up the pressure with the inflation device to several atmospheres (bars), usually 4-8 bars. The mixed contrast and saline solution contained in the inflation device moves gradually into the balloon as a result of the increasing pressure; as the balloon expands, it becomes visible under fluoroscopy (as shown). The balloon is left in the inflated position for several seconds to exert circumferential pressure on the stenosed arterial segment and expand the luminal dimension. The balloon is deflated by drawing negative pressure through the inflation device. Once deflated, it is gradually pulled back into the guide catheter while the wire is retained across the lesion.
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Angiogram obtained after percutaneous transluminal angioplasty of the left superficial femoral artery (SFA) shows improvement in the luminal diameter at the stenosed segment; however, it still appears to be at least 70% narrowed, with linear dissection. To patch the dissection, a stent-balloon catheter is prepared similar to the balloon catheter, except that, prior to insertion into the guide catheter, no negative pressure is applied. The stent catheter is then advanced over the guidewire through the guide catheter beyond its distal end and taken across the lesion. The stent is positioned over the dissection by injecting a small amount of contrast material through the guide to confirm its proper positioning and cover the entire dissected segment. The stent is deployed by first drawing negative pressure in the stent balloon and, subsequently, inflating it by injecting the contrast-saline solution through the inflation device. The stent is left inflated for several seconds at 5-10 bars of pressure. The stent-balloon is then deflated and withdrawn, while retaining the guidewire across the lesion. A poststenting angiogram is obtained.
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Poststenting angiogram obtained after withdrawal of the guidewire, which is done after confirming the absence of any flap, dissection, or filling defect. Image shows residual stenosis in the left superficial femoral artery (SFA) to be 0%. The guide catheter is finally withdrawn. The right femoral access site that provided contralateral approach to the left SFA stenosis is sealed with a percutaneous closure device.
