Claudication: Peripheral Arterial Disease



Claudication


Peripheral Arterial Disease


Rebecca Madery and Nicole Strissel



Objectives



• Identify anatomic landmarks for proper vessel identification in the calf.


• Differentiate between various causes of arterial disease in the leg.


• State symptoms associated with arterial disease.


• Describe the duplex Doppler and indirect physiologic studies that can be used to detect arterial disease of the lower extremity.


• Describe the sonographic appearance of arterial disease in the lower extremity.


• Characterize Doppler waveforms associated with arterial disease.



CLINICAL SCENARIO


A 35-year-old man presents to the emergency department in mid-January in the upper Midwest. The patient complains of severe left foot pain, which is intermittently accompanied by numbness and tingling. The patient states he has experienced some leg pain during exercise over the past year but notes the pain is especially intense while he is resting, and the pain has progressed as the weather has grown colder. His pain is not relieved by over-the-counter pain medication. On physical examination, both feet display pallor, are cool to the touch, and have diminished pulses. The left fifth digit is also noted to have a small, painful sore, which he attributes to “breaking in new shoes.” The patient leads an active lifestyle and, aside from his feet, appears in overall good health. He admits to occasional alcohol use and smokes about one pack of cigarettes per day over the past 10 years.


A physiologic, noninvasive lower extremity arterial study is ordered. During the continuous wave Doppler examination, the vascular technologist notes biphasic signals in the common femoral artery, superficial femoral artery, and popliteal artery. Slightly reduced but patent flow is also detected in the posterior tibial artery at the medial malleolus. Distal phalanx flow studies do not demonstrate detectable arterial Doppler tracings in the left second, fourth, and fifth digits. The first and third distal phalanges demonstrate reduced, monophasic flow. Temperatures are 21° C in the second, fourth, and fifth digits with no postwarming increase. What is the most likely diagnosis?


This chapter describes various causes of arterial disease in the leg and the role of sonography and other vascular testing in diagnosing these diseases. Specific protocols may vary depending on the vascular laboratory. This chapter focuses on general protocols and expected Doppler waveforms associated with each disease. A brief explanation of normal anatomy is included, but the focus is on the pathology, waveforms, and risk factors that lead to arterial disease.


For the lower extremity, gray-scale, spectral, and color Doppler imaging and indirect physiologic testing are used to diagnose vascular causes of leg pain in the noninvasive vascular laboratory. Some of the arterial pathologies diagnosed sonographically include atherosclerosis obliterans (ASO), pseudoaneurysm, arteriovenous fistula (AVF), and compartment and entrapment syndromes.



Normal Vascular Anatomy


Lower extremity arteries are accompanied by a single vein or, distal to the popliteal artery, paired veins with the same name. Most of the anatomy can be well visualized on most patients with a 6 to 9 MHz linear transducer. Imaging of the distal aorta and iliac arteries requires the use of a curvilinear transducer with frequencies ranging from 3 to 6 MHz. Starting at the aortic bifurcation and working distally to the foot, a normal artery gradually tapers as it gives rise to branches until it terminates as an arteriole. The common iliac arteries originate at the level of the umbilicus from the aortic bifurcation and bifurcate into the external and internal (hypogastric) iliac arteries. The hypogastric artery branches deep into the pelvis to perfuse the sigmoid colon, rectum, and reproductive organs. The external iliac artery continues through the pelvis to become the common femoral artery at the inguinal canal, which bifurcates into the deep femoral artery (profunda) and femoral artery. At the level of the adductor canal, the femoral artery becomes the popliteal artery as it courses posterior to the knee and bifurcates into the anterior tibial artery and the tibioperoneal trunk. The anterior tibial artery branches anteriorly and laterally, passing through the space formed between the tibia and fibula then lateral to the tibial shaft where it eventually terminates on the dorsal side of the foot as the dorsalis pedis artery. The tibioperoneal trunk bifurcates into the posterior tibial artery and peroneal (fibular) artery. From a medial scanning approach, the posterior tibial artery continues more superficially than the peroneal artery, which runs deeper and lies just medial to the fibula. (Fig. 36-1; see Color Plate 55). Arteries of the ankle and foot commonly used for Doppler samples or pulses include the posterior tibial, which can be found about 1 inch posterior to the medial malleolus, and the dorsalis pedis, which is found in the anterior midfoot just over the proximal third metatarsal.


image
FIGURE 36-1 (A), Approach used to scan the left calf vessels. (B), Cross section of the calf vessels in relation to the tibia and fibula. From a medial approach, the posterior tibial artery is the most superficial, and the peroneal artery lies just above the fibula. Occasionally, the anterior tibial artery is visualized between the tibia and the fibula. (C), Sonographic cross-sectional (transverse) image of the calf vessels. Note the relationship of the vessels to the tibia and fibula (see Color Plate 55).


Symptoms and Testing


Claudication


Claudication, or intermittent claudication, is defined by repetitive cramping, aching, and pain a patient experiences, especially during exercise, with cessation of symptoms on rest. Typically, patients have a set distance they can travel before needing to stop and rest and then can continue with movement. If left untreated, this condition progresses to a severe condition known as rest pain. Symptoms of rest pain are similar to claudication and persist during periods of inactivity. Rest pain can be alleviated by placing the foot in a dependent position, which allows gravity to aid in distal limb perfusion (i.e., tilt the cart in a reverse Trendelenburg position when possible).


Claudication is caused by various factors. Arterial diseases include, but are not limited to, ASO, popliteal entrapment, arterial embolus, and aneurysmal disease. Other nonarterial causes that may mimic arterial disease include vein disease such as deep venous thrombosis, spine-related conditions, pulled muscles, tendinitis, trauma, fibromyalgia, and other musculoskeletal conditions.



Vascular Test Findings


Diagnostic examinations used in assessing lower limb arterial disease include physiologic nonimaging vascular studies (segmental pressures, ankle-brachial index [ABI], pulse volume recording [PVR]), sonography, computed tomography angiography, magnetic resonance angiography, and angiography. To include or rule out vascular claudication as a differential diagnosis, the first examination is typically a physiologic test involving continuous wave Doppler and segmental pressures before and after exercise. Using continuous wave Doppler, the patient should have a qualitative analysis of the common femoral artery, femoral artery, popliteal artery, posterior tibial artery, and dorsalis pedis artery to determine if the blood flow is triphasic, biphasic, or monophasic in nature (Fig. 36-2). To determine the approximate level of disease, segmental pressures and/or PVR’s should be taken. Normally, the pressure gradient between adjacent cuffs, or at the same level on the contralateral extremity, does not exceed 20 mm Hg. A pressure gradient greater than 30 mm Hg is indicative of a significant obstruction between or beneath the cuffs.1 Segmental pressures are taken by measuring blood pressures from the thigh, calf, and ankle (three-cuff method) and comparing that number with the highest brachial pressure (both arms should be assessed unless contraindicated). A four-cuff method may also be used with two cuffs placed on the thigh with the awareness that the cuff closest to the groin may be artificially elevated because of the discrepancy in cuff size and thigh circumference.


image
FIGURE 36-2 (A), Normal triphasic signal in the profunda femoris artery (PFA) of a healthy individual. (B), Biphasic tracing in the profunda femoris artery. The biphasic signal implies a loss of normal elasticity in the vessel wall, which is an early sign of atheromatous disease. (C), Monophasic tardus-parvus waveform seen in the popliteal artery (POP A) distal to a significant stenosis in the femoral artery.

An ABI can be used if a quick study is necessary or for follow-up of a prior physiologic test. A normal ABI ratio generally is 0.90 to 1.40. An ABI ratio less than 0.90 is considered abnormal; however, individuals with values between 0.90 and 1.10 and greater than 1.40 may be at a slightly higher risk for disease.1 After baseline values have been obtained, the patient should exercise (at the prescribed protocol of that vascular laboratory) and the ABI measurements should be repeated. Patients presenting with a normal ABI may unmask arterial disease after exercise due to the increased demand for blood in the working extremity. The ABI should increase or remain constant in a normal extremity. If pressures decrease significantly but return within 2 to 6 minutes, single-level disease should be considered. However, a significant decrease in pressures after exercise for 10 minutes is highly suggestive of multilevel disease. Symptoms of claudication are not likely to be vascular in origin if they do not correlate with a decrease in pressures.


If sonographic imaging is requested, assessment of the lower extremity arteries from the common femoral artery to the dorsalis pedis artery should be performed. Careful attention should be paid to the vessel walls in gray-scale and the flow patterns and waveforms in color and spectral Doppler imaging. Sonographic findings associated with arterial disease are discussed in further detail throughout the chapter.




Arterial Disease


Atherosclerosis


Peripheral arterial disease is the process in which arteries become narrowed and impede blood flow to the limbs, generally the lower extremities. Arteriosclerosis is a general term describing the hardening of arterial walls and the associated loss of elasticity. Arteriosclerosis results in a reduced arterial lumen and, ultimately, decreases blood pressure and flow to the distal limb or organ. A stenosis is considered hemodynamically significant if there is a 50% reduction in diameter or a 75% reduction in cross-sectional area.2 The most common cause of arteriosclerosis is atherosclerosis (ASO). ASO is the result of increased fatty deposits (atheromatous plaque) along the arterial walls. Patients may experience various symptoms depending on the severity of the disease ranging from asymptomatic to debilitating distal ulcerations and eventual limb loss.



Sonographic Findings


The sonographic appearance of ASO in both gray-scale and color Doppler imaging includes thickened arterial walls and a decreased vessel diameter secondary to atheromatous plaque bulging into the lumen. To support color and gray-scale findings, an angle-corrected spectral Doppler cursor should be placed proximal, at, and distal to the area of visual narrowing. It is generally accepted that a stenosis is hemodynamically significant if the peak systolic velocity doubles between a diseased segment and the normal area just proximal to the disease. Waveforms may show signs of spectral broadening and a loss of normal triphasic or biphasic flow patterns. In severe cases of claudication, arteries may be occluded. To demonstrate an occlusion sonographically, gray-scale imaging should show thrombus or calcified plaque within the arterial lumen, while color and spectral Doppler will demonstrate an absence of flow. Because of the confusing nature of collateral arteries that are typical in ASO cases, it is helpful to use the corresponding veins as landmarks when identifying the occluded arteries. It is necessary to document the absence or presence of flow below the occluded segment because it can change the possible treatment for the patient (i.e., a good distal arterial segment is needed for a bypass graft).



Popliteal Aneurysm


An aneurysm is a localized bulging or focal enlargement of a vessel by approximately 50%; the popliteal artery is the most common location for a peripheral aneurysm to occur.3 The accepted measurement criterion for a popliteal artery aneurysm is 1.5 to 2.0 cm. However, because the normal popliteal artery diameter measures from 0.4 to 0.9 cm, several studies suggest that, in correlation with an increased diameter of 50%, a focal area of 1.0 cm may be considered an aneurysm if the normal arterial diameter is 0.6 cm.3 Isolated aneurysms are rare in the iliac and femoral arteries. Lower extremity aneurysms increase the patient’s risk of having an abdominal aortic aneurysm. Close monitoring is necessary as significant risks are associated with lower extremity aneurysms including: distal embolization, acute occlusion and rupture.


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Aug 27, 2016 | Posted by in ULTRASONOGRAPHY | Comments Off on Claudication: Peripheral Arterial Disease

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