Infrapopliteal Disease




INTRODUCTION



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Infrapopliteal (IP) peripheral arterial disease (PAD) often occurs as part of multilevel atherosclerotic disease and is more commonly seen in patients with long-standing diabetes mellitus, patients with chronic kidney disease, or the elderly.1 Presence of moderate stenosis with 1 or 2 critical lesions can disrupt pulsatile flow to the limb. Chronic stable limb ischemia is predominantly asymptomatic, with a minority (20%) of patients complaining of symptoms of claudication. Rest pain and/or tissue necrosis occurs (Figure 36-1) when the compensatory mechanisms that were developed in absence of straight line flow, such as ischemic preconditioning of the limb and development of the collaterals, are no longer capable to meeting the oxygen demands.2 The arterial tree below the knee has relatively smaller-caliber vessels that in this population are often calcified, and stenotic lesions are rather diffuse (Figure 36-2).




Figure 36-1


Ulcer at the base of the second toe. Note the pale base with very pale margins and clearly demarcated margins.






Figure 36-2


Below-the-knee arteries of a patient with critical limb ischemia. Note that the posterior tibial artery is totally occluded, the peroneal artery occludes shortly after it originated, and the anterior tibial artery has multiple tandem lesions followed by total blockage. Ant., anterior.





Open vascular repair has been the mainstay of treatment, but given the significant comorbidities and lack of viable distal bypass target, endovascular approach is typically considered first. Patients who do have a patent artery that provides direct flow to the foot without other major comorbid conditions and have good vein conduit for bypass should be considered for surgical bypass. Patients with limited life expectancy and extensive gangrene or necrosis should undergo primary amputation.



Patients with IP disease in conjunction with femoral-popliteal disease have a lower risk for amputation and have longer amputation-free survival when compared with patients who have IP disease only.3 Patients who will benefit from revascularization include patients with Rutherford categories 4 to 6, systolic ankle pressure <50 mm Hg, nonpulsatile plethysmographic tracing, and/or transcutaneous oxygen pressure <30 mm Hg.4,5 Clinically, patients present with limb pain at rest, nonhealing ischemic ulceration, or gangrene. The pain is usually located in the acral portion of the leg, toes, or heels and is severe and persistent. The feet may be insensitive to cold, joints may be stiff, and patients may suffer from hyperesthesia. Patients may complain of pain relief when feet are in dependent position, and conversely, pain may increase if feet are above the level of heart or even when laying in bed with feet at heart level. Patients will often narrate how they have pain in the feet at night that gets better when they hang the feet over the side of the bed. During a clinic visit, one may be deceived by rubor that is ­typically present when patients remove their shoes, but it is important to stress that this “dependent rubor” (Figure 36-3) is matched by “elevation pallor” (Buerger sign) (Figure 36-4). Sometimes, the initial presentation will be gangrene or a wound, as is the case in ­people with advanced diabetes mellitus and associated ­neuropathy. It is important to know that this particular patient subset may not have rest pain due to neuropathy. Incorporation of handheld Doppler in the clinic can help the clinician to estimate presence of blood flow at various levels in the foot. Doppler signals from ­dorsalis pedis can be picked up at the level of ankle crease (Figure 36-5), and one could follow the course of the dorsalis pedis right to the deep plantar artery that lies between the first and second metatarsal bone (Figure 36-6). Similarly, the peroneal trunk can be heard in the ankle area (Figure 36-7) and can be followed into plantar arteries at least in the proximal area. In “thinner” legs, Doppler signals from the anterior tibial artery can also be picked up along the lateral border of the tibial boney prominence (Figure 36-8).




Figure 36-3


Leg elevation for about 2 seconds in this patient elicited numbness and pain in the foot, and pale skin can be appreciated.






Figure 36-4


Comparison of the leg in the same patient in elevated and dependent positions. Note the dependent rubor when the leg is left to hang down.






Figure 36-5


Dorsum of the ankle in the extended position is a good place to locate the dorsalis pedis pulse. With severely compromised blood flow, use a lot of gel and very light pressure to hear Doppler signals.






Figure 36-6


The deep plantar artery can be heard with Doppler in the web between the first and second toe, and sometime when the dorsalis pedis artery cannot be heard, it may be a good idea to place the probe in this location and trace the dorsalis pedis toward the ankle.






Figure 36-7


The posterior tibial artery can be difficult to locate, and holding the Doppler probe at an angle may help. This maneuver is also helpful in edematous or large ankles.






Figure 36-8


The anterior tibial artery can be heard with Doppler along the tibial boney prominence. It sometimes help to “rock” the Doppler transducer back and forth while in the longitudinal plane. It may require a little bit of pressure to hear the artery with Doppler because it could be deep and not as readily audible as the dorsalis pedis or posterior tibial arteries.






ANATOMY



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A thorough knowledge of the arterial tree and its surface projections below the knee including the foot is of paramount importance for possible revascularization. The popliteal artery courses along the posterior surface of the femur and tibia. It divides into 2 branches just below the proximal anastomosis of the fibula to the tibia, giving rise to an anterior tibial artery and a tibial peroneal trunk (Figure 36-9). The anterior tibial artery pierces the interosseus membrane between the tibia and the fibula and courses along the anterior surface of the interosseus membrane close to the tibia, where it changes at the ankle joint and becomes the dorsalis pedis artery (Figure 36-10). Lateral and medial malleolar branches can form interconnections between the anterior and posterior tibial arteries and the peroneal artery as a form of collateral circulation when there is a stenotic lesion. The dorsalis pedis terminates as the deep plantar artery, which enters the sole of the foot to join the lateral plantar artery to form the plantar arch (passes between 2 heads of first dorsal interosseous muscle) (Figure 36-11).




Figure 36-9


Digital subtraction image of popliteal artery dividing into anterior tibial artery and tibioperoneal trunk. The tibioperoneal trunk can further be seen dividing into the peroneal artery and posterior tibial artery. In anteroposterior view, the peroneal artery is typically in the middle. Geniculate branches of the popliteal artery can also be seen arising from the popliteal artery. Geniculate branches provide important collateral pathway in times of popliteal, tibioperoneal, or proximal posterior tibial artery occlusion. They typically restore blood flow to the mid-distal posterior tibial artery.






Figure 36-10


The anterior tibial artery can be seen coursing along the lateral side of the tibia. Doppler signals can be heard along the tibial crest.




Jan 2, 2019 | Posted by in CARDIOLOGY | Comments Off on Infrapopliteal Disease
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