Noninvasive Diagnostic Testing

Measuring the ankle-brachial index (ABI) both at rest and after exercise is very useful, especially in individuals who have risk factors for PAD. Resting ABI may be insensitive for detecting mild aorto-iliac occlusive disease and is not designed to define the degree of functional limitation. However, it establishes the diagnosis of PAD and identifies a population at high risk of cardiovascular ischemic events. Incompressible arteries (elderly patients, patients with diabetes, renal failure) make such rest testing difficult. The toe-brachial index (TBI) should be used in individuals with noncompressible pedal pulses. Exercise ABI may be even more useful than resting ABI as this will “unmask” PAD when resting the ABI is normal. Performing segmental ABI and pulse volume recordings together with the ABI can indicate presence of multilevel occlusive lower extremity PAD.

Duplex ultrasound of the extremities is useful to diagnose the anatomic location and degree of stenosis of PAD. This type of study is recommended for routine surveillance after femoral-popliteal or femoral-tibial-pedal bypass.

Other noninvasive testing includes magnetic resonance angiography (MRA) and computed tomographic angiography (CTA). MRA of the extremities is useful to diagnose the anatomic location and degree of stenosis of PAD. The MRA should be performed with gadolinium administration. It must be noted, however, that gadolinium use in individuals with an estimated glomerular filtration rate (eGFR) less than 60 ml/min has been associated with nephrogenic systemic fibrosis (NSF)/nephrogenic fibrosing dermopathy. MRA of the extremities is useful in selecting patients with lower extremity PAD as candidates for endovascular intervention.

CTA of the extremities may be considered to diagnose the anatomic location and presence of significant stenosis in patients with lower extremity PAD. CTA may be considered as a substitute for MRA for those patients with contraindications to MRA (claustrophobia, presence of pacemaker/implantable cardioverter-defibrillator).

Peripheral Vascular Angiography

Peripheral vascular angiography, both as a diagnostic tool and for aiding percutaneous vascular intervention, is not difficult once techniques of coronary angiography have been mastered. Angiography is usually performed after completion of noninvasive PAD screening tests (Fig 5-1).

Figure 5-1 Schematic diagram of the iliac (A) and femoral arterial systems (B).

Digital subtraction angiography (DSA) is the method of choice for identifying PAD. Standard cineangiography can also provide useful and satisfactory information. In addition, when performing angiography (especially abdominal aortography), it is possible to use dilute contrast, carbon dioxide, or gadolinium if the use of iodinated contrast is not clinically feasible.

Endovascular Percutaneous, Catheter-Based Revascularization Techniques

Endovascular revascularization techniques have greatly advanced the management of obstructive PAD. Endovascular therapy offers several distinct advantages over surgical revascularization. The morbidity and mortality from endovascular therapy is low when compared with surgical revascularization. Unlike vascular surgery patients, these individuals often return to normal activity within 24to 48 hours of an uncomplicated procedure. Finally, endovascular therapies may be repeated if necessary, generally without increased difficulty or increased patient risk compared with the first procedure. Prior angioplasty does not preclude surgery if required later. The problems and complications associated with endovascular intervention are generally related to bleeding and vascular access.

Endovascular reconstruction options include the following:

The advantages of using percutaneous interventional procedures over bypass surgery (especially to treat chronic limb ischemia) include the following:

The efficacy of PTA versus stents for lower extremity arterial stenosis has not been demonstrated in randomized trials. PTA of distal abdominal lesions is effective; however, PTA followed by stenting offers greater advantages of larger vessel lumen gain, long-term patency (>70% at 5 years), high procedural success rates (90%), and less thromboembolism. Factors associated with a poor outcome with endovascular therapy include the following:

Iliac Artery Intervention

Iliac artery provides blood flow to the lower extremities, and permits access to the central circulation for coronary artery intervention, insertion of an intra-aortic balloon pump, other cardiac output assist devices, or treatment of vascular access site complications.

The indication to perform iliac artery intervention includes vascular access and symptomatic lower extremity ischemia. Iliac intervention may also be appropriate in patients with severe stenosis (Fig. 5-2, A and B) or occlusion of the femoropopliteal or infrapopliteal arteries and concomitant moderate iliac artery disease, in whom revascularizing the moderately stenosed iliac artery may improve the arterial inflow and lead to symptomatic improvement or salvage of the limb.

Figure 5-2 A, Totally occluded right iliac artery. B, Right iliac artery after successful angioplasty and stenting.

The indications for revascularization in the patient with intermittent claudication are as follows:

Endovascular treatment of significant iliac artery stenosis with claudication is indicated as follows:

Femoropopliteal Artery Intervention

Atherosclerotic occlusive disease is more common in the femoropopliteal artery than in the iliac artery. When the femoropopliteal artery is involved in a symptomatic lower extremity, complete occlusions are three times more frequent than stenosis. Table 5-4 demonstrates the morphologic stratification of femoropopliteal lesions according to the Transatlantic Inter-Society Consensus (TASC). According to the TASC recommendations, endovascular therapy is the treatment of choice for type A femoropopliteal lesions and surgery is the treatment of choice for type D lesions. Endovascular treatment is the preferred treatment for type B lesions and surgery is the preferred treatment for low risk patients with type C lesions. The patient’s comorbidities, fully informed patient preference, and the local operator’s long-term success rates must be considered when making these treatment recommendations for type B and type C lesions.

Table 5-4 Morphologic Stratification of Femoropopliteal Lesions

Endovascular interventions for TASC type A femoropopliteal arterial lesions have excellent procedural success and reported patency rates that vary from 30% to 80% at 1 year. The role of primary stenting for femoropopliteal disease remains incompletely defined. Stents (and other adjunctive techniques such as lasers, cutting balloons, atherectomy devices, and thermal cryoplasty devices) can be useful in the femoral, popliteal, and tibial arteries as salvage therapy for a suboptimal or failed result from balloon dilation (e.g., persistent translesional gradient, residual diameter stenosis greater than 50%, or flow-limiting dissection). The effectiveness of stents, atherectomy, cutting balloons, thermal devices, and lasers for the treatment of femoral-popliteal arterial lesions beyond this context is not well established (Figs. 5-3, 5-4, and 5-5).

Figure 5-3 Right superficial femoral artery (SFA) with significant serial stenosis.

Figure 5-4 Atherectomy of superficial femoral artery (SFA) plaque (some in caught in distal protection device/basket).

Figure 5-5 Postatherectomy angiogram of right superficial femoral artery (SFA).

Revascularization of the femoral or popliteal arteries is reserved for patients with lifestyle-limiting claudication, ischemic rest pain, and limb-threatening ischemia. Treatment of short (<5 cm) occlusions yields better results than treatment of long (>10 cm) occlusions or stenosis. The presence of patent runoff vessels correlates with long-term benefits, reflected in the improved outcome in patients with milder symptoms. Significant residual stenosis after angioplasty correlates with a poor long-term outcome, whereas the absence of diabetes correlates with an improved patency rate. Endovascular intervention is not indicated if there is no significant pressure gradient across a stenosis despite flow augmentation with vasodilators. Primary stent placement is not recommended in the femoral, popliteal, or tibial arteries (Figs. 5-6 and 5-7). Endovascular intervention is not indicated as prophylactic therapy in an asymptomatic patient with lower extremity PAD.

Figure 5-6 Popliteal artery stenosis.

Figure 5-7 Postangioplasty angiogram of popliteal artery.

Below-Knee Intervention

The traditional indication for infrapopliteal angioplasty has been limb salvage (ischemic rest pain and ischemic ulceration or gangrene). However, infrapopliteal angioplasty for severe claudication that prevents ambulation and for patients with moderate to severe claudication to increase the durability and effectiveness of femoropopliteal angioplasty has been advocated. Below-knee angioplasty has led to a dramatic decrease in the amputation rate. Balloon angioplasty of the infrapopliteal vessels is an effective technique for treating patients with distal atherosclerotic occlusive disease. It has been used mainly in patients with limb-threatening ischemia and multisegment disease. Appropriate anatomic selection is a key factor to maximize the benefit of this technique. In specific cases, below knee stent-supported angioplasty is also plausible.

Vascular Access

Familiarity with a variety of vascular access sites and techniques is one of the most important components of one’s basic skills in peripheral vascular intervention. Successful endovascular intervention requires the appropriate choice of vascular access. In most cases, access is obtained using a 21-gauge needle and 0.18-inch wire (4 F micropuncture set). The retrograde approach to the common femoral artery (CFA) is the most often used vascular access. Evaluation of the peripheral lower extremity disease requires identification of iliac bifurcation and common femoral artery patency (Fig. 5-8

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