Peripheral Arterial Disease



Peripheral Arterial Disease


Joseph J. Ingrassia

Matt Finn

Sahil Parikh



INTRODUCTION


Epidemiology

The Centers for Disease Control and Prevention (CDC) estimates that around 8.5 million Americans suffer from peripheral arterial disease (PAD).1 Some estimate that the true prevalence of PAD in the United States is closer to 20 million and is expected to increase in the coming years as the population ages.2 Up to one-third of patients above the age of 50 years with either diabetes or smoking history or above the age of 70 years are afflicted with PAD.3 The disparate estimates regarding the prevalence of PAD likely represent a combination of a lack of awareness in the medical community and asymptomatic or atypical presentation of the disease in patients.4


Risk Factors

Common atherosclerotic risk factors such as age, hypertension, hyperlipidemia, diabetes mellitus (DM), and smoking contribute to the risk of developing lower extremity PAD.5

Smoking, particularly, is a powerful risk factor for PAD development.6 Depending on the measurements used, smoking contributes to 1.9 to 3.4 times increased risk for the odds of the development of PAD.7 Among U.S. male professionals, smoking is the most contributable risk factor for the occurrence of PAD.8 Chronic kidney disease9 is associated with incident PAD and worse clinical outcomes. African American race10 even after adjustment for multiple risk factors, including inflammatory markers, had an odds ratio of 1.7 to 2.9 for PAD compared to non-Hispanic whites.11

DM that is poorly controlled and/or longstanding is associated with the development of PAD, whereas new-onset diabetes is not as strongly associated.12 Patients with PAD who have DM are more likely to have an amputation and are at an increased risk of mortality compared to patients who are non-DM with PAD.13

Hyperlipidemia is closely linked with PAD; however, compared with healthy controls patients with PAD have been found to have lower levels of high-density lipoprotein (HDL) with higher concentrations of very low-density lipoprotein (vLDL) and triglycerides. Interestingly, the levels of LDL were lower in patients with established PAD compared with healthy controls.14 Reasons for these findings are not fully elucidated, but the complex interplay between both biologic and mechanical forces acting on the lower extremity vasculature may partially explain why the protective effect of HDL seems to be more important than is low-density lipoprotein (LDL) elevation in the development of PAD.

Different risk factors may predispose patients to different anatomic presentations of PAD, with male gender and cigarette smoking associated with higher incidence of iliac disease, whereas older age and diabetes are associated more with the development of tibial level disease.15


PATHOGENESIS

PAD is a spectrum of disease that is the result of progressive arterial insufficiency most commonly because of atherosclerosis. In addition to the traditional mechanisms of progression of atherosclerosis, the lower extremity arteries, specifically the superficial femoral artery, are subject to mechanical forces that promote the progression of atherosclerosis16 (Table 80.1).

In patients with chronic limb-threatening ischemia (CLTI), progressive luminal narrowing may not be the only or most important factor in the development of ischemia. Postmortem study indicates that thrombotic occlusion with insignificant atherosclerotic changes of the affected vessels is seen in a significant portion of limbs with CLTI.17 This supports a mechanism of chronic subclinical atheroembolism leading to progressive arterial insufficiency. Traditionally, large thromboembolic causes of acute arterial occlusion and/or insufficiency from causes such as atrial fibrillation, paradoxical embolism, endocarditis, and/or thromboembolism from aneurysms more proximally typically present acutely as acute limb ischemia and represent medical emergencies.


CLINICAL PRESENTATION


Acute Limb Ischemia

Acute limb ischemia is most often due to arterial thromboembolism. In patients without preexisting PAD, there is an abrupt onset of symptoms. Pain in the affected leg distal to the occlusion, paresthesias, and/or paralysis or diminished motor function are common complaints in patients with acute limb ischemia.

Patients with preexisting PAD may have developed sufficient arterial collateralization that acute limb ischemia may present as a sudden worsening of preexisting symptoms.

Clinical presentation and physical examination of patients with acute limb ischemia are often remembered by the “Six P’s”: painful and pale limb distal to the level of occlusion,

with diminished or absent pulses that can eventually progress to poikilothermia, paresthesias, and paralysis if left untreated. Therapy for this condition includes prompt revascularization if the limb is deemed viable and amputation for nonviable limbs. The Rutherford Classification of acute limb ischemia is presented in Table 80.2.21 Consultation with a vascular specialist is recommended in all cases of suspected acute limb ischemia.
















Chronic Limb Ischemia: Intermittent Claudication to Chronic Limb-Threatening Ischemia

Patients with arterial insufficiency of the lower extremities present with claudication symptoms distal to the hemodynamically significant lesion. Aortoiliac disease may present with exertional cramping of the buttocks and thighs as well as impotence and atrophy of the musculature in the lower limbs (Leriche syndrome). Disease in the common and superficial femoral arteries presents with claudication in the calves (typical intermittent claudication). Isolated tibial level disease typically does not produce symptoms of claudication.

Most patients with PAD, however, do not present with typical claudication symptoms.3 Patients with established vascular disease in one territory (coronary, cerebrovascular) or those who are at high risk for atherosclerotic vascular disease should be questioned closely regarding atypical manifestations of lower extremity PAD. These symptoms may include muscle groups that are easily fatigued out of proportion to the level of activity, aching and/or tingling that are exacerbated by exertion and relieved with rest, fatigue with periods of prolonged standing, etc.

Physical examination of the patient with chronic ischemia of the lower extremities may reveal loss of hair over the lower legs and feet; pale, shiny, and/or atrophic skin; disturbances in nail growth; elevation pallor; dependent rubor progressing to minor tissue loss; and/or frank gangrene.

Patients that are classified within Rutherford Classes 4 to 6 for more than 2 weeks with an additional abnormal hemodynamic parameter (ankle-brachial index [ABI] < 0.4, absolute highest ankle systolic pressure <50 mm Hg, absolute toe pressure <30 mm Hg, transcutaneous oximetry [TcPO2] < 30 mm Hg, and/or flat or minimally pulsatile pulse volume recording) are deemed to have critical limb ischemia (CLI) or CLTI.22 Table 80.3 outlines commonly used classification systems for patients with chronic limb ischemia.21,23








Patients with claudication are at an increased risk of cardiovascular-related morbidity and mortality. Some datasets show PAD is associated with hazard ratios above six for related cardiovascular disease morbidity and mortality.7

Specifically, regarding the risk of future limb events, 21% of patients with intermittent claudication progress to CLTI within 5 years,24 making the identification and early medical management of these patients of paramount importance.



Aneurysmal Disease

Aneurysmal disease is defined as a focal dilation that is increased greater than 50% of the vessel’s normal reference diameter involving all components of the vessel wall (intima, media, and adventitia).


Iliac Artery Aneurysms

Isolated iliac artery aneurysms are rare. More commonly, iliac artery aneurysms are associated with abdominal aortic aneurysms (AAAs), and the management of iliac artery aneurysms is dependent on the management of the AAA. In cases where the common iliac artery aneurysm is larger than 1.6 cm in diameter, the iliac aneurysm should be followed independently from the AAA. Repair is indicated for symptomatic iliac aneurysms, aneurysms greater than 3 cm in diameter, those that expand greater than or equal to 7 mm in 6 months or greater than 1 cm in 1 year.25 For patients with concomitant AAA, any common iliac artery aneurysm is treated in order to assure a proper seal. In isolated iliac artery aneurysm, consideration of the location of internal iliac artery with respect to the aneurysm must be given as this may impact the endovascular treatment options.


Popliteal Artery Aneurysms

Popliteal aneurysms are the most common type of aneurysm in the lower extremity. There is a strong male prevalence, and it occurs most commonly in the fifth and sixth decades. Typically, popliteal aneurysms are detected incidentally on imaging testing and are strongly associated with atherosclerotic disease. Symptoms range from an asymptomatic pulsatile mass to limb ischemia from thromboembolism. Thromboembolism is more common in larger aneurysms (>2 cm). Patients with popliteal artery aneurysms are at high risk for aneurysm formation in the contralateral limb, femoral arteries, and abdominal aorta. These areas should be screened with vascular imaging when a popliteal artery aneurysm is detected. Repair is indicated for symptomatic aneurysms of any size, especially patent aneurysms greater than 2 cm in diameter26 given the increased risk of limb ischemia or those that have expanded >0.5 cm per year. Thrombus within the aneurysm sac may be a relative indication for repair. Open surgical or endovascular repair with a covered stent may be undertaken. Given the anatomic location behind the knee and relatively straightforward open surgical approach, surgical excision is preferred in patients who are candidates for both approaches.

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May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Peripheral Arterial Disease

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