Peripheral artery disease
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</parsererror> peripheral arterial disease (defined as an ankle-brachial index of <0.9) >80% of patients with occlusive arterial disease are either former or current smokers.
Approximately one third of all deaths from occlusive arterial disease are secondary to metabolic complications upon revascularization
Reperfusion injury is characterized clinically by the presence of myoglobinemia, renal failure, and peripheral muscle infarction. The main laboratory abnormalities supporting this diagnosis include hyperkalemia, myoglobinemia, metabolic acidosis, and an elevation in creatinine kinase level.
In the lower limbs, thrombotic occlusion accounts for >80% of cases.
Atrial fibrillation is associated with at least two thirds of all peripheral emboli
blue toe syndrome
Patients with acute limb ischemia exhibit one or more of the "Six Ps": pain, pallor, paralysis, pulselessness, paresthesias, and polar (for cold). However, a lack of one or more of these findings does not exclude ischemia.
With vessel occlusion, severe, steady pain in the involved extremity associated with decreased skin temperature is expected. Hypoesthesia or hyperesthesia due to ischemic neuropathy is typically an early finding, as is muscle weakness. Two-point discrimination, vibratory sensation, and proprioception are often diminished prior to the loss of deep sensation. Absence of a palpable distal pulse is not a particularly helpful sign in a patient with long-standing vascular disease unless accompanied by skin changes compatible with acute arterial obstruction.
As ischemic injury progresses, anesthesia and paralysis become evident and foreshadow impending gangrene and the loss of limb viability. Preservation of light touch on skin testing is a good guide to tissue viability. A patient with an acute ischemic limb with signs of muscle paralysis, sensory loss, and prolonged ischemia has a limb that is likely nonviable.
he time limit for limb viability is dependent on the effectiveness of collateral circulation. Therefore, no arbitrary time period should be used to rule out treatment options.
Microemboli present clinically with pain and cyanosis in the involved digit, petechiae, and local muscle pain and tenderness at the site of infarction. Several different small areas can be affected with a shower of microemboli originating from a large or unstable source. Although mottling and decreased function may occur, pulses are preserved. See also Table 64-1 for symptoms of related disorders
Uncommon presentations of deep venous thrombosis, phlegmasia cerulea dolens (painful blue inflammation), and phlegmasia alba dolens, or milk leg, can also often be confused with obstructive arterial disease. In the former, the patient presents with an extremely swollen and cyanotic leg from venous engorgement due to massive iliofemoral thrombosis. This high-grade obstruction can compromise perfusion to the foot from high compartment pressures and lead to venous gangrene.12 Phlegmasia alba dolens, usually seen in association with pregnancy, is also due to massive iliofemoral thrombosis, but the patient's leg is pale or white secondary to associated arterial spasm. Dorsalis pedis and posterior tibial pulses may be diminished or absent, which can lead to a false diagnosis of arterial occlusion. The arterial spasm with milk leg is transient and often followed by venous engorgement, which suggests the correct diagnosis.
On physical examination, the skin and all peripheral pulses should be carefully evaluated. Shiny, hyperpigmented skin with hair loss and ulceration, thickened nails, muscle atrophy, vascular bruits, and poor pulses are the hallmark of chronic obstructive arterial disease. Whereas ulcers from venous insufficiency occur near the medial malleoli, arterial ulcers tend to occur on the foot and toes and are typically more painful.
At the bedside, decreased perfusion can be diagnosed by blanching the involved extremity with finger pressure and noting a delay in the return of blood compared with the uninvolved extremity; 2 to 3 seconds is considered normal. However, several factors can influence capillary refill, so one cannot rely on the presence or absence of this finding alone.
The ankle-brachial index is the ratio of the systolic blood pressure with the cuff just above the malleolus (with the Doppler probe over the posterior tibial or dorsalis pedis artery) to the highest brachial pressure in either arm (Figure 64-1). Patients with chronic obstructive arterial disease have an ankle-brachial index of <1.0. The ankle-brachial index can be calculated to help determine the severity of peripheral arterial disease. Values of <0.25 suggest potentially limb-threatening vascular disease, and consultation with a vascular surgeon in the ED may be of benefit despite absence of complete obstruction. An ankle-brachial index of >1.3 is likely secondary to a noncompressible vessel and may be seen in patients with severe vascular calcification
Patients with claudication typically have ankle-brachial index values ranging from 0.41 to 0.90, and those with critical leg ischemia have values <0.41.
duplex US of the suspected arterial system can detect an obstruction to flow. Duplex US is very accurate for detecting complete or incomplete obstruction in the common femoral, superficial femoral, and popliteal vessels, and in previous bypass grafts. Sensitivity declines for localization of thromboembolic occlusion at or below the calf level. Similarly, duplex US has high sensitivity for detecting obstruction in the axillary, subclavian, and brachial arteries.
CT (with contrast), which is the most readily available among these in most EDs, has a sensitivity similar to that of aortography.
Although no studies to date have established an unequivocally beneficial role of any generally administered antithrombotic agent for acute arterial occlusion, when the diagnosis of acute limb ischemia is known or suspected, the current practice is the immediate administration of IV unfractionated heparin. Weight-adjusted dosing of unfractionated heparin at an 80 units/kg bolus followed by an infusion of 18 units/kg/h rapidly achieves a therapeutic heparin level and activated partial thromboplastin time.
Supportive therapies, including the administration of analgesia and dependent positioning of the extremity, should not be overlooked. Fluid resuscitation and treatment of heart failure and dysrhythmias are sometimes necessary to improve limb perfusion.
Catheter-directed intra-arterial thrombolysis has replaced systemic thrombolysis for peripheral artery embolic or thrombotic disease.
The final recommendation is that catheter-directed thrombolysis should be considered a treatment option in patients with thrombotic or embolic disease of <14 days provided the patient is at low risk for myonecrosis or ischemic nerve damage during the time required to achieve reperfusion.1
The decision regarding the method of revascularization is a complex one.
PTA may be a better option for patients with multiple comorbidities who are at higher risk when undergoing major surgery and for those with a short life expectancy. In general, open surgery seems to be a more attractive option for patients with inflow disease and multifocal and long-segment disease. Open surgery still is the gold standard therapy and an important treatment option for patients with a favorable long-term prognosis.
The American College of Cardiology/American Heart Association 2005 guidelines included cilostazol, a phosphodiesterase inhibitor, as a Class I recommendation for the treatment of claudication in patients with obstructive arterial disease2 (avoid in patients with heart failure). Pentoxifylline is considered a second-line therapy for the treatment of claudication (Class IIb)