Arterial Macroembolism

Diagnosis and Anatomy

Arterial macroembolism is most commonly from a cardiac source. This is typically observed in a patient who has atrial fibrillation with left atrial thrombus or after a myocardial infarction with left ventricular thrombus. Common locations of embolic lodgment are at arterial bifurcations where the artery caliber changes, such as the aortic bifurcation (∼35%), femoral bifurcation (∼50%), or popliteal artery (∼12%).

The diagnosis is made with combination of history and physical examination findings. The classic findings are the six P s: pain, pulselessness, poikliothermia, pallor, paresthesias, and paralysis. Often, the location of the embolism can be determined by physical examination. For example, a new-onset atrial fibrillation, right-leg ALI, nonpalpable right femoral pulse, and normal left lower extremity pulse suggests thromboembolism in the iliac artery. Conversely, an aged patient who has long-standing arterial atherosclerotic disease and claudication and who presents with a cool right leg, a weakly palpable femoral pulse, and only Doppler signals in the contralateral nonaffected side probably does not have an embolic etiology causing the limb ischemia. Other nonembolic etiologies of ALI include in-situ arterial thrombosis, peripheral bypass thrombosis, peripheral arterial aneurysms, trauma (popliteal artery disruption or penetrating injury), or acute aortic dissection with occlusion of the aorta or iliac arteries.

Men and women are equally affected by ALI. Modern series amputation rates are 13%, mortality is approximately 10%, and the average hospital length of stay is approximately 10 days. Generally, ALI does not occur in young people outside of trauma. In young patients it may be a result of unusual circumstances such as paradoxical emboli or hypercoagulable disorders, or it occurs in those with severe early-onset cardiac disease.

Excellent judgment is needed in the assessment of late grade 3 limb ischemia. It is important not to attempt limb salvage in those with nonrecoverable ischemia, because the tissue is not viable. If an examination suggests marginal viability, revascularization with reassessment of tissue viability is reasonable, with close observation and a low threshold to amputate if dictated by clinical status. A discussion with the patient and the patient’s family is important, given the high potential for limb loss.

Two primary factors underlie the morbidity and mortality that results from ALI, namely, the patient’s underlying comorbid illness and a delay in recognition and revascularization. Not surprisingly, skin mottling and rest pain are associated with increased risk of amputation. Another study suggested that ALI-related mortality was increased with delay in treatment of ischemia, significant underlying atherosclerosis, and poor arterial backbleeding at operation. Other factors associated with decreased amputation-free survival include ethnicity other than European, older age, a history of neurologic disease, malignancy, congestive heart failure, and low body weight.

Choosing the appropriate therapy is also an important factor to decrease amputation occurrence and mortality ( Figure 1 ). Although strong evidence suggests equivalence of endovascular or open surgical therapies, in terms of mortality and amputation, the etiology of the ALI needs to be factored into this equation.

Two articles published in the 1990s suggested that thrombolytic therapy had equivalent outcomes for surgical therapy in patients with ALI. These were the Surgery or Thrombolysis in Lower Extremity Ischemia (STILE) and Thrombolysis or Peripheral Artery Surgery (TOPAS) trials, which randomized patients to arteriography and thrombolytic therapy with urokinase, versus arteriography and embolectomy or urgent bypass. Although these data are robust, a majority of patients in both of these trials had Class I and IIA ischemia, and less than 25% had class IIB or III limb ischemia caused by arterial macroembolism.

A large national database study of patients with an embolic etiology (generally stage IIb ischemia) suggested that amputation was significantly less likely with embolectomy compared to thrombolytic therapy. Patients who failed thrombolytic therapy had a much greater risk of amputation and death than those primarily treated with embolectomy.