Small-Vessel Syndrome

Cutaneous ischemia or local areas of cyanosis or necrosis in a hand or foot that generally has adequate circulation.

In the elderly, ischemia in a hand or foot that has palpable pulses may be due to cryoglobulinemia, cryofibrinogenemia, disseminated intravascular coagulation, essential thrombocytosis, polycythemia, vasculitis secondary to drug-induced systemic lupus erythematosus, the phospholipid (anticardiolipin antibody) syndrome, scleroderma, or emboli from an arterial aneurysm, the heart, or atherosclerotic plaques.

Symptoms, Signs, and Diagnosis

Patients usually present with a cyanotic or gangrenous digit and may have many small lesions on several extremities. Occasionally, cyanosis or dependent rubor affects an entire foot or hand.

In patients with peripheral atherosclerosis and pulseless limbs, sudden worsening of cutaneous ischemia or development of localized cyanosis or necrosis in an otherwise adequately perfused hand or foot may indicate small-vessel syndrome. In such cases, evaluation of the hand is particularly important because severe ischemia is uncommon in the upper extremities, even if atherosclerosis is advanced.

The history and physical examination may provide clues to the cause (see Table 93-1). The physical examination should include a search for abdominal, femoropopliteal, and subclavian aneurysms. Popliteal aneurysms shed small emboli and should be considered if ischemia is confined to one foot.

Laboratory evaluation should include a CBC, a platelet count, coagulation screening, and tests for cryoproteins, antinuclear antibodies, lupus anticoagulant, and anticardiolipin antibodies. Lupus anticoagulant, a misnomer, occurs in only 10% of patients with systemic lupus erythematous. In vitro, this anticoagulant and other anticardiolipin antibodies interfere with phospholipid-dependent coagulation tests (eg, partial thromboplastin time) by binding to phospholipids that accelerate the activation of prothrombin by factor Xa. Paradoxically, they cause thrombosis in vivo. An elevated anticardiolipin antibody level or the presence of lupus anticoagulant indicates the antiphospholipid antibody syndrome. Administering normal plasma to such patients does not correct the defect; venous and small arterial thrombi occur in 27% of patients with the lupus anticoagulant.

ECG is indicated if mitral valve disease or ventricular aneurysm is suspected, and ultrasonography of the aorta and popliteal arteries may be necessary to rule out an aneurysm. The diagnosis of atheromatous emboli (due to fracturing of plaques) is reached by exclusion. Occasionally, atheromatous emboli manifest as livedo reticularis (a lacy network of cyanotic-looking superficial vessels on the anterior side of the leg).

Treatment

Underlying disorders should be identified and managed. Aneurysms must be surgically repaired. Long-term anticoagulation therapy with warfarin is indicated for patients with cardiac embolism; antiplatelet drugs, including aspirin, are indicated for patients with atheromatous emboli. Appropriate therapy for patients with the phospholipid syndrome is not established. Warfarin may be effective, but the international normalized ratio (INR) must be > 3.

For all patients with small-vessel syndrome, preventing dehydration, which can further compromise flow, is important.