The term subacute ischemia generally describes a clinical situation in which chronic ischemia is exacerbated by 1 or more factors, such as atherosclerosis, which then leads to acute ischemia. This is distinct from chronic ischemia, in which mild symptoms develop over a long period of time such that there is no immediate danger of tissue loss, and acute ischemia, in which tissue loss will occur if blood flow is not restored within hours. In our case report, the patient had a chronic occlusion of his ulnar artery secondary to trauma. Progression of atherosclerosis in his hand eventually led to critical ischemia and tissue loss.
The initial treatment for digital ischemia depends on the etiology. Patients presenting with exaggerated digital vasospasm (as in Raynaud's phenomenon) can be treated with calcium channel blockers or, more recently, with botulinum toxin type A (BTX-A).4
Other medical management has traditionally involved β-blockers, antiplatelet therapy, thermal biofeedback, and avoiding tobacco and alcohol consumption. Acute embolism is treated with thrombectomy. Additional management of these patients includes management of the underlying cause. Emboli from the heart can arise from arrhythmia or mechanical valves, and these can be treated with systemic anticoagulants. Atheroembolism can also be treated with intravascular stents.
Arterial reconstruction should be considered for patients with ischemia and tissue loss that signals that digital amputation is imminent if increased perfusion is not achieved.5,6
Microsurgical reconstruction for the upper limbs has historically received little attention despite the numerous similarities that exist between upper and lower extremity ischemia.2,7
Only a few have attempted to explore the subject, starting with Garret et al8
Prior to the adaptation of cardiac bypass grafting techniques for peripheral revascularization, the standard protocol for treating digital ischemia was simple resection of the occluded segment.6
The technique is still used to treat radial or ulnar artery aneurysms, but problems related to vessel tension across the wrist make this technique undesirable in patients with large areas of occlusion requiring excision.10
In 1989, Jones and Emerson6
described 14 chronically ischemic patients who underwent distal radial or ulnar artery revascularization. He found immediate postoperative improvement of symptoms in a majority of patients, although 5 grafts (35%) eventually thrombosed. Other more recent studies of reverse interpositional grafts involving resection of blocked arterial segments note long-term patency rates of 48%–100% at various follow-up intervals.11-14
The long-term success of these grafts depends on a number of factors. Dethmers and Houpt15
have documented a correlation between longer grafts and long-term occlusion. Similarly, Hughes et al2
found that patients revascularized for upper extremity ischemia caused by trauma had better outcomes than patients treated for atherosclerotic disease.
Recently, several examples of microsurgical bypass grafts that do not include excision of the diseased segment have been described.5,9,10
The reported benefits of leaving the occluded segment intact include an accompanying decrease in operative time and the ability to revascularize the hand without disrupting collateral flow. Katz and Kohl16
documented the outcomes of 32 patients treated for acute hand ischemia, reporting successful digital reperfusion in all patients and 100% graft patency at follow-ups from 6 months to 8 years. Despite the advantages of the bypass graft, however, aneurysmal arteries at the wrist may require resection because of the risk of embolization to the digital arteries.
The choice of graft ultimately depends on the availability of autologous conduit and the size of the vessel being bypassed. The saphenous and cephalic veins are currently the most frequently used autologous conduits for upper extremity bypass operations.1,3
Venous conduits are not limited by length, and saphenous veins generally have a more compatible diameter than cephalic veins.5
Where vessel length is not an issue, arteries can be ideal for interpositional or bypass grafting because they are structurally homologous to the affected vessels. Smith and colleagues17
found no evidence of intimal hyperplasia and 100% graft patency from 7 to 24 months in 3 patients with hypothenar hammer syndrome treated with a segment of the deep inferior epigastric artery. These conduits could thus be indicated in patients who may need additional procedures in the future, such as smokers or manual laborers who must continue to expose the hand to repetitive palmar trauma.
Given the relatively recent history of microsurgical reconstruction for digital ischemia, it will take time to assess the long-term success of interpositional and bypass grafts. Specifically, it will be important to determine the longevity of various types of grafts distal to the wrist, since the hand is particularly prone to trauma. Superficial grafts that cross the wrist will also need to be scrutinized for occlusion caused by flexion and extension. As expected, treatment options should be considered on the basis of the etiology and severity of the patient's ischemia. In carefully selected patients with subacute ischemia, microsurgical revascularization should be considered to prevent tissue loss.