Arterial Thoracic Outlet Syndrome: A Case Study in How Relentless Its Complications Can Be

By Sean Lyden, MD

Presentation

In 2015, a 56-year-old woman was transferred to Cleveland Clinic for management of acute onset of left arm ischemia. Three-dimensional (3-D) CT-reconstructed imaging showed a left subclavian aneurysm with embolization, a rare and potentially dangerous complication of arterial thoracic outlet syndrome (Figure 1).

Figure 1. 3-D CT reconstruction at presentation showing the left subclavian aneurysm with embolization.

Initial interventions

Because of the embolic burden in the outflow of the arm and hand, the initial strategy was catheter-directed pharmacologic thrombolysis. We used a dual-level infusion for thrombolysis with tissue plasminogen activator (t-PA). Progress of the therapy was checked eight hours after initiation. Minimal progress of the lysis was noted, and there was significant residual clot burden in the arm, so mechanical thrombectomy was performed with the Possis AngioJet™ device.

After mechanical thrombectomy, several areas of stenosis were uncovered in brachial and radial arteries. These were treated with percutaneous transluminal angioplasty, which improved flow to the arm. The patient was kept on therapeutic anticoagulation with planned resection of the subclavian artery aneurysm.

A second ischemic event

Despite anticoagulation, rethrombosis of the brachial and axillary arteries occurred six hours later. The patient was returned to the operating room, where she underwent open thrombectomy of the arteries from a brachial cutdown and local instillation of t-PA into the radial and ulnar arteries to improve outflow. The forearm was noted to be tense. Clinically, compartment syndrome was present and was the likely etiology of the rethrombosis. This was treated with forearm fasciotomy and carpal tunnel release. The hand perfusion was markedly improved by the repeat operation.

Resection of ribs and aneurysm

Elevation of the subclavian artery over a cervical rib leads to local arterial trauma, aneurysmal formation with thrombus deposition, and embolization to the distal extremity. For this reason, surgical correction of the arterial thoracic outlet pathology was performed a few days later. This included resection of the left cervical and first rib, resection of the aneurysm and reconstruction with a left subclavian-to-axillary artery graft using the right femoral vein. The operation was notable for a very friable and small proximal subclavian artery just distal to the left vertebral.

Duplex ultrasonography before discharge and at six-month follow-up intervals during the first year showed a widely patent bypass and equal upper extremity brachial pressures.

A year later: Stenosis at proximal anastomosis

Although the patient had no symptoms, surveillance duplex ultrasonography after one year showed increased left subclavian artery velocities from 60 to 187 cm/s at the proximal anastomosis suggestive of a greater than 50 percent stenosis. Pulse volume recordings were consistent with new mildly dampened waveforms in the left arm, and a 10-mm Hg pressure drop was noted in the left brachial artery relative to the right. Findings were confirmed by CT angiography, and 3-D CT reconstruction clearly demonstrated a stenosis at the proximal anastomosis (Figure 2).

Figure 2. 3-D CT reconstruction demonstrating stenosis at the proximal anastomosis one year after initial presentation.

Weighing the treatment options

Multiple options were available to treat this problem. Surgical revision was an option, but the reoperative nature and the small friable subclavian artery at the original operation made this the least appealing approach. Endovascular revision, the minimally invasive approach, was appealing to the physicians and patient. Several interventional options were considered:

• Angioplasty has been a successful strategy in lower extremity bypass stenoses. Cutting or scoring balloons typically have had better outcomes than plain balloons due to the ability to allow dilation at lower pressures and to deal with the intimal hyperplastic nature and the “watermelon seed” movement of plain balloons over these smooth stenoses. This approach was not chosen due to the large diameter mismatch of the artery to the vein and the lesion being primarily of the artery.
• Stents placed across the thoracic outlet typically are at risk for stent fracture if the thoracic outlet has not been surgically decompressed with rib removal. The CT was done with the patient’s arms above the head and confirmed adequate surgical decompression of the space, making stenting an option.
• Self-expandable nitinol stents have yielded good outcomes in treating subclavian artery occlusive disease. The large vein diameter would have required a very large self-expanding stent. We felt the risk of distal migration would make a stent of this type a less-than-ideal choice.
• Self-expandable drug-eluting stents have had good patency in the femoral arterial segment. The shortest commercially available stent is 40 mm long, which would have been too large for this short lesion. The largest diameter is 8 mm and would have had the same risk of distal migration as a plain nitinol stent.
• Balloon-expandable drug-eluting stents have had excellent results in the coronary circulation and come in short lengths but are not available in large enough diameters for this vessel.
• Drug-eluting peripheral balloons were also considered, but the balloons are long and would require treatment of a long segment of normal vessel, and there are no data on the efficacy of this approach.
• We decided to use a peripheral balloon-expandable stent to allow flaring of the distal portion to accommodate the diameter mismatch from the subclavian artery to the vein bypass. We felt this had the lowest chance of migration.

Treatment, outcome and follow-up

A 6-mm-diameter, 17-mm-long stainless steel stent was used and was flared to 10 mm distally. The completion angiogram was normal (Figure 3).

Figure 3. Angiogram taken after stenting and flaring of the distal stent. Note the absence of residual stenosis.

The patient was discharged the same day on dual antiplatelet therapy and returned for office follow-up six weeks later with normalization of the duplex velocities, normal plethysmography and equal brachial pressures. We expect to continue to follow her for this problem for many years to come.

Dr. Lyden is Chair of Cleveland Clinic’s Department of Vascular Surgery.