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Prevalence

Venous thoracic outlet syndrome (Paget-Schroetter syndrome or effort thrombosis) comprises only 5 % of all cases of thoracic outlet syndrome. It is estimated that between one [1] and two [2] patients per 100,000 of population per year experience this syndrome. The natural history of this disorder is progression to chronic thrombosis with significant disability [3]. Anticoagulation improves outcomes when compared to the natural history of this disorder, but many patients still have chronic thrombus and experience residual symptoms [4, 5].

A variety of interventions have been developed and implemented with success, largely ­preventing late thrombosis and alleviating chronic disability. However, some patients do not seek treatment until after a significant time interval has elapsed. Some patients present when they first have symptoms but the diagnosis is not made in a timely fashion. Other patients do undergo timely treatment, but the treatment fails to resolve the thrombus or the clot resolves but then recurs later. These patients comprise a group of patients with venous thoracic outlet most at risk currently for long-term disability, so devoting separate consideration to their treatment is important.

Definition

There is no standard length of time that determines an axillo-subclavian vein occlusion as acute verses chronic. Many authors support “early” treatment, which means hospitalization and intervention at first presentation [6–8]. “Chronic” thrombosis, by contrast, was defined in one series as patients presenting for treatment at a mean of 22 weeks after diagnosis [9]. Somewhere between first presentation and 22 weeks later is an arbitrary line defining these two entities. Illig and Doyle define the distinction between acute and chronic thrombus at 2 weeks after initial symptoms due to the likelihood of success of attempted thrombolysis [1]. In addition, patients with recurrent venous occlusions can present as a result of failure of a variety of interventions including thoracic outlet decompressive surgery, venous thrombolysis with or without stenting, anticoagulation, or a combination of these interventions [10–14].

Acute Thrombus Management

In the ideal setting a patient will present very soon (hours to days) following thrombosis. Assuming the proper diagnosis has been made, the standard of care has evolved to be preliminary catheter-directed thrombolysis followed by decompression of the venous thoracic outlet after the clot has been lysed. This pathway has been determined without the benefit of any type of randomized controlled clinical trial (see Chap. 83). Differences of opinion exist as to timing of decompression and management of residual defects, but this general algorithm is the most commonly used. Thoracic outlet decompression in this situation is designed to keep an open vein open – i.e. to prevent recurrent thrombosis in a vein where patency has been restored. Many patients, for the reasons cited above, however, will have continued occlusion of the subclavian vein despite all efforts at recanalization.

Chronic Thrombus Management

Most authors agree that the primary factor in venous thoracic outlet syndrome is mechanical compression of the subclavian vein at the anterior aspect of the thoracic outlet where the vein passes posterior to the subclavius muscle and tendon and anterior to the anterior scalene muscle. This premise is true for both acute and chronic presentations of this disease. Therefore, it is important to focus on correcting this problem first, and not correcting the actual venous occlusion primarily. If the venous lesion can be traversed with a wire (but not otherwise corrected), it is tempting to try to “force” the vein open with a stent. This should be avoided because stenting prior to surgical thoracic outlet decompression has been found to be related to higher rates of venous occlusion in multiple series [10, 15]. The problem is extrinsic compression by relatively fixed bony structures, coupled with a very strong lever arm with movement of the arm. No stent can withstand these forces, and stent fragmentation, common in this situation, makes a bad situation even worse. Several studies suggest that even successful preoperative thrombolysis may not improve long-term subclavian venous patency and relief of symptoms in patients with “subacute” and “chronic” occlusions [14, 16].

Hopkins Protocol

A protocol has been developed at Johns Hopkins Hospital by Freischlag and associates that demonstrates this understanding of venous thoracic outlet syndrome pathophysiology. Patients that present late with subclavian vein thrombosis caused by thoracic outlet syndrome are first given injectable anticoagulation followed by oral warfarin. They are evaluated as outpatients by history, physical exam, and duplex ultrasound. Trans-axillary first rib resection is performed within weeks of evaluation. Two weeks after surgery, diagnostic venogram is performed which is accompanied by venoplasty, if indicated and technically feasible. If the vein remains occluded, or if it is patent and a percutaneous procedure is performed, oral anticoagulation is continued for 3 months. If the vein is patent and requires no intervention during the venogram, anticoagulation is discontinued. Physical therapy is begun 2 weeks after surgery, and is continued for 6–8 weeks. Recent data suggest that chronic venous occlusions that are resistant to postoperative percutaneous intervention may actually recanalize months to years following surgical decompression [9]. Follow-up imaging of the subclavian veins is obtained with venous duplex ultrasound.

These results support the hypothesis that decompression of the thoracic outlet is the critical step in treating chronic venous thoracic outlet syndrome, but does not provide specific clues about why this is true from a pathophysiologic standpoint. Potential theories include the interruption of chronic trauma to the subclavian vein, allowing it to recanalize. Another potential benefit of thoracic outlet decompression is to improve flow in collateral veins, which improves the venous hemodynamics of the upper extremity. Another factor could be the effect of anticoagulation. While not likely to change outcomes in isolation, anticoagulation in combination with surgical decompression may tip native anti-thrombotic processes enough to recanalize the vein in the long-term.

Imaging Techniques

Venography is the gold standard to demonstrate patency or occlusion of the subclavian vein. Duplex ultrasonography may not adequately differentiate between a recanalized subclavian vein and a large collateral vein adjacent to an occluded subclavian vein. However, in patients who are asymptomatic weeks to months after thoracic outlet decompression and venography, justifying an invasive procedure to make this differentiation is unfounded because it will not alter future treatment. In addition, serial duplex ultrasonography performed by technologists experienced with thoracic outlet syndrome diminishes the likelihood of inaccurate interpretation due to the ability to compare serial ultrasound images and venography images to prevent misidentification of a collateral vein.

Other Scenarios

Patients with recurrent thrombosis may have had subtotal thoracic outlet decompression, and thus require repeat surgery [17]. This can be performed safely and requires exhaustive attention to the adequacy of first rib resection. Patients who continue to be symptomatic and have continued subclavian vein occlusion following complete thoracic outlet decompression and postoperative venoplastymay be candidates for venous reconstruction. This can be performed with saphenous vein bypass or jugular venous turndown. These procedures typically require incisions above and below the clavicle and may even require partial claviculectomy. There is little data regarding these procedures mostly because the number of patients requiring this eventual intervention is quite low (see Chap. 65).

Outcomes

Many patients with chronic occlusion of the subclavian vein return to their baseline functional status, without major symptoms. The patency rates for the involved subclavian vein are slightly worse than the rate of patients who are symptom free in most series [4, 17, 18], implying that vein patency should always be the ultimate goal of treatment. Extensive collateral venous networks frequently develop around a subclavian vein thrombosis (see Fig. 56.1). These collaterals protect the patient from symptoms of upper extremity venous hypertension even if the subclavian vein remains occluded. When considering further invasive treatment for an occluded subclavian vein, the presence of venous collaterals and the potential for damaging them with further interventions needs to be carefully considered.

Fig. 56.1
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Occluded right subclavian vein with extensive collateral veins

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