The etiology of subclavian vein obstruction may be primary, when there is no known reason for the obstruction, or secondary, in which there is a known reason for the obstruction to occur. In both primary and secondary subclavian venous obstructions, extrinsic pressure or intrinsic trauma can produce either a thrombotic or non-thrombotic occlusion secondary to stenosis of the subclavian vein.

A thrombus must be treated separately prior to further intervention to relieve the cause of the obstruction. The majority of patients have secondary subclavian vein obstruction from intimal damage due to the insertion of catheters or pacemaker wires.

Other known secondary causes are thrombosis from underlying coagulopathies, extrinsic pressure on the subclavian vein due to cancer, and from irradiation (which can cause intimal damage from ongoing vasculitis or extrinsic compression from scarring and fibrosis).

Primary subclavian vein obstruction is also known as effort thrombosis or Paget-Schrötter syndrome, which was first described by Paget in 1875 and von Schrötter in 1884. The underlying cause of primary subclavian vein occlusion is often due to a congenitally narrowed costoclavicular space (also termed the thoracic outlet) for passage of the subclavian vein as it joins the innominate vein. In the costoclavicular space, the costoclavicular ligament and subclavius muscle surround the subclavian vein as it passes between the first rib and the clavicle to enter the mediastinum.

The possible causes for primary obstruction of the subclavian vein are (1) enlargement of either the ligament or the muscle, (2) a narrow angle between the clavicle and the first rib, or (3) the position of the subclavian vein that is too medial compared to normal. In any of these possibilities, the vein lies too close to the costoclavicular ligament and is subject to trauma, particularly from strenuous arm motion, hence the rise of the term “effort thrombosis” to describe this condition. The repetitive trauma leads to intimal injury, thickening, or web formation, and stenosis can result. Thrombosis is the final event, and it may be acute or chronic or never occur.

Other more rare causes of subclavian vein obstruction are (1) an anterior-lying phrenic nerve, (2) congenital bands and ligaments, (3) the pectoralis minor tendon, and (4) thickened venous valves, either congenitally hypertrophied or in response to extrinsic pressure and trauma [13–39].

Clinically, two-thirds of reported cases of subclavian vein thrombosis occur on the right side. This may be due to the acute angle between the right subclavian and innominate veins when compared to the left, which is almost straight, resulting in hemodynamically more turbulent flow on the right. Another proposed explanation is that more people are right-hand dominant and therefore the right arm is more likely to be used for strenuous activities. Men are more likely than women to develop subclavian vein obstruction, and the exact reason for this is still unknown. Paget-Schrötter syndrome is most often a disease of young, active, healthy patients.

Symptoms are the same for both thrombotic and non-thrombotic occlusions, and these include sudden swelling of the hand and arm, a pressure sensation of the arm, and pain, all of which are aggravated by physical activity. Some patients may describe the arm as having a “bursting” feeling. The majority of patients with non-thrombotic occlusions will have had a gradual onset of symptoms, while patients with thrombotic occlusions may have had an acute or gradual onset. In retrospect, many people with an acute thrombotic presentation often had earlier milder symptoms of pain and swelling but did not initially seek medical attention until more severe symptoms suddenly appeared. Patients who present after the initial venous thrombosis has resolved may only demonstrate symptoms with physical activity.

On physical exam, in addition to the swelling of the hand and arm, there may be cyanosis or rubor and distended veins around the shoulder or lateral chest, indicating the development of collateral circulation (“first rib collaterals”). In patients with effort thrombosis, pallor, sweating, and fatigue may also accompany their hand and arm symptoms. Workup often starts with noninvasive duplex scanning, but occasionally it may not be possible to visualize the subclavian vein due to the clavicle. A positive duplex scan is followed by diagnostic venogram, which is the gold standard for diagnosis. If there is partial obstruction, dynamic venography is essential, as occlusions may not be seen unless the arm is elevated to 90–180°, hyperabducted, or even adducted [39]. See Chap.​ 9 for a further discussion of workup and diagnostic imaging.

Secondary subclavian venous thrombosis is usually treated conservatively with anticoagulation: heparin initially followed by warfarin for 3–6 months. The offending indwelling catheters or wires should be removed. In dialysis patients, where their functioning arteriovenous fistula (AVF) is in the offending arm, removal of the AVF will often relieve the symptoms. However, if retention of the AVF is necessary, transluminal angioplasty (with stent placement if absolutely required) or surgical bypass via axillary, brachial-internal jugular bypass, or central vein bypass may be performed to decompress the arm.

Primary subclavian vein obstruction is usually symptomatic when presented and must be treated aggressively in the following order: (1) remove the acute thrombus if present and reestablish axillosubclavian venous patency, (2) relieve the extrinsic pressure by decompression of the costoclavicular space, and (3) eliminate the intrinsic defect. The acute thrombus is treated by catheter-directed thrombolysis with tissue plasminogen activator (tPA), urokinase (UK), or potentially, in some cases, by pharmacomechanical thrombolysis, followed by systemic anticoagulation to maintain venous patency with heparin followed by warfarin. Lytic management of acute venous thoracic outlet syndrome (TOS) is demonstrated in Fig. 15.5. Although thrombolysis is most successful in thrombus less than a few days old, it can dissolve clot several weeks to (in some cases) several months old. Indications for surgical thrombectomy are failure of lysis to reestablish venous outflow, patients who have contraindications to fibrinolytic therapy, or technical inability to deliver the agent directly into the thrombus of patients who experience persistence of severe symptoms (Fig. 15.6).

Once venous patency is established, the underlying cause of the occlusion should be repaired, and in most cases, this is due to the extrinsic compression of the subclavian vein at the costoclavicular ligament. The relief of extrinsic compression is by first rib resection, either by a transaxillary, supraclavicular, or infraclavicular approach. The supra- or infraclavicular approach may be optimal if concomitant exploration or reconstruction of the subclavian vein is anticipated. In any case, it is necessary that the anterior portion of the first rib be removed along with sufficient costal cartilage to totally free the subclavian vein.

The timing of resection of the first rib remains controversial. Traditional protocols advocated systemic anticoagulation for 3 months prior to surgical intervention, due to potential coagulation issues in the patient following lysis. Most surgeons believe there is no difference in rethrombosis of the vein despite a 3-month delay in surgery for extrinsic compression. However, currently in many centers, first rib resection is performed either during the same hospitalization or at the time of thrombectomy [39]. Rethrombosis of the vein following lysis or decompression should be treated with repeat lysis. If the subclavian vein cannot ultimately be opened by lysis or other techniques, some would omit first rib resection since there is no reason to decompress an already occluded vein, perhaps with the exception of an open proximal subclavian vein from a cephalic vein collateral. However, some argue that there is a potential role for first rib resection or other TOS surgery even in those with an occluded subclavian vein [28].