Most authorities separate the treatment of venous TOS into two stages: immediate initial treatment and subsequent definitive treatment. Immediate treatment consists of prompt dissolution of the blood clot in the subclavian vein. Definitive treatment prevents recurrence of blood clot.
As soon as a physician diagnoses venous TOS, he or she will begin treatment in nearly all patients with thrombolytic agents. The doctor inserts a catheter in a vein, places the tip of the catheter at the blood clot, and delivers the thrombolytic drugs to the clot. Thrombolytic agents directly dissolve the blood clot. Doctors call this process catheter-directed thrombolysis. In contrast to catheter-directed thrombolysis, anticoagulants prevent further blood clot formation, allowing the body to dissolve the blood clot. However, the body dissolves blood clot much more slowly than does catheter-directed thrombolysis.
Catheter-directed thrombolysis can cause serious side effects. One major side effect is unexpected bleeding elsewhere in the body, such as the brain. For this reason, patients who undergo this treatment are admitted to an acute care facility for close observation. Nurses and doctors observe these patients closely for one to several days, until the blood clot has resolved.
A new method is safer and faster. Doctors perform pharmacomechanical thrombectomy through a specialized catheter within the vein. This catheter is specially designed to mechanically break up the clot. At the same time, it delivers a much smaller amount of thrombolytic agent. Pharmacomechanical thrombectomy can dissolve clot within hours, eliminating the need for observation of the patient in an acute care facility.
Initial treatment is considered complete when the blood clot has completely resolved. A physician will perform serial direct venograms to assess the progress of catheter-directed thrombolysis, and confirm successful initial treatment.
Following initial treatment, the doctor selects and begins definitive treatment. Most authorities have traditionally divided definitive treatment of venous TOS into conservative and surgical approaches.
Conservative treatment of venous TOS consists of four components following initial treatment:
Intermittent arm elevation
Restriction of activities that cause symptoms
Unfortunately, conservative treatment often results in poor outcomes. These outcomes include restricted activity, chronic venous congestion, and recurrence of blood clot. Blood clot recurs in greater than 50% of patients treated conservatively. Additionally, there is no convincing evidence that proves the optimum duration of anticoagulation treatment. Furthermore, these patients may need anticoagulation for life. Anticoagulation treatment increases the risk of bleeding throughout the body. For these reasons, most authorities consider conservative treatment of venous TOS less optimal than surgical treatment.
Surgical treatment of venous TOS consists of four stages:
Immediate treatment of blood clot (described above)
Definitive treatment of extrinsic vein compression
Definitive treatment of intrinsic vein damage
Follow-up venography to assess patency of the vein and recurrence of blood clot
After initial treatment to remove blood clot, doctors initiate definitive and timely treatment of the underlying causes of blood clot. Specifically, the physician surgically releases the extrinsic structures compressing the vein. Shortly thereafter, the physician will repair the intrinsic vein damage. Equally important, the physician should complete definitive treatment in a timely manner to achieve the best outcome.
The surgeon releases all of the structures that he or she finds compressing the subclavian vein. In reality, the surgeon often uses a small incision and surgical window. The surgeon may have difficulty determining which structures compress the vein when the patient is conscious and upright. For this reason, many surgeons err on the side of caution and remove any and all structures which could potentially compress the vein. Notwithstanding the value of surgical experience, preoperative MRI would accurately demonstrate the compressing structures, and provide an accurate surgical roadmap. At the present time, MRI is not widely used for this purpose.
Intrinsic Vein Repair
Following or accompanying extrinsic decompression, the surgeon will almost always repair the damaged vein. Although the surgeon has removed the tissues around the vein, the prior compression may have caused damage to the vein. This damage increases the risk of recurrent blood clot.
At some centers, the surgeon repairs the damaged subclavian vein immediately following decompression, as a part of the total surgical procedure. The surgeon can perform intraoperative venogram immediately after decompression to assess residual vein damage. The surgeon selects surgical repair of the vein if the venogram is abnormal. It is important to note that there are a number of different surgical approaches to the thoracic outlet. However, only a few of these offer adequate access to repair the damaged vein. If the surgeon repairs the vein through an inadequate window, there is a higher risk of recurrent venous scarring. As a result, there would be a higher risk of recurrent blood clot.
In many centers, the surgeon performs decompression surgery without direct vein repair. In this situation, routine venogram is performed two weeks after surgery. Venogram usually demonstrates one of the following: a fully patent vein, a residual venous stenosis (scar), or occlusive blood clot.
Venogram findings determine the next treatment step.
If the vein is patent, no further treatment is performed.
If the venogram demonstrates venous stenosis, venoplasty or balloon angioplasty is performed. A physician performs venoplasty by inserting a specialized catheter with a ballon at its tip and performing a venogram. The physician uses the venogram to identify the abnormal section of vein, then advances the catheter to this location. The catheter balloon is inflated across the scar, stretching the vein and reducing or eliminating the scar.
If the vein is occluded by recurrent blood clot, the patient is treated for several months with anticoagulation drugs.
Some centers have utilized pre-operative venoplasty, followed by decompression surgery. This approach has not yielded better outcomes, likely because the extrinsic compressing structures prohibit adequate vein expansion during venoplasty.
A stent is an expandable metal cage which provides an alternative method to perform intrinsic vein repair. A physician uses a specialized catheter with a collapsed stent surrounding a balloon. The physician performs a venogram to find the damaged segment of the subclavian vein. Then the physician advances the catheter so that the collapsed stent is located within the damaged vein segment. The physician inflates the balloon, which expands the venous scar and expands the stent. The expanded stent prevents new scar or narrowing. At present, physicians do not commonly use stents, due to a high rate of stent failure and recurrence of clot.
Timing of Surgical Treatment
Timing of treatment is critical in determining outcome. If definitive treatment is performed within 2 weeks of symptom onset, treatment success is close to 100%. Many authorities believe that definitive treatment may be equally successful up to 6 weeks after symptom onset. However, other patients may not do as well. Symptom duration longer than 6 weeks, chronic venous occlusion, or long-segment venous scar are associated with a lower success rate. These patients may require lifelong anticoagulation treatment.
In general, if an early diagnosis is made and definitive treatment is performed promptly, excellent surgical outcomes are achievable. Surgical decompression and direct vein repair, or surgical decompression with follow-up venogram and venoplasty both provide excellent results.