Percutaneous Removal of Large, Fresh Thrombus in Central Venous Disease with the AngioVac System

Disclosures: Dr. Gurley reports no conflicts of interest regarding the content herein.

Dr. John Gurley can be contacted at j.gurley@uky.edu.

Can you tell us about your facility and practice?

I am at the University of Kentucky, a large academic medical center. We serve a network that performs about 2500 procedures annually, and the University of Kentucky cath lab is the referral center for many non-routine cardiovascular problems. We have a very active valve and structural heart program.

We also see a great deal of complex central venous disease, including superior vena cava (SVC) and inferior vena cava (IVC) occlusions, frequently associated with large clots that extend into the right atrium of the heart. We first began using the AngioDynamics AngioVac Cannula and Extracorporeal Circuit (AngioVac System) about a year ago, in order to manage large thrombus burdens that affect the IVC and SVC. In our practice, the role of the AngioVac is to remove obstructions in these large central veins.

How will patients present?

The typical presentation of acute venous obstruction in the lower body includes sudden pain and swelling of the legs. The symptoms can be quite extreme. These patients usually have extensive thrombosis of the pelvic veins and the inferior vena cava (IVC) that is precipitated by an underlying mechanical venous obstruction and a pro-thrombotic medical condition. In the upper body, patients present with sudden swelling and purplish discoloring in the head, arms, and upper chest. Here we see acute thrombosis of the superior vena cava (SVC) associated with an underlying stenosis or central venous catheter. 

How are these patients treated?

Our approach to treatment has four steps: 1) diagnose the problem quickly; 2) remove the acute thrombus; 3) correct the underlying mechanical obstruction; 4) identify predisposing medical conditions associated with hypercoagulability. 

Computed tomography (CT) is the preferred test for diagnosing thrombotic occlusions of the large central veins. This imaging modality defines the extent of thrombus burden as well as the source of underlying mechanical obstruction. The AngioVac system helps us remove the large, acute thrombus while avoiding embolization. Mechanical obstructions are managed with interventional techniques. Here we might remove a chronic IVC filter that has thrombosed, place a large self-expanding iliac vein stent for May-Thurner syndrome, remove a clotted central venous catheter, or stent a SVC stricture. Finally, it is important to screen for medical conditions that cause hypercoagulability. The medical condition can be something as simple as an orthopedic injury that causes the patient to be immobile for a period of time, although there are more ominous conditions. 

How does the AngioVac System work?

The concept is fairly simple. It involves aspirating the thrombus through a large-bore cannula connected to a high-flow pump. The AngioVac cannula has a shaped tip that opens like a tulip, creating a flow vortex that facilitates aspiration of thrombotic material into the cannula. Blood and thrombus flow through the cannula into a filter. The thrombus is trapped in the filter while blood is returned to the body through a second venous cannula. The circuit that we use is a modification of a cardiopulmonary pump, such as the one that is used for extracorporeal membrane oxygenation (ECMO). The AngioVac Cannula and Circuit are used with a standard centrifugal pump, bubble trap, and reinfusion cannula. The use of an extracorporeal circuit and cannula are unique to the AngioVac system. The system comes with a set of tubing and clamps to make the set up easy. 

The AngioVac works well for soft, fresh thrombus in large venous structures that include the SVC, IVC, the right atrium, and also the iliofemoral venous system. It solves a problem that previously was unsolved or poorly solved. Up until we began using the AngioVac, we did not have the ability to remove large amounts of thrombus from the right atrium of the heart, the IVC, or the SVC, without high-risk open surgery.

Were patients usually medically treated?

We did often treat patients with anticoagulation and hoped for the best. We have learned that patients with acute iliofemoral deep vein thrombosis and massive swelling of the legs do very poorly in the long term. These are patients who end up suffering from post-thrombotic syndromes, with chronic edema, swelling and venous ulceration of the lower extremities. 

I think the venous system has been neglected for a long time, mostly because the medical community simply has not known what to do with patients who have thrombotic or occlusive problems involving the central venous system. When we didn’t know what to do, we tended to not do anything. We now know that central venous occlusions are actually quite common. Unfortunately, many patients with these large central vein occlusions who are managed conservatively go on to a lifetime of disability. Now that we have a set of tools to deal with this problem, our practice has changed. We believe that early intervention can prevent post-thrombotic syndromes and preserve patency of the central venous system. We see a great many of patients with complex central vein occlusions, and a good portion of them require dialysis access or other lifesaving therapies that simply cannot proceed without access to the central circulation.

Where do you gain access for the AngioVac procedure?

We insert the cannula percutaneously through the femoral vein or through the internal jugular vein, using a 26 French (F) sheath. The location of the thrombus determines which point of access is preferred. For example, if we have a patient with an acute occlusion of the IVC due to thrombosis of an IVC filter, that patient may have a large burden of thrombus above the filter, and any intervention to reopen the IVC would risk embolization to the lungs. In this case, we would insert the AngioVac cannula through the right internal jugular vein and advance it downward into the IVC. After eliminating the thrombus burden above the filter, we would then leave the cannula in place to catch any thrombus that might dislodge during removal of the filter or stenting of the IVC. 

The AngioVac procedure can be performed by operators with a variety of backgrounds. Interventional radiologists, interventional cardiologists, vascular surgeons, and/or cardiothoracic surgeons have the wire and cannula skills necessary to insert the cannula. Anyone who has experience with central venous access and central venous interventions will find the AngioVac cannula fairly easy to insert. A perfusionist supports the pump circuit that aspirates, filters and reinfuses blood. Any hospital that does cardiac surgery will have a perfusion team that will feel comfortable with the AngioVac procedure. The AngioVac circuit is the simplest circuit that a perfusionist has to deal with, simpler than what is required for mechanical circulatory support. It consists of the AngioVac cannula, some tubing, a filter, a pump, and a re-infusion cannula. The re-infusion cannula is a standard vascular cannula that we would use for one of these perfusion circuits, typically 17F. We take the blood out of a vein, pass it through a filter, and re-infuse it through a vein. 

How do you visualize the thrombus during the AngioVac procedure?

We use echocardiography during right atrial and SVC procedures. Transthoracic, transesophageal and intracardiac imaging methods are all suitable. For iliac and IVC procedures, we use angiography supplemented by intravascular ultrasound. Thrombus removed from the body is visible in the filter cone of the device. 

How long of a procedure is it, typically?

Initially, the set up of the pump and circuit might seem to be challenging, but that is only due to a lack of familiarity. We can perform the AngioVac procedure in 30 minutes to an hour. At our hospital, all of our cases include advanced interventional fellows, who learn how to set up the equipment quickly. If one operator connects the tubing while another inserts the sheath and return cannula, the system can be ready to go in 10 minutes. These cases are not unusually time-consuming. They are quite efficient.

Once the procedure is completed, how long does the patient stay in the hospital?

The hospital course is usually determined by the underlying illness and not the AngioVac procedure. When we remove the cannula, the site is closed with a temporary purse string suture. The patient requires overnight bed rest and then is allowed to be ambulatory, so the AngioVac procedure itself doesn’t really limit the patient.

What have you seen with your patients after the AngioVac procedure?

Typically, patients will improve immediately, with relief of swelling and pain in their affected segments. For example, if the thrombus is in the inferior vena cava and the iliofemoral system, these patients will experience almost immediate reduction in pain, discoloration, and swelling — by immediate, I mean within a matter of hours. We see patients who are immobile because they have so much swelling and pain from a recent occlusion, and we have seen these same patients return to completely normal activity within a week or two.  

You mentioned the AngioVac is for soft, fresh thrombus and patients sometimes present acutely. What is the ideal time to treatment?

This is where it is important to get the word out to our colleagues. I think there has been too much of a therapeutic nihilism in the broader medical community, based on a general belief that you really can’t do much with occlusive thrombus in the large central veins. This is not true. For patients with an acute obstruction of the large central veins, the disability can be very long-term and very severe. When we see patients with acute arterial occlusive disease, what do we do? We act with a sense of urgency. We monitor door-to-balloon time for percutaneous coronary intervention in patients with acute myocardial infarctions. We treat critical limb ischemia as an emergency. But when venous disease is present, patients are too often allowed languish. They may be referred for intervention only after they don’t do well for a week or two. Venous disease is best treated early, when the thrombus is fresh and soft, and by early, I mean two weeks. Clot removal strategies are most effective in the first two weeks. If patients are referred for treatment within two weeks, we can probably remove the thrombus effectively. Sometimes we don’t know how long the disease has been in process, and in those cases, we often will give the patient the benefit of the doubt. But a timeframe of within two weeks is ideal, and the sooner, the better. 

How does the presence of thrombus in the venous system differ from the arterial system?

In the arterial system, occlusive thrombi tend to be very small. The underlying problem is usually atherosclerosis, with a severe stenosis caused by plaque buildup. A small acute thrombus is sufficient to cause complete occlusion. Embolic occlusions may involve a larger thrombus but for the most part, acute arterial occlusion involve atherosclerosis and a very small thrombus. Unlike the arteries, veins do not develop atherosclerotic narrowing. Clots that form will fill the entire lumen of the vein. The iliac veins, for example, are as big as your finger, so the thrombi that form here can have a very large volume. When these thrombi embolize to the lungs, they can obstruct the pulmonary vasculature to a critical level, causing shock. We will often use the AngioVac as a protective strategy to prevent pulmonary embolism when a large thrombus burden is present, placing the cannula between the thrombus and the lungs, so that the thrombus is removed from the body rather than being allowed to migrate to the lungs. 

What do you see happening in the future?

There are two things that need to happen. First, we need to educate our colleagues in the emergency department and in the intensive care unit. We need to spread the word that venous thromboembolic disease is common and it causes a great amount of acute risk as well as long-term disability. Venous thromboembolic disease is actually the third leading cause of hospital-related death. It is third only behind heart disease and cancer. And of those three diseases, venous thromboembolic disease is possibly the most preventable. Patients with proximal lower extremity deep vein thrombosis may present acutely with swelling of the legs, and we have to educate our frontline physicians that this is dangerous. These patients have a 50% risk of pulmonary embolism if they are treated conservatively, and perhaps a 40% risk of post thrombotic syndrome that can lead to long-term disability. Frontline physicians in the ED and the intensive care units must approach acute venous occlusions with the same urgency as acute arterial occlusions. Venous thromboembolic disease is common, dangerous, and very treatable if managed early. 

Second, we must continue to develop the systems of care to deliver effective treatment strategies that prevent a long-term disability. Communities must develop local expertise so that frontline clinicians can easily access newer tools such as AngioVac, which is an exciting advance in our campaign against central venous disease. 

I believe that AngioVac will be increasingly added to the practice of interventional radiologists, interventional cardiologists, and vascular surgeons who treat central venous diseases. While this new tool will allow us to treat central venous diseases that previously couldn’t be treated, the role of AngioVac will need to be better defined as we gain experience. We are not going to use AngioVac for every case of iliofemoral deep vein thrombosis. We are not going to use AngioVac for every patient who has a catheter-associated thrombus in the right atrium. The AngioVac system must be utilized selectively and responsibly. 

Currently, AngioVac is the only non-operative method for physically removing large amounts of obstructing thrombus from the large central veins and the right atrium. Sometimes it is the only option. Alternatives such as thrombolysis are often contraindicated because of recent surgery or bleeding disorders. And the risks of open surgery for central venous thrombosis are usually prohibitive. AngioVac appears to have a secure role in our protocols for dealing with complex central vein disease. 

What happens when you come upon a thrombus that can’t be treated with the AngioVac?

These cases usually involve thrombus that is old, organized, and firmly adherent to the vessel wall. These thrombi are unlikely to embolize, so they can be managed with a strategy of anticoagulation and vascular stents. A period of anticoagulation allows the thrombi to organize and reabsorb as much as possible. Residual stenosis caused by incomplete reabsorption, vessel wall contracture, or external compression can then be treated with balloon dilatation and stenting. 

Thrombus removal is not always a standalone strategy. As we have discussed, venous thrombosis typically involves two predisposing factors: mechanical obstruction and a hypercoagulable state. Removing the acute thrombus is only part of the solution. A good example of this is acute IVC occlusion in a patient with an IVC filter. An IVC filter that becomes narrowed by organized thrombus and fibrotic contracture can set the stage for thrombosis. In those cases, we remove the acute thrombus, and then address the remaining stricture using interventional techniques. Usually, we remove the filter. Filters that cannot be removed are stented open. Either way, our objective is to relieve the predisposing obstruction. 

Another example is IVC thrombosis associated with trauma. One of our early AngioVac cases involved a young woman who had been severely injured in a car crash. She underwent lifesaving surgery to stop bleeding from the liver, but the sutures narrowed her IVC near the diaphragm. This led to massive thrombosis of the IVC from the groin to the diaphragm. Thrombolysis and repeat surgery were out of the question. We utilized AngioVac to remove the thrombus, followed by stents to gradually reopen the IVC. The excellent outcome in this case could not have been achieved without the AngioVac. 

Any final thoughts?

The University of Kentucky has become a significant referral center for managing complex central vein disease. The techniques for dealing with this problem are evolving, and new tools like AngioVac are helping us become more capable every year. We now feel that we can offer a solution for even the most difficult central venous obstructions. As a cardiologist, I am happy to treat coronary disease and I enjoy structural heart work, but I have learned that successfully managing complex central vein disease can be equally rewarding. Central venous disease can cause as much or more disability than arterial disease, and it is remarkably gratifying to see how these patients recover. We can and we must help eliminate the long-term disabilities associated with central venous disease.