Thrombus Management

Expanding Your Practice With a Percutaneous Vacuum-Assisted Thrombectomy System: The AngioVac Cannula and Circuit

Cath Lab Digest talks with Eric J. Lehr, MD, PhD, FRCSC, Swedish Heart and Vascular Institute, Seattle, Washington.

Cath Lab Digest talks with Eric J. Lehr, MD, PhD, FRCSC, Swedish Heart and Vascular Institute, Seattle, Washington.

Disclosure: Dr. Lehr reports having received travel assistance to attend AngioVac User Meetings. He is also a member of the Medical Advisory Board for Edwards Lifesciences.

Dr. Eric Lehr can be contacted at eric.lehr@swedish.org.

A newly created response team at Swedish Medical Center is drawing a growing number of thrombus-related referrals from both in-house and regional physicians. Founding team member and cardiac surgeon Dr. Eric Lehr shares his personal experience over the past 5 years with the percutaneous AngioVac vacuum-assisted thrombectomy device (AngioDynamics) and describes its impact.

How does the AngioVac work?

The AngioVac is essentially a mini cardiopulmonary bypass circuit that replaces the oxygenator in a regular cardiopulmonary bypass circuit with a filter. It comes as a set with tubing as well as a special aspiration cannula. The AngioVac cannula is cleared by the FDA and indicated for use as a venous drainage cannula for the removal of fresh, soft thrombi or emboli during extracorporeal bypass for up to six hours. The device may be used in target vessels for thrombus/embolus extraction that include, but are not limited to, the iliofemoral vein, inferior vena cava (IVC), superior vena cava (SVC) and right atrium (RA), which opens up its use for a variety of pathologies. The aspiration device is a long 22 French cannula and at the end is a balloon with 4 leaflets attached. When the balloon is inflated, the leaflets are deployed and extend to create a funnel, which generates a vortex to facilitate better entrapment of the undesirable material. The latest generation of the AngioVac device is available in two models: one is straight, and the other has a 20-degree bend at the tip, which aids in steering. The new model also has radiographic markers on each of the petal tips, to allow for better visualization. Important changes have been made to the circuit as well. A Y-adapter and working side port allows the use of a Tuohy connector so that the system can be run over a wire. A working port allows for other devices to be used in conjunction with the device such as a snare or a cleaner wire, or a number of other devices that may be complementary. A bag has been added to the filter that allows us to temporarily turn off the circuit and wash off the filter without having much blood loss. We can then assess to see what has been collected in the filter, helping to determine how effective the procedure has been in addition to relying on fluoroscopic images. 

In what type of room do you typically use the AngioVac?

We are fortunate to have a very advanced hybrid room and my preference is to use it there. The hybrid room affords excellent imaging and the capability to perform any adjunctive operative procedures as required. If we are doing a pulmonary embolectomy case with the AngioVac, for example, we would have the ability to convert to an open pulmonary embolectomy if necessary. A hybrid room provides the best versatility, but AngioVac can also be used in cath labs or interventional radiology suites.

How often are you crossing to an open procedure when you start with an AngioVac? 

I have done that once so far. The patient had a submassive pulmonary embolism and had previously undergone cardiac surgery. Intraoperative transesophageal echocardiography noted thrombus in transit across a patent foramen ovale (PFO). We were uncomfortable extracting that thrombus with AngioVac so we performed a redo-sternotomy and open pulmonary embolectomy with extraction of the thrombus in transit and closure of the PFO.

What first prompted your interest in the AngioVac?

My use of AngioVac was natural progression from my use of peripheral cannulation for robotic and minimally invasive cardiac surgical procedures. Simultaneously, my interest in chronic pulmonary thromboendarterectomy led to the development of my interest in treating acute pulmonary embolism. These skill sets dovetailed together with AngioVac. As I started using the device, I saw more opportunities to treat patients with endocarditis and venous embolism, as these patient groups have been underdiagnosed and undertreated.  

Can you describe the types of cases where you are using the AngioVac?

There are three main pathologies where I find AngioVac particularly attractive: tricuspid valve endocarditis, inferior vena cava (IVC) on iliac vein thrombosis, and pulmonary embolism. Many tricuspid endocarditis patients are intravenous (IV) drug users who can be very difficult to manage post operatively in terms of analgesia and compliance with sternal precautions. Traditional surgical treatment of tricuspid valve endocarditis involves one of two options. The first option involves surgical replacement of the tricuspid valve, which is fraught with difficulties. We don’t have a great valve replacement for young patients in the tricuspid position. A mechanical valve requires a very high dose of anticoagulation in IV drug users, who tend to be medically non-compliant.  Mechanical valves also complicate the implantation of permanent right ventricular pacemaker leads if required. A biological valve has a short durability in younger patients and sets the patient up for multiple redo procedures. Potentially the valve is repairable, and in those circumstances, that would be the preferred result, but repair of the valve still is most frequently performed via a sternotomy, although some surgeons would approach the tricuspid valve minimally invasively. Regardless, post-operative pain management is always a challenge in these patients. An accepted repair technique if the valve is relatively competent is a vegetectomy, meaning we shave off the vegetation from the valve, and leaving the patient’s own valve. I consider use of the AngioVac to be a percutaneous vegetectomy. It probably leaves just a little base of vegetation that can be handled with antibiotics. An AngioVac procedure does not preclude going back to do surgery at a later date if the patient develops worse tricuspid insufficiency or if the patient fails treatment and has recurrent endocarditis. We can still go back and do a traditional operation. While additional data is required, AngioVac seems to be a great first attempt in the management of these complex patients. I personally know of only one other user who is using it for tricuspid valve endocarditis cases. 

AngioVac can also be used in conjunction with electrophysiologists when performing laser lead extractions of infected pacemaker leads with vegetations. The concern is that the vegetation attached to infected pacemaker leads will embolize to the lungs. We also do this procedure in the hybrid room. The electrophysiologist does the laser lead extraction, and in conjunction, I will bring in the AngioVac. Once the laser is down into the heart and we think that the lead is about ready to go, then we turn on the AngioVac and aspirate the vegetation. There are a few other users that are using the device in conjunction with electrophysiologists in this manner. 

I consider the AngioVac to be a significant advancement in the treatment of endocarditis, particularly in IV drug users, although further data will be required to conclusively prove its effectiveness in this group of patients.

Can you tell us about the use of AngioVac for IVC thrombosis?

Patients can have either acute or chronic thrombosis of the inferior vena cava, often in conjunction with occluded iliac veins and femoral veins. AngioVac is excellent at extracting acute, and in some cases, chronic, thrombus. These patients suffer from leg swelling and pain, and can be quite symptomatic, but are seldom referred for treatment because effective treatment strategies are not widely known. The benefit of AngioVac is that it is a much larger device (22 French cannula), has much better suction, and does a very good job of efficiently debulking the thrombus occluding the IVC.

For chronic cases, it is often beneficial to use adjunctive techniques. First we go in and aspirate the acute thrombus, and then, using a cleaner wire or other device, clean up the chronic component. Adjunctive devices can be placed either through the popliteal vein or the femoral vein, leaving the AngioVac higher up in the IVC to capture all of the debris being dislodged by the adjunctive device.

You also mentioned use of the AngioVac for pulmonary embolism.

Pulmonary embolisms, submassive or massive, often require more aggressive therapy than just heparin alone, and can potentially be extracted with AngioVac. As with most procedures, patient selection is important to ensure a successful result. The ideal case for AngioVac is a simple saddle pulmonary embolism; however, the new generation of the AngioVac device is probably more effective at reaching the branch pulmonary arteries. We can place a stiff wire into the branch pulmonary arteries and traverse over the wire through the right atrium and ventricle, across the pulmonary valve, and then into each branch of the pulmonary arteries. Other options for treating pulmonary embolisms are either thrombolysis, or an open pulmonary embolectomy. Pulmonary embolectomy is very effective at extracting acute and chronic embolisms, but requires cracking the chest open and cardiopulmonary bypass, increasing the length of stay. Other devices are either smaller aspiration cannulas or thrombolysis, either systemic or catheter-directed, which provides a much slower resolution of the thrombus and may not extract all of the thrombus, because of their size. The AngioVac allows us to quickly debulk the thrombus, and most importantly, because it is percutaneous, we are comfortable debulking a majority of the large clot. Because AngioVac is performed percutaneously, if there is still some remaining clot in the pulmonary arteries, it is still possible to do catheter-directed thrombolysis. 

AngioVac would be considered a step up from catheter-directed thrombolysis?

I wouldn’t say that AngioVac is a step up from catheter-direct thrombolysis. Each of these treatment modalities is a tool that is well suited for certain patient populations. In many cases, they are complementary therapies that can be used together to reach a successful outcome.

Does cardiology use the AngioVac differently from interventional radiologists or vascular surgeons?

The AngioVac is primarily used by cardiac surgeons, cardiologists, and interventional radiologists. It is not the specialty that is important so much as having the skills and understanding of how to use large percutaneous devices. Generally speaking, someone with structural heart experience or experience doing thoracic endovascular aortic repair (TEVAR) would certainly have the skill set to do an AngioVac procedure. There is the additional step in terms of the use of a very large circuit, so some understanding of bypass circuits would be helpful, but this is certainly something that can be learned. It is also important to have a perfusionist running the pump and supervising the set up of the pump. With appropriate training, a practitioner with the appropriate skills, including catheter skills, a perfusionist, and scrub techs or nurses, would make an excellent team, whether it is interventional radiology, cardiology, or cardiac surgery. 

Has your use of the AngioVac had an impact on the growth of your own practice over the past five years? 

Having a pulmonary embolism response team has had a positive impact on my practice. Emergency physicians want to have patients with massive and submassive pulmonary embolisms moved ahead with treatment as soon as possible and are relieved that there is a team that is willing to always accept pulmonary embolism patients. Venous disease is an entity that has been underdiagnosed and undertreated. As referring physicians see the successful results that we are able to provide, we have seen an uptick in referrals. AngioVac is an important tool that has allowed us to treat patients effectively and as that knowledge is spread, we have have begun to receive repeat referrals and new referral sources.

How did you foster that spread of knowledge and resulting growth of your practice? 

A willingness to accept patients with limited treatment options has resulted in new referral sources both within and out of our referral network.  I have also found it important to include other practitioners from either vascular surgery, cardiology or interventional radiology in each case to generate interest and to avoid concerns regarding territory.  These patients bridge different specialties and I think that an inclusive rather than exclusive approach fosters strong team spirit and allows each patient to benefit from the additional skill sets that are brought to the table by different specialties.

What were some of the barriers you faced and how did you overcome them?

By building a team that is inclusive of all interested specialties, I think we have avoided many barriers that are generally the results of a lack of understanding and respect of each other. Interventionalists are more comfortable referring patients internally if they are able to participate in the case. I think our biggest barrier to generating referrals is the need for educating patients and other physicians that there are new treatment options available.

Can you tell us about the clot response team at Swedish Medical Center? 

Yes, this year we launched our formal pulmonary embolism response team (PERT). We have a phone number, (206) 320-PERT, to activate the team. We offer the service to local hospitals within our system, as well as hospitals within our region, as a service to treat any patient with pulmonary embolism. AngioVac is certainly an important piece of our treatment algorithm. The pulmonary embolism response team includes a group of surgeons and interventional radiologists that have access to aggressive therapy for pulmonary embolism. We offer a full range of services, from heparin therapy alone through catheter-directed thrombolysis, to AngioVac, and pulmonary embolectomy and even extracorporeal membrane oxygenation (ECMO). This is an organized group that tries to apply evidence-based therapy for patients with massive and submassive pulmonary embolism. 

What sorts of referrals are you seeing?

We are starting to get referrals from out in the community, from more distant hospitals, for patients that have deep vein thrombosis (DVT), occluded IVCs, even small pulmonary embolisms where heparin therapy is more than adequate, and our referrals have gone all the way up to unstable patients that require emergent therapy. Our volume of tricuspid endocarditis has also been increasing as a result of our willingness to treat these patients.

Does awareness of your program come through word of mouth or more direct advertising?

So far, it has been through word of mouth. We just launched our PERT in 2015 and will be starting our direct marketing program probably later in the year. As knowledge of our willingness to accept complex and high-risk patients becomes known and the results of our work have disseminated throughout the community, we are seeing more referrals from across the state.

What is the referral pattern in your hospital?

Our referrals primarily come from emergency physicians in the emergency department and from internal medicine physicians within the hospital. Patients within the hospital that come to us either have malignancies or have undergone orthopedic procedures and developed DVTs and potentially pulmonary embolism. Of course, we also have patients that come from outside the hospital through the emergency department. Both internal medicine physicians that are treating patients within the hospital and the emergency medicine physicians have found our service to be quite helpful. There are a number of pathologies that physicians do not want to have in their emergency departments or on their floors, and these include aortic dissections, aortic ruptures, and pulmonary embolism. Our physicians have found our service very helpful in risk assessing patients, and determining who might be a candidate to go home vs who requires heparin therapy, and which patients require advanced interventional therapy. Our team provides a rapid decision-making and treatment process.  

How was the response team started?

Three of us initiated the program, including myself (a cardiac surgeon), a critical care physician, and an interventional radiologist. We saw an unmet need to organize the treatment of these potentially unstable patients. We established algorithms that were evidence-based, and then brought in other team members, other cardiac surgeons, the rest of the members of the interventional team, the hospitalists, and the administrators, and launched the official program. We have been working on maturing our algorithms, looking at how to integrate hematology consultations and a hypercoagulable workup, along with integrating our services within the hospitalist team, the protocol care team, and the emergency department care team. Our work has been widely accepted, and physicians that have used the program to date have been very appreciative of the services we provide. 

Can you tell us more about the growth in referrals since beginning the program?

Before we had the program officially established, we would receive sporadic calls either to interventional radiology or directly to me. Since we have coalesced together as a team, the process has been working much more efficiently. Our PERT calls have increased quite considerably over the couple of months that we have been established, and certainly it has increased volume to the hospital for pulmonary embolisms. We have at least doubled our calls to date, since before the program began, and I would expect that as we move into more aggressive marketing that we will see these numbers double or triple.

The number of recognized patients with pulmonary embolism is quite low. Although physicians are very aware of prophylaxis, recognition of pulmonary embolism is still very challenging. It is often missed. Many physicians and medical professionals do not know the treatment options available beyond just anticoagulation. Sometimes practitioners think that the patient is too unstable for aggressive therapy and do not know who to call. Patients with DVT and occluded IVCs are even less recognized, but may have very significant problems with leg edema and leg discomfort. One of the goals of our PERT team is to increase awareness in the community about all these problems. In the community, especially in unstable patients, pulmonary embolism may remain a challenge, but certainly DVT and occluded IVCs are something that many patients suffer from. Both problems remain very poorly recognized and not well treated at this point in time. 

What do you envision as the future for the AngioVac device?

AngioVac has the potential to revolutionize therapy for tricuspid endocarditis. For occluded IVCs and iliac veins, it provides a very efficient and effective way of recanalizing the venous system, and can be used with adjunctive therapies to reestablish flow. For pulmonary embolism, although the use has been a little lower at the moment, with the newer generation device that easier to manipulate through the vasculature, it is going to be an ever-increasing opportunity. Most importantly, the AngioVac procedure is all done percutaneously, usually through a 26 French sheath and an 18-20 French return access. Sometimes an additional 6 to 8 French access is needed for some of the additional devices that can be used in conjunction with the AngioVac. We have also developed some techniques to help steer the device down into the iliac and femoral veins. Depending on the pathology, the aspiration cannula can be introduced through the right internal jugular vein to either femoral vein. The return can be any of the other major veins that are not used for aspiration. If we want to direct the cannula down deep into the pelvis or into the femoral veins, we can gain secondary access either in the popliteal veins or the femoral veins, and advance a balloon into the AngioVac cannula to help guide and steer the cannula down into the veins. This is a technique we have been developing and have presented at international meetings. 

As we accumulate and publish results of therapy with AngioVac, its utility will be further documented, which will lead to further increases in volumes.