Large-Diameter Catheter for Pulmonary Embolism: An Interview with Christopher Kwolek, MD

At the 2012 VEITHsymposium, Christopher Kwolek, MD, gave a presentation describing the use of the Vortex AngioVac Suction Cannula for pulmonary emboli removal (AngioDynamics). The AngioVac device has been FDA approved for removal of intravascular material from the venous system. It uses a suction device to remove large thrombi and then filters out blood and returns it to the patient. Vascular Disease Management spoke with Dr. Kwolek about new developments for the system.

Q: Could you give us an overview of the goal of your presentation on the Vortex catheter system?

A: Pulmonary embolism is a national concern. Many times these patients are young, relatively healthy patients who have catastrophic life threatening emboli.  Although we want to be aggressive, the therapies have their own risks and benefits, so any time there are several ways to treat something, often it means we’re in an evolving process trying to figure out what’s going to work best for each patient and how we can tie different therapies together.

Q: How did you first get involved in using the Vortex system?

A: I am a vascular surgeon by training, but I was attending a cardiothoracic surgical conference and heard a presentation about a new device designed to remove clots from the venous system. While the initial intent was to remove clots that had traveled from the legs and the abdomen up to the heart and lungs, it became clear that it would be useful for removing clots anywhere along that pathway before they reached the heart and the lungs. And that’s where I became involved. 

At that time, Vortex was a very small start-up company started by a heart surgeon who had trained at Brigham and Women’s Hospital in Boston, Dr. Lishan Aklog. Because I work at Massachusetts General, another Harvard-affiliated hospital, we began talking and it became clear that there was a lot of opportunity for synergy and working together, so I became involved in helping to develop tools and adjuncts for the system and gained more experience with it. What we found was that the benefit of this type of device is that it is a very large-caliber clot removal system hooked up to a centrifugal pump which not only allows you to remove the clot and also blood along with it, but then the filter removes the clot and the blood retruns to the patient.

The other thing that’s different is that it allows you to remove the clot in large pieces rather than trying to morcellate or fractionate the clot to get it to come out through tiny catheters. 

Also, when we have a very large clot, particularly in the veins, we can certainly put a catheter in and try to use clot-busting drugs to break it up, but that takes time, and in many cases we don’t have the luxury of time if the circulation is clotted off. Adjunctive measures to speed up that process can have their risks, such as higher doses of clot-busting medicine that can lead to bleeding problems, or breaking the clot up mechanically, which can damage the vessels and there have also been cases where mechanical lysis of the clot can harm the kidneys and cause acute renal failure.  

The concept of going in with a large-caliber suction to remove the clot in one piece or several pieces has a lot of merit to it, and certainly from a response and from a hemodynamic standpoint, to be able to do that and restore flow very quickly has a lot of merit, too. So we started using this about 2 years ago with patients who weren’t good candidates for the other procedures. We treated patients who had massive clots and who were often in danger of losing their leg or their life. The first  8 patients did remarkably well. We were able to remove clot from the iliacs and inferior vena cava and get the inferior vena cava back open. None of those patients lost their leg or their foot. 

We’ve started expanding this to other areas – for removing masses that are attached to catheters or heart valves, and also for the initial indication for clots that have traveled out into the branches going to the pulmonary arteries.

One of the limitations today has been that because it’s a small company they have been limited with manufacturing, distribution, and developing new prototypes.  There were initially 50 cases and now there are approximately 375 or 400 cases, but the device is limited in the sense that it needs improvement in terms of flexibility, adjunctive catheters, and other things to help with the procedure. Recently this small company was purchased by Angiodynamics, which has an expertise and interest in vascular disease and catheters, so hopefully this will be a good synergy that will allow this to continue to improve. 

We really don’t know where this is going to fit into the big picture but it’s easy to imagine how useful it is for someone to have access to a device that can remove clots, tumors, and other foreign materials and retrieve them quickly.

We have noticed that it works better on clot that is fresh or new, within the first three months. We have had patients with clots for a longer time where it has become adherent and ingrown into the vessel, and in those cases I’m not sure anything short of cutting it out will work.

 Q: Do you have a case example that was particularly remarkable?

A: I just saw someone in my office last week who was active, in her 40s, and exercised. She came in for knee surgery, the type of thing you go home a day or two after, and afterward she had some swelling in her leg on the left side and subsequently was found to have a blood clot in the left leg. Despite the fact that she was on blood thinners, the clot progressed. It led to her entire left leg and hip and pelvis becoming swollen. When I saw her she was in a lot of pain. She did not have a pulmonary embolus, she had thrombosis of the IVC going down to the leg with phlegmagia -- the venous flow was so obstructed it caused blood going into the leg to back up. Phlegmasia can at times lead to massive swelling, edema, ulcers or sores, or even loss of a leg. 

We tried to go in with the standard catheter, but she had a critical stenosis at the origin of the left common iliac vein due to extrinsic compression from the artery — May-Thurner syndrome — so we ended up taking her to the operating room, and with a small incision we cleaned out the clot in the groin. Then using the Vortex suction thrombectomy catheter, we removed the clot all the way up to the inferior vena cava. We put in a temporary retrieval basket from one of the other blood vessels first so that while we were doing the work with the catheters, we minimized the chance of a piece breaking off and tracking to the heart and the lungs. We were able to get through the procedure successfully, we found the area where the vein had been narrowed by the artery, and we also used an ultrasound catheter to visualize it, and we placed a stent and put her on blood thinners. We found that she had a hypercoaguable state, so it was a perfect storm:  the compression, the recent surgery, maybe something about her blood that made it more likely to clot; but we were able to clear that all out, and a month later her leg was almost back to normal. Just last month we went back in and removed the umbrella filter, and now she’s back to her baseline and walking – still on a blood thinner but much happier and much more functional than if we had done the traditional heparin shot, blood thinners, give her some stockings to wear and see how she does for 2 to 3 months. Many of those patients will come back with a chronically swollen leg and 5 or 10 years down the road come back with chronic edema and varicosities at best but at worst skin changes, ulcers, sores. So that’s a perfecgt example of having a high index of suspicion in a young otherwise healthy patient, and aggressively trying to clean out that clot. That makes a huge difference not only in the short term, but also in terms of where she’s going to be 5, 10, or 15 years down the road. 

Q: What is the status of the product? Will it soon be reaching more providers?

A: This process has been FDA approved for several years for the removal of clots, tumors, masses, the direct indication is removal of undesirable intravascular material from the venous system. It’s commercially available and the interesting thing is that the company was started in the United States. Many times these days, companies will go overseas because of the challenging regulatory process to get things approved in the United States, this is one of the few devices that was started here in the last 5 years and kept here predominantly for use, and it’s about to start expanding overseas but all of the early experience has been within the United States. Now that there’s a larger group there’s a possibility of more efficient distribution, but jut as importantly for further work on developing additional tools and adjuncts that will help it to be useful. 

Q: What is the most important takeaway for the vascular specialist about this catheter?  

A:  I think the idea of moving toward a multidisciplinary team of people with different backgrounds working together to try to address complex issues like pulmonary embolus is important. As the device currently stands, it can be used percutaneously or through a cutdown. So someone with interventional skills, surgical skills, imaging skills, can all be helpful. In addition, the way the system is used with a pump it can be helpful to have someone who has technical skills and experience like a technician who is used to working with heart pumps and those types of things either in a catheterization lab or surgical suite so it does lend itself to having several people from different backgrounds involved. So it’s something that could and would be available at centers that had the capability of using a partial bypass pump – it’s not the same as open-heart surgery in terms of hemodynamics and so on, but it certainly does lend itself to that team approach because it it a step above in terms of complexity compared to a stent procedure. 

Q: So you are working on a multidisciplinary team now? 

A:  Often in a big institution, there may be many patients who come in with variations of the same process, and different specialists might be called on different days. We felt that in this area there is clearly a benefit to getting mutliple people involved early on to discuss the patient and the right therapy for them. Certainly for complex patients like this I think it’s important. And just like any health care awareness campaign, knowledge is key, and by letting patients and practitioners know about their options you increase awareness. Many times, particularly for clots in the leg, the traditional therapy is to put them on blood thinners and let them go and see how they do. Even for minor pulmonary emboli, at least we need to ask the question, when should we be more aggressive. If we come up with standardized and improved ways to do that within a center I think there’s a great benefit to that.  

Christopher Kwolek, MD, serves as director of the vascular and endovascular training program at the Massachusetts General Hospital and as the chief of vascular surgery at Newton Wellesley Hospital. He is recognized by Castle and Connolly and Boston Magazine as one of America’s Top Doctors. Dr. Kwolek reports that he is on the medical advisory board for Vortex Medical.