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Tiny nozzle shoots saline, pulverizes thrombi
The Food and Drug Administration (FDA) gave a quick nod in March to a new clot-busting device that uses tiny jets of saline to break up and suction away blockages in coronary arteries. Especially beneficial for patients who can’t take blood thinners due to bleeding disorders, the AngioJet Rheolytic Thrombectomy System (Possis Medical, Minneapolis) serves as an alternative to thrombolytic therapy as well as adjunctive therapy pre- or post-angioplasty. The system has already won FDA approval for the removal of clots in patients undergoing kidney dialysis.
The system has three components: a reuseable drive unit that costs about $35,000, a disposable single-use pump set, and catheter that costs $1,450. (See photo of the system, p. 100.) Rheolytic thrombectomy is a one-day procedure as opposed to the all-day and overnight hospital stay needed for thrombolytic therapy.
Avoiding open-heart surgery
The minimally invasive device is best suited for the patient who has had multiple heart attacks and still has one or more large arterial blood clots. Since clot formation, the patient may have experienced angina after only minor physical exertion, with an adverse effect on his quality of life. For that patient, rheolytic thrombectomy with balloon angioplasty or stent placement could avoid open-heart surgery.
"Rheolytic thrombectomy is a good treatment for the acute infarction patient — one who’s had a bypass in the past but still has a large chunk of blood clot in a vessel," says Gina Marone, RN, BSN, clinical study coordinator at Allegheny University Hospital-Hahnemann Division in Philadelphia.
The pump-driven system is fed through the femoral artery directly to the area of the blood clot. A tip at the end of a catheter sucks in clots where they are pulverized by the force of the liquid, then drawn back up the tube and into a receptacle.
The snake-like 140-cm catheter has a double lumen design. One lumen contains a stainless steel high-pressure tube that delivers saline to the tip; the other larger exhaust lumen is for the removal of thrombus debris. The first tube is formed into a loop at the distal catheter tip. The underside of the loop has jet holes that are directed backward into the exhaust lumen. The high velocity jets create a localized low-pressure zone that draws the thrombus into the tip. The jets break up the thrombus and provide the driving force to push debris down the exhaust lumen into a collection bag.
Treatment takes about a minuteM
Treatment takes about one minute, and once the blood clot is removed, interventional cardiologists can proceed with balloon angioplasty in the same setting. The system requires mild IV sedation rather than the general anesthesia that would be required with bypass surgery.
"The procedure lasts about a minute, and the vacuuming by itself takes about 40 seconds," says Marone. "We numb the groin, then when we activate the device we give a relaxing drug cocktail and tell patients they’ll get some chest pain and not to worry." All patients undergoing such treatments are premedicated.
Before AngioJet was approved by the FDA, Daniel McCormick, DO, principal research study investigator at Hahnemann, and Marone used the system in research studies at Allegheny. In Marone’s opinion, rheolytic thrombectomy saves money in certain circumstances: "The choice is case-specific. There are antiplatelets on the market such as abciximab (Eli Lilly’s ReoPro) that decrease platelet stickiness so clots don’t adhere; but for large chunks of clots, especially in a bypass graft, this device works well. Antiplatelets work well with straight primary angioplasty and stenting." And not all patients can take antiplatelets.
A recent economic study that was presented at this year’s annual American College of Cardiology conference compared the rheolytic system to therapy with urokinase (Abbott Park, IL-based Abbott Laboratories’s Abbokinase) and reported that rheolytic thrombectomy saved more than $3,500 per patient in reduced hospital stays, doctors’ fees, and other costs.1
Investigators looked at inhospital and one-year follow-up costs for 349 patients with thrombus-containing lesions. Participants were randomized to treatment with either of the two modalities, and investigators found the use of the AngioJet system saved $3,555 when compared with the cost of prolonged urokinase during the initial hospitalization. (See chart, above left, showing initial hospital costs.) Three major savings factors were:
• shortened length of stay — 4.2 days vs. 5 days (see bar graph, above right);
• reduction in periprocedural infarction and bleeding complications — $3,519 and $5,997, respectively;
• need for a single catheterization for most rheolytic patients — $2,460.
Compared to standard treatment with urokinase, the study authors concluded, rheolytic thrombectomy both improved clinical outcomes and reduced overall costs.
But is rheolytic thrombectomy as effective and safe as the traditional drug for treating these patients? The same group of researchers ran a trial testing that, and concluded that, yes, the two techniques are equally effective, and that the mechanical technique is significantly safer.2
AngioJet patients had a significantly higher procedure success rate and a lower complication rate than the urokinase patients. Freedom from major adverse cardiac events persisted for up to one year in the rheolytic thrombectomy group. (See bar chart, p. 102, showing major adverse events to 30 days.)
New catheters still being tested
"Possis has FDA market approval for this vacuum device," says Marone, "but we’re still running trials on other new catheters that the company is developing." Marone told Cost Management in Cardiac Care that there is no other product available that accomplished the same task as AngioJet.
"The only product that somewhat compares is a balloon occlusion device that’s not yet FDA approved," says Marone.
The Guardwire balloon occlusion system is still under investigation by cardiologists at Rush-Presbyterian-St. Luke’s Medical Center in Chicago. With that system, a small, flexible wire with an inflatable balloon at the tip is advanced through the catheter, past the blockage to the site where the bypass vein meets the coronary artery. It works by sealing one end of the bypass graft with a balloon to prevent the debris produced during an angioplasty from floating downstream into the coronary artery.
A second balloon is inflated at the site of the blockage, pressing the material that caused the blockage against the vessel wall within the bypass graft to restore blood flow to the heart. A low-pressure vacuum aspiration catheter is threaded along the guide wire to draw out remaining debris from inside the vessel.
Avoiding angioplasty in old grafts
The Guardwire system seems best suited for patients with previous bypass grafts.
"Physicians have avoided the use of angioplasty in patients with diseased, old, bypass grafts because of the serious complications that can arise when debris dislodges during angioplasty and then blocks a coronary artery downstream," said Jeffrey Snell, MD, associate director of interventional cardiology at Rush in a press release. "Unlike plaque that narrows or blocks a coronary artery, a combination of friable plaque and organized blood clots narrow a bypass graft. This material often breaks loose when an angioplasty balloon is inflated in the bypass vein graft."
Other devices that serve as alternatives to open-heart surgery and that increase the effectiveness of angioplasty procedures are the Guardian system manufactured by Radiance Medical Systems in Irvine, CA, and another manufactured by Percusurge in Sunnyvale, CA.
Marone says that what she and McCormick liked about the AngioJet was that "it’s very site-specific. It evacuates clots very effectively. In all the cases we saw, there was definite improvement with total evacuation of the thrombus."
1. Cohen DJ, Cosgrove R, Berezin R, et al. Cost-effectiveness of rheolytic thrombectomy for thrombus-containing coronary lesions: Results from the VEGAS 2 Trial. Presented at the 48th annual Scientific Session of the American College of Cardiology. New Orleans; March 1999.
2. Ramee SR, Baim DS, Popma JJ, et al. A randomized, prospective multicenter study comparing intracoronary urokinase to rheolytic thrombectomy with the Possis AngioJet catheter for intracoronary thrombus: Final results of the VeGAS 2 trial. Circulation 1998; 98:I-86.
• Wagner H, Muller-Hulsbeck S, Pitton MB, et al. Rapid thrombectomy with a hydrodynamic catheter. Radiology 1997; 205:675-681.
• Koning R, Cribier A, Gerber L, et al. A new treatment for severe pulmonary embolism. Circulation 1997; 96:2,498-2,500.
• Nakagawa Y, Matsuo S, Yokoi H, et al. Stenting after thrombectomy with the AngioJet catheter for acute myocardial infarction. Cathet Cardiovasc Diagn 1998; 43:327-330.
• Kim R, Fischman DL, Dempsey CM, et al. Rheolytic thrombectomy of chronic coronary occlusion. Cathet Cardiovasc Diagn 1998; 43:483-489.
• Nakagawa Y, Matsuo S, Kimura T, et al. Thrombectomy with AngioJet catheter in native coronary arteries for patients with acute or recent myocardial infarction. Am J Cardiol 1999; 83:994-999.