Water, first a drip and then a stream, carved the Grand Canyon, blazed the liquid highway that is the Mississippi River and now clears blood clots clogging human arteries.
The AngioJet, made by Minneapolis-based Possis Medical, uses water power to melt away dangerous clots from inside diseased vessels. Already approved by the Food and Drug Administration for clearing vessels tapped regularly during dialysis, the AngioJet is expected any day to get the regulatory green light for clearing clots from the arteries that nourish the heart. Worldwide, Possis estimates as many as 500,000 patients a year may ultimately benefit from the treatment. About 200 AngioJet machines are already installed in the U.S.
Blood clots often form in coronary arteries during heart attacks or other cardiac crises, like unstable angina, that can lead to them. Tapping a burgeoning bag of plumbing tools, interventional cardiologists stand ready to snake balloon catheters, fancy Roto-rooters or stents inside the troubled vessels to clear fatty plaques at the root of most heart problems.
First, though, they must sometimes remove a blood clot, a fibrous plug that caps the side of the fatty obstruction facing the flow of blood. The clots can form when blood flow is disturbed by an obstruction in the vessel. Without warning the clot may come apart, a risk heightened during intervention, sending dangerous pieces drifting through the body. Those fragments can bottle up small vessels of the brain, causing a stroke. Sometimes the bits of clotted blood don't make it that far. The fragments can stick further down the coronary vessel or inside the heart, triggering a full-blown heart attack.
When serious heart trouble strikes, cardiologists usually order an angiogram. In as many as 4% of cases, a blood clot appears on the X-ray images. Although hard data are difficult to come by because many clots don't show up on X-rays, the rate of significant clots may approach 25%, some cardiologists say.
When a clot is seen, or strongly suspected, doctors usually prescribe an intravenous blood thinner, such as urokinase or ReoPro, to dissolve the plug. ReoPro, often running $1,400 per case, and urokinase, at $1,000 to $2,000, are notorious hospital budget-busters. Beyond the hefty drug bills, patients must be hospitalized for a day or two while the blood thinners are slowly infused, further running up costs. And the blood thinners, though generally effective, can cause hemorrhaging and other complications.
Enter the AngioJet, which has roots in industrial-strength water cannons used to cut the turbine blades of jet engines.
The end of the AngioJet is a catheter that relies on the Bernoulli principle, which, for those who've forgotten their high school physics, explains the creation of a low-pressure zone next to a stream of fast-flowing fluid. The same invisible force helps lift the curved wing of an aircraft slicing through air. But in the AngioJet several micro-fine jets arranged like a shower head shoot saline solution backward through the catheter at half the speed of sound, creating a powerful suction that removes blood clots in minutes while sparing delicate vessel walls.
Besides invoking a gee-whiz reaction, the AngioJet also saves money compared with drug therapy. Over the course of a year, the cost of treating a patient with urokinase averages $28,077. That compares with $23,268 with AngioJet, according to results of a cost-effectiveness study to be presented at the American College of Cardiology this week.
"In five years, I've never done an economic analysis that's as favorable as this one," says David Cohen, M.D., principal author of the cost-effectiveness study and assistant director of interventional cardiology at Beth Israel Deaconess Hospital, Boston.
The AngioJet won by reducing catheterization laboratory expenses, length of stay and complications.
Although the savings with AngioJet may be less dramatic compared with ReoPro (a more recent entry in the blood-thinner market), Cohen says, he still believes they would be significant.
Even so, the AngioJet is unlikely to completely displace clot-busting drugs. At Beth Israel Deaconess, for instance, only about 40 or 50 of the 1,500 patients undergoing cardiac intervention are slam-dunk candidates for treatment with the device. Nonetheless, Cohen says the AngioJet pays for itself when used on as few as two patients per year, assuming the device is in service for five years.
The AngioJet console costs $25,000 and the disposable supplies run about $1,450 per cardiac case, according to Possis.
"It's not that big of an expense, and the upside is very big," Cohen says.
Still, some people question whether such a niche product is worth the administrative and clinical effort.
Hospitals should ask, "Do I have enough patient volume to get involved in this and (to) keep the (clinical) skills up?" says Anthony Montagnolo, a vice president at ECRI, a not-for-profit technology assessment firm based in Plymouth Meeting, Pa. Sometimes an effective but limited device can sit idle for months between uses, he says, and "it may not be a huge waste of money but is a waste in terms of energy and opportunity costs."*q