So with the 88% failure rate of tPA full recovery maybe other options exists. But since we have NO stroke leadership or strategy nothing will occur to solve this problem. It has been 21 years since this failure has been known, I don't expect anything to change for the next 21 years unless a lot of people die that are preventing new ideas from being considered.
Magnetic nanoparticles to direct tPA to the clot, size of bolus could be reduced lowering bleeding risk.
Future of med devices: Nanorobots in your blood stream
Use them to deliver tPA or drill thru the clot.
Why the Go-To Stroke Drug Can Fail
Twenty years ago stroke doctors celebrated the arrival of a powerful
new weapon: the clot-clearing drug tPA. It was hailed as a lifesaver and
has proved to be one for hundreds of thousands of patients since. TPA
was the first and is still the only medicine approved by the U.S. Food
and Drug Administration for treating strokes caused by clots that block
blood flow to the brain. But like so many medical marvels, tPA (which
stands for tissue plasminogen activator) has turned out to have serious
limitations. It needs to be administered within three hours of symptom
onset, does not last long in the body before it loses effectiveness, can
cause uncontrolled bleeding and often fails to break up large clots.
For many of the nearly 800,000 Americans who every year suffer ischemic strokes, as the brain blockages are called, these shortcomings can be deadly. Nearly 130,000 die. Sadly, there have been no good alternatives to tPA since it debuted.
Recently doctors and scientists have broken this long-standing clinical stalemate with new tools to put a dent in those grim numbers. One innovation, a tiny wire device called a stent retriever, can be snaked up into the blood vessels leading to the brain to pull out large clots. “It's the first proven, effective treatment for acute stroke in a generation,” says Jeffrey Saver, director of the Stroke Center at the University of California, Los Angeles. Approved by the FDA in 2012, the stent retriever got a boost this year when the journal Stroke reported data showing many more patients treated with a retriever resumed normal life than did patients who received tPA. (The retriever manufacturer, Medtronic, provided support for the studies. Neurologist Bruce Campbell of the Royal Melbourne Hospital in Australia, who co-led the analysis, notes that Stroke has “strict independent-peer-review processes” to guard against bias.) Researchers are also developing better clot-detection scans, as well as a technique involving magnetism that guides tPA directly to the problem. This method could help eliminate dangerous obstructions elsewhere in the body, as well as in the brain.
This is where the stent retriever has an advantage. It is a narrow tube that can be threaded up from the femoral artery in the leg to the site of the clot. Then wire mesh on the end of the retriever, which expands like an accordion, is pushed into the clot. The mesh tendrils keep the clot from breaking apart in the brain—which could be deadly—and help separate it from blood vessel walls. The device is next pulled out of the body, and the clot comes with it. (In years past, doctors had tried a device with a corkscrew tip but found it was not as good at clearing the clot.)
Another advantage the device has over the drug is that the time window for the use of the stent retriever after symptoms arise is double that of tPA—six hours instead of three. The Stroke analysis found that blood flow in a vessel blocked by a large clot was successfully restored in 236 of 306 patients, or 77 percent, treated with the stent retriever. With tPA alone, the success rate was around 37 percent.
Like all surgical interventions, the stent retriever carries the risk of complications. The main one is bleeding, which is why patients with high blood pressure and the strained vessels that go with it may not be candidates for the procedure. “There's also a chance of the guide wire or some other manipulation of the device poking through the blood vessel during the procedure,” Saver says.
A much less common complication, Saver adds, is a piece of the clot breaking off as it is being pulled out, escaping into a new artery and causing a new stroke in a different area than the initial one. It happens in about 2 to 3 percent of cases, he says
For many of the nearly 800,000 Americans who every year suffer ischemic strokes, as the brain blockages are called, these shortcomings can be deadly. Nearly 130,000 die. Sadly, there have been no good alternatives to tPA since it debuted.
Recently doctors and scientists have broken this long-standing clinical stalemate with new tools to put a dent in those grim numbers. One innovation, a tiny wire device called a stent retriever, can be snaked up into the blood vessels leading to the brain to pull out large clots. “It's the first proven, effective treatment for acute stroke in a generation,” says Jeffrey Saver, director of the Stroke Center at the University of California, Los Angeles. Approved by the FDA in 2012, the stent retriever got a boost this year when the journal Stroke reported data showing many more patients treated with a retriever resumed normal life than did patients who received tPA. (The retriever manufacturer, Medtronic, provided support for the studies. Neurologist Bruce Campbell of the Royal Melbourne Hospital in Australia, who co-led the analysis, notes that Stroke has “strict independent-peer-review processes” to guard against bias.) Researchers are also developing better clot-detection scans, as well as a technique involving magnetism that guides tPA directly to the problem. This method could help eliminate dangerous obstructions elsewhere in the body, as well as in the brain.
Big Clots, Big Trouble
Of all of tPA's drawbacks, the most troublesome is its inadequacy against big clots, which can block large blood vessels at the base of the brain; they cause about 25 to 30 percent of all strokes. Although it works well against smaller clots in narrower vessels, a safe dose of the drug—which is delivered intravenously—often does not last long enough in the bloodstream to dissolve the big clots, and increasing the dose raises the risk of bleeding. “All you need to see is one intracranial bleed from tPA, and you realize you've got to pause before you give that medication,” says Thomas Maldonado, a clot specialist at New York University's Langone Medical Center.This is where the stent retriever has an advantage. It is a narrow tube that can be threaded up from the femoral artery in the leg to the site of the clot. Then wire mesh on the end of the retriever, which expands like an accordion, is pushed into the clot. The mesh tendrils keep the clot from breaking apart in the brain—which could be deadly—and help separate it from blood vessel walls. The device is next pulled out of the body, and the clot comes with it. (In years past, doctors had tried a device with a corkscrew tip but found it was not as good at clearing the clot.)
Another advantage the device has over the drug is that the time window for the use of the stent retriever after symptoms arise is double that of tPA—six hours instead of three. The Stroke analysis found that blood flow in a vessel blocked by a large clot was successfully restored in 236 of 306 patients, or 77 percent, treated with the stent retriever. With tPA alone, the success rate was around 37 percent.
Like all surgical interventions, the stent retriever carries the risk of complications. The main one is bleeding, which is why patients with high blood pressure and the strained vessels that go with it may not be candidates for the procedure. “There's also a chance of the guide wire or some other manipulation of the device poking through the blood vessel during the procedure,” Saver says.
A much less common complication, Saver adds, is a piece of the clot breaking off as it is being pulled out, escaping into a new artery and causing a new stroke in a different area than the initial one. It happens in about 2 to 3 percent of cases, he says
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