Physician's Weekly Article - Stroke: Taking a Targeted Approach

       New targeted technologies are creating more options for patients who fail to receive early stroke care or who do not respond to tPA treatment.

      Tissue plasminogen activator (tPA) is a thrombolytic agent approved for use in certain patients having a stroke. The drug dissolves blood clots and has been shown to be effective in treating ischemic stroke, the kind that is caused by blood clots which block blood flow to the brain. In 1996, the FDA approved tPA for use when treating ischemic stroke in the first 3 hours after the start of symptoms. “For many stroke sufferers, tPA can mean the difference between permanent brain injury or recovery,” says Demetrius K. Lopes, MD, “but only if patients receive intravenous tPA within that 3-hour window of the first symptoms. Unfortunately, research shows that less than 5% of stroke sufferers get tPA within that specified timeframe.”

      Dr. Lopes notes that tPA is frequently poorly utilized because patients often do not get the specialized care they need in time. “One of our main problems with stroke is that symptoms are not straight-forward. Patients usually don’t experience pain and will often wait for numbness or speech alterations to dissipate. The symptoms are frequently ignored by patients.” In addition, of those treated with tPA, the drug only helps about 30% of patients, either because the clot is too large or too difficult for the drug to dissolve. Further complicating the use of tPA is that the drug is associated with a higher risk of bleeding.

      Big Strides Being Made

      In light of issues surrounding the timing of tPA administration, significant investments in improving care for stroke have occurred within the past several years. Clinicians are assessing new strategies that may make a substantial impact on the disease. “We’re going through a brain attack revolution right now as we’ve gained a better understanding of the condition,” Dr. Lopes says. “In addition to the development of interventions to prevent recurrent stroke, several acute interventional stroke therapies have recently emerged [Table 1]. The concept of mechanical thrombolysis has also given new hope for patients. Instead of injecting blood thinning medications, we now have the capability to remove the clot from the vessels.”

      A number of mechanical thrombolysis tools have been assessed for treatment of acute stroke, including suction-creating saline jets, laser energy, ultrasound, and corkscrew devices. “The FDA’s approval of the Mechanical Embolus Removal in Cerebral Ischemia (Merci, Concentric Medical) retrieval system, a corkscrew-like apparatus, is important to improving stroke care because it increases the window for treatment to 8 hours and is effective for people who don’t respond to tPA. The Merci Retriever removes blood clots from the brain in patients experiencing an ischemic stroke.” The corkscrew resides in the catheter tip, shielding it from the wall of the vessel until it is ready to be burrowed into the clot. Once entered into the clot, the Merci Retriever and clot are then withdrawn from the vessel.

      New Device Promising

      A new FDA-approved device called the Penumbra System (The Penumbra System, Inc.) is another endovascular advance designed to assist recovery from stroke. With this system, a tiny tube is threaded inside a blood vessel at the groin and pushed through the body and into the brain until it reaches the clogged artery. Similar to a vacuum cleaner, it sucks up the clot piece by piece to restore blood flow. “The Penumbra system appears to be an emerging treatment option for patients who miss out on early care,” Dr. Lopes says (Table 2). “It can be used up to 8 hours after a stroke strikes or if standard tPA treatment fails.” To date, only a few hospitals in the United States have tested the Penumbra system, but Dr. Lopes says that it has the potential to produce dramatic results when used in appropriate patients. “In our early experience, the device has caused few serious side effects. About 42% of successfully treated patients showed significant recovery when measured a month later.”

      A Delicate Balancing Act

      While having newer devices to treat stroke is encouraging, Dr. Lopes warns that researchers are still working to determine which patients are good candidates for the Penumbra System and other mechanical thrombolysis tools. “Unclogging a blocked brain artery isn’t always the best option,” he says, “because it can sometimes do more harm than good in severe strokes. When the dam is broken and blood rushes into oxygen-deprived brain tissue, swelling or a brain hemorrhage can be triggered, which can be deadly. It’s important to consider the treatment balancing act. We need to determine if we can use brain scans to estimate if the stroke already has killed all the brain tissue it’s going to kill, or if enough tissue can be salvaged. We have good devices; now, we need to learn how best to use them.”



      Demetrius K. Lopes, MD has indicated to Physician’s Weekly he has worked as a paid speaker for Boston Scientific, Microvention, Cordis, Micrus, and EV3. He has also received grants/research aid from Boston Scientific, EV3, Micrus, Microvention, and Cordis.