May 09, 2016 11:49 AM

Setting a Trap to Treat Stroke

Plucking a blood clot from the brain with a tiny wire trap is proving highly effective when a stroke hits — with quicker recovery and improved long-term results.

A surgical method to ensnare and remove debilitating blood clots with technology known as a stent retriever has helped some ischemic stroke patients recover quicker and more fully after symptoms strike.

Inserted through an artery (typically in the groin), the collapsed stent can be expanded from inside a catheter once routed up to the brain’s blocked blood vessel. A wirelike cage then “traps” the clot and ushers it out of the body. Catheter-based suction is also applied to improve the efficiency of the stent retrievers to open a blocked brain vessel.

Using a 2-millimeter incision, the minimally invasive procedure takes about 60 to 90 minutes in most cases.

But results often are more immediate for stroke patients at high risk of losing brain cells — and, as a result, permanent loss of functions — when vital oxygen carried in the bloodstream is deprived.

“Their function improves right there on the (operating) table; that is the most exciting part of the whole thing,” says Neeraj Chaudhary, M.D., an assistant professor of radiology and neurosurgery at the University of Michigan.

Many, he adds, “start talking, start moving their hands and legs” shortly thereafter. “It’s huge, absolutely huge.”

Growing usage and recognition

Two stent-retrieval devices, Solitaire and Trevo, were approved in 2012 by the Food and Drug Administration.

Although the technology has been available since then as part of the Neuro-Interventional Radiology/Surgery portion of U-M’s Comprehensive Stroke Program, it has found wider adaptation and recognition nationwide since five studies on the procedure were published in 2015 in the New England Journal of Medicine.

And the American Heart Association endorsed the stealth technique, also known as thrombectomy, in a series of new guidelines released last June.

At U-M, Chaudhary says, the number of stroke patients treated last year with stent retrievers increased to about 50 — an uptick of 50 percent over prior years. He expects that number to climb.

“The U-M motto is to practice evidence-based medicine,” Chaudhary says. “It has become the stamp of approval.”

"Their function improves right there on the (operating) table; that is the most exciting part of the whole thing."
Neeraj Chaudhary, M.D.

Positive outlook

Stent retrievers could mark the biggest development for stroke patients since the FDA approved a tissue plasminogen activator (tPA) in 1996.

Even if receiving a stent retriever, a patient likely will be given tPA — a clot-dissolving medication — as a first line of defense.

But tPA, Chaudhary says, is only effective if administered within 4½ hours of the onset of stroke symptoms (many people ignore or fail to recognize common stroke symptoms and don’t go to an emergency room in a timely manner).

“Stroke does not cause pain; it causes disability,” Chaudhary says. “If it did cause pain, people would be coming to the hospital sooner.”

The intravenous tPA medication, he adds, is effective in dissolving clots with improved outcome in about 30 to 40 percent of ischemic stroke cases.

Stent retrievers, which can be inserted up to six hours after a stroke hits, can open blocked vessels 80 to 90 percent of the time — with “improved outcome” in 50 to 60 percent of patients after their discharge, Chaudhary says.

At present, thrombectomies represent a small fraction of treatments for the estimated 690,000 ischemic strokes annually in the United States.

Covered by Medicare and Medicaid, the procedure costs about $10,000, according to the American Heart Association — which also estimates that strokes, the fifth leading cause of death in the United States, cost the nation $71.6 billion in related medical expenses in 2012.

As the technology has been tied to better function and faster recovery, the upfront expense could trump lifelong costs of caring for a person otherwise disabled by stroke.