A McCallie student who helped develop an innovative and improved way of treating strokes that are caused by a blood clot was featured along with his physician father at a meeting of the Chattanooga Engineers Club on Monday.
Christian Devlin, who is now a junior at McCallie, in 2009 helped make the discovery. After observing surgery done by his father in the stroke unit at Erlanger while he was still in middle school, he asked the question that led to the new process that is referred to as Neuron Protection System (NPS). The concept for the device, the procedure itself and the path leading toward putting it into practice was explained by Christian and Dr. Thomas Devlin at the club's weekly meeting.
Stroke is the fourth leading cause of death in the U.S., said Dr. Devlin, affecting 800,000 people yearly. It is also the number one cause of adult disability. It is very expensive causing financial and, most importantly, family hardships. Tennessee is in the “stroke belt” with higher than average occurrences of the disease due to smoking, diet and obesity at a young age.
The most common cause of stroke is when a blood clot blocks a blood vessel, restricting oxygen to the brain. “Time is Brain” is the descriptive phrase used for the speed that must be used for stroke treatments to be effective. Every minute the brain is deprived of oxygen supplying blood, two million brain cells die, so every minute counts, said Dr. Devlin. Until 1996 there was no treatment for a stroke. That year, a clot-busting drug became available that was injected into the vessel. It helped only 12 percent of patients. On the pathway to the clot, that medicine caused damage and bleeding.
In 2004 another treatment was devised called the Merci method which added the use of a catheter guided through the vessel to the clot in order to capture and remove it as the catheter is taken out. This method is effective but sometimes requires two-three hours and a lot of neurons are lost while blood-carrying oxygen does not pass beyond that location. Other methods used are vacuums or stent retrievers that are mostly used today to open up vessels to then pull out the clot.
Because of the future doctors program at McCallie, Christian Devlin saw this surgery take place and questioned if damage would be reduced if blood could be pumped through the clot before waiting to get it out, the way cardiac by-pass surgery is done.
That was a very good idea, said his father, who is chairman of Erlanger Hospital's division of neurology and director of the Southeastern Regional Stroke Center. This question was the beginning of implementation for the new stroke treatment.
Christian has partnered with his father and Dr. Blaise Baxter to bring this innovative procedure into use. They have worked and contracted with the catheter supplier, Advanced Catheter Technologies (ACT) to create a strong, flexible catheter capable of moving through the often small and twisted vessels where clots are found. The device is made up of a wire and an inner and outer catheter inserted in the leg. The wire is put in first, then the inner catheter followed by the outer catheter which stops when it has just passed through the clot. The wire and inner catheter are then removed, leaving the outer catheter which has a flexible tip and holes that allow life-saving, oxygenated blood to flow beyond the clot into the brain during the longer process of removing the blockage.
Some of the challenges in creating a catheter that have been met were achieving the correct pressure and volume of blood flow. There was also the realization that fresh blood must be used so that blood cells do not get damaged when passing through a long catheter. ACT has moved its company from Atlanta to Chattanooga because of the success this new technique promises.
Upon arrival at the emergency room, a patient is given physical examinations and dye is injected. Advanced imaging tests are performed within around 15 minutes of arrival to determine if the problem is a stroke and, if so, to pinpoint the location of the clot. At Erlanger, a senior brain physician is present around the clock to expedite treatment. Five to 10 stoke victims come to the emergency room daily. With the new NPS procedure, treatment could be started within minutes of arrival, with the process of restoring blood flow taking roughly only five minutes to complete. It was noted that the time it takes a patient to get to the emergency room is where most time is lost.
The way NPS works is that after the catheter is in place and blood is flowing with the help of a pump, medicine used to dissolve the clot would then be administered through the same catheter directly into the clot eliminating many of the problems caused by the previous technique of it passing throughout the blood vessel. When it begins to dissolve, a fibrous net, that also is passed through the same catheter, is used to capture and remove the clot as the whole device is retracted.
Other matters will factor into the success rate of the NPS. Better drugs are needed to reduce bleeding, and the use of stem cells is seen as a way to grow new vessels after the procedure. Infrared technology is used to sense oxygen levels in the brain so doctors can know when it needs to be raised during surgery. Blood viscosity is also important in this procedure and can be adjusted with blood thinners, and cooling the blood is beneficial to slow down the brain’s use of oxygen.
Quest, the company manufacturing the pumps used for the NPS device, is developing a portable version with hopes that trained EMT responders would be able to insert the catheter and hook it up to the external pump in stroke patients to restore blood flow and reduce damage, before arrival at a hospital.
The patent for this device and treatment was received just last week. Approval for use is anticipated to be gained soon. Bench testing is now being done, and animal testing will be done in the next three-six months, and human testing is expected next year.
Dr. Thomas Devlin
- Photo2 by Gail Perry