(Undated) -- A study called "Mr. Clean" is showing promising results for the most severe stroke patients. Results show using a catheter-based treatment within six hours of a stroke is effective and safe. Doctor M. Shazam Hussain treats stroke victims. An ischemic [[ ih-shem-ick ]] stroke happens when an artery is blocked to the brain. Standard care is to give the patient clot-busting medications, but when the clot is large enough it's difficult to fully open the artery, so doctors use a catheter-based method instead. Researchers in The Netherlands studied the effects of catheter-based treatments and found patients showing improved function after 90 days.