During both types of thrombolysis, doctors use radiologic imaging to see if the blood clot is dissolving. If the clot is relatively small, the process may take several hours. But treatment for a severe blockage may be necessary for several days. Doctors also may opt for another type of thrombolysis called mechanical thrombectomy. During this procedure, a long catheter tipped with a tiny suction cup, rotating device, high-speed fluid jet, or ultrasound device is used to physically break up the clot.