Although thrombolysis is usually successful, the treatment is not able to dissolve the blood clot in up to 25% of patients. Another 12% of patients subsequently redevelop the clot or blockage in the blood vessel. In addition, thrombolysis alone -- even when successful -- cannot treat tissue that has already been damaged by compromised blood circulation. So, further treatment may be needed to address the underlying causes of the blood clot and repair damaged tissues and organs.