Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns... As per your complain a root canal treated tooth if treatment is done successfully and there is no symptoms like pain in tooth and swelling in gums or over jaw then there is no chance of any other problem and seizure is not caused by it.. In a very rare chances it there is a long standing case of infection in tooth there can be septicemia and it can reach brain and cause VENOUS SINUS THROMBOSIS and can lead to obstruction in blood flow and can lead to seizures but it is very rare case and not evident in case of a root canal treated tooth it there are no other symptoms.. You should take him to a Neurophysician and get him evaluated and get a CT SCAN done to get ruled out for exact cause of the illness and get treated accordingly.. As far as your case is concerned dental infection can lead to BACTERIAL ENDOCARDITIS in a few cases which is a fatal illness but is also a rare condition but once it has happened it has to be treated and cannot simply get improved by getting tooth extracted. Palpitations can occur due to side effect of local anaesthetic or any medication but as the medicine is stopped it gradually improves and it is also not due to root canal treatment.. So in your case also root canal treatment is not the direct cause of problem, so if you also experience such symptoms again better consult a Cardiologist and get evaluated.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora