When methods of cardioversion and medications are not effective at treating atrial fibrillation, catheter ablation is usually the next method used. Catheter ablation is a minimally invasive procedure used to destroy the sections of tissue in the patient's heart causing atrial fibrillation. During a catheter ablation procedure, a catheter or long thin tube is inserted into a large vessel in the patient's groin and is threaded up to their heart. The places in the heart causing the inappropriate conduction of electricity are then identified and located. The surgeon then uses the catheter to apply cryotherapy, radiofrequency, or heat to destroy these tissues. This process causes scar tissue to form as a replacement for the tissue that was destroyed. Scar tissue is stiffer and denser than normal tissue, making it unable to conduct electricity. This scar tissue helps redirect the electrical impulses in the patient's heart back to a healthy and normal path and pattern.