Catheter ablation, is a treatment that aims to control or correct certain types of abnormally fast heart rhythms. Most episodes of paroxysmal AF are triggered by an extra heartbeat, or ectopic, from just inside one of the pulmonary veins, which carry oxygenated blood from the lungs back to the heart's chamber called the left atrium. Cells just inside the entrances to these veins fire to cause an extra heart beat which triggers AF. A technique called Pulmonary Vein Isolation, or PVI for short, is a commonly performed procedure. It involves the process of creating an electrical barrier around the entrance to the pulmonary veins. If this barrier exists, ectopics from cells inside the veins cannot conduct to the left atrium to cause an episode of AF. The procedure is often carried out under general anaesthesia via small incisions made at the top of the leg . Catheters and other instruments can then be passed through these tubes directly up to the heart via the veins inside the body. An x-ray camera guides this process.