Are there serious risks with cardiac ablation for atrial fibrillation?

There are potentially serious risks related to a.fib ablations, though overall the risks are very low.

At most centers, there is a 1-2% risk of a bleeding complication in the groin where the catheters are inserted. There is roughly a 0.1-0.2% of a severe enough bleeding problem that a vascular surgeon needs to make a small incision in the groin to find the source of continued bleeding and stitch it up. 

At most centers, there is a 1-2% risk of having one of the catheters in the heart perforate an outer wall of heart causing bleeding into the tissue sac the heart sits in. This is called tamponade and can be immediately life-threatening if it is not immediately recognized. Fortunately, most high-volume ablation centers have safe-guards in place to detect this sort of bleeding and can respond to it immediately. The ablation procedure must be stopped immediately (possibly resulting in an incomplete ablation) and a drainage tube is inserted under the breastbone to drain the blood out of the sac around the heart. The site of bleeding usually will seal itself up, though there is about a 0.1% chance of needing urgent open heart surgery to find the source of continued bleeding and stitch it up.

There is a risk of stroke associate with a.fib ablations, though this risk is usually not significantly different than the risk of stroke each patient has on a daily basis according to their other medical problems.

Depending on the type of ablation performed, there are specific risks related to different energy sources. For radiofrequency ablation, there is an extremely remote chance (10 or so cases reported worldwide) of developing an atrio-esophageal fistula—a small tunnel between the atrium and esophagus—that can be catastrophic. Most centers have changed their ablation strategies and safeguards to try to minimize the risk of this complication. There is a risk of narrowing of the pulmonary veins (where the bulk of ablation is performed), though newer technologies and ablation strategies have significantly minimized this risk. There is a risk of temporary paralysis of the nerve that makes the right diaphragm muscle move though, again, safeguards have been generally adopted to minimize this risk.

Overall, ablation for atrial fibrillation is a safe and effective procedure that offers the only chance for cure of a chronic debilitating disease. There are serious risks associated with ablation, however the overall chance of a complication is very low.