Several periprocedural steps are routinely taken during catheter ablation procedures for atrial fibrillation (AF) to minimize the risk of embolic stroke, and as a result, the current rate of stroke related to the procedure is quite low. However, there is increasing evidence that the risk of subtle cognitive decline is more common than the risk of stroke related to the procedure. There is also evidence of hyperintense lesions on post-procedural magnetic resonance imaging of the brain, likely from microbubbles and particulate matter generated during delivery of energy to the left atrium, that might be the cause of cognitive decline.
Medi et al from Dr. Kalman’s lab in Melbourne, Australia recently published an interesting study related to cognitive function after radiofrequency (RF) ablation for AF.1 They studied four groups of patients: 60 patients with paroxysmal AF (PAF) who underwent RF ablation, 30 patients with persistent AF (PeAF) who underwent ablation, 20 patients with paroxysmal supraventricular tachycardia (SVT) treated with ablation (left sided in 7 patients), and 30 control patients with AF who did not undergo ablation. Ablation for AF was done after interruption of warfarin and full-dose low-molecular-weight heparin bridging, and intraprocedural heparin administration targeting an activated clotting time over 300 seconds. Cognitive function was measured in these patients using 8 neuropsychological tests. Post-operative cognitive dysfunction (POCD) was defined as a significant failure on at least 2 tests or a more generalized subtle decline across all 8 tests. They found that POCD was present at 90 days in 13% of PAF patients, 20% of PeAF patients, 3% of SVT patients, and 0% of the patients who did not have an ablation. Left atrial access time was a univariate predictor of POCD.
The findings of this study are as puzzling as they are disturbing. It is disappointing to learn that an ablation procedure for atrial fibrillation, which is already associated with more complications and a lower success rate than most other procedures that are done in the electrophysiology laboratory, might also be associated with a significant risk of brain dysfunction. However, there are a lot of questions related to this data and it is important to keep the findings in perspective. An ablation procedure can dramatically improve a patient’s quality of life. For many patients, a small risk of a relatively subtle change in cognitive function after the procedure might be acceptable. We often recommend coronary artery bypass surgery to patients despite evidence that bypass can cause persistent cognitive dysfunction in a third of patients. It is also possible that elimination of the AF might prevent the cognitive decline that might occur as a consequence of the AF itself.
What can be done to prevent brain dysfunction after an ablation for AF? It seems unlikely that alternative periprocedural anticoagulation regimens are the key to prevention if the culprits are microbubbles and debris rather than device-related thrombi. Perhaps different ablation tools such as the cryoballoon would be less likely than RF to cause this problem. It is also possible that simply shortening procedure times, including the total anesthesia time and the left atrial “dwell” time, would make a difference. In this study, left atrial “dwell” time was associated with POCD. However, it does not appear that the relationship between the overall procedure time and POCD was analyzed. More information is clearly needed to better understand and prevent cognitive changes after ablation procedures for AF.
Bradley P. Knight, MD, FACC, FHRS
Editor-in-Chief, EP Lab Digest®
- Medi C, Evered L, Silbert B, et al. Subtle post-procedural cognitive dysfunction after atrial fibrillation ablation. J Am Coll Cardiol. 2013;62:531-539.