Stroke and Thromboembolism Trials
Reductions in stroke and thromboembolism remain the most important goals of AF treatment. It is unclear, however, if elimination of or reductions in AF will necessarily reduce the associated risk of stroke, and whether such outcomes exceed those possible with NOAC agents. Although an increased risk of stroke appears to be associated with brief episodes of AF detected by implanted cardiac devices, multiple large randomized trials have demonstrated that there might be no temporal relationship between AF episodes and AF thromboembolic events. This possibility has cast significant doubt regarding the direct causal role that AF plays in stroke. On the other hand, some cohort studies of AF ablation have reported a lower risk of stroke postablation compared with matched, nonablated AF populations. The impact of AF ablation on stroke and thromboembolism is an important topic of future study and will likely require a combination of very large studies with long durations of follow-up akin to CABANA and EAST. The OCEAN study is currently getting started, and will examine the optimal strategy for ongoing antithrombotic therapy 1 year after successful ablation in a moderate-risk profile population with a primary endpoint of overt and covert stroke. It is important to stress that until the results of these trials are known, the current recommendations are to continue anticoagulation indefinitely in patients with CHA2DS2-VASc ≥2, regardless of the success of the ablation procedure.
Periprocedural stroke reduction is an important topic that is actively being studied, with various strategies of anticoagulation, particularly continuous administration of VKA and non-VKA oral anticoagulants through the ablation procedure.834, 841,842 In addition, concomitant LAA occlusion is being tested. In percutaneous procedures, there are few if any studies powered for stroke alone; most primarily evaluate AF recurrence.
Finally, multiple studies have demonstrated small ACE on MR brain imaging after ablation.724,728,1207 The clinical significance of such ACE lesions is not known, and many will resolve to the point of being undetectable after weeks or months. The impact on cognitive function, if any, is not clear. At this point, there are no mandates for performing periprocedural brain imaging for novel technologies to evaluate the incidence of silent cerebral embolism, in large part because of its unknown clinical significance and the cost and burden of MRI on patients. However, further evaluation of the significance of such findings remains an important area of study.
Screening substudies could be reasonable for high-risk devices and should be combined with clinical neurological and cognitive assessments. These silent cerebral emboli are to be distinguished from covert embolic strokes secondary to long-term AF, which have been linked with long-term cognitive decline, and are much larger than the silent emboli seen peri-procedurally.1385,1386,1387,1388