The limitations of oral anticoagulation to prevent stroke in patients with atrial fibrillation are well known. It is also apparent that nonpharmacological options focused on left atrial appendage occlusion have their own challenges. So there is clearly room for novel ideas and therapies in stroke prevention.
Rather than an approach of keeping any clots that may form in the left atrial appendage from embolizing to the brain, another strategy is to keep the clots from making their way to the brain. In a recent paper published online in the Journal of the American College of Cardiology, Dr. Vivek Reddy and colleagues published a very intriguing paper describing placement of filters in the bilateral carotid arteries to prevent stroke in patients with atrial fibrillation as part of the CAPTURE trial.1 They enrolled patients at high risk of stroke, half of which had had a previous embolic event, and who were also at high risk of bleeding, and inserted a percutaneous device designed to block clots directly into the carotid artery.
The filter is made of a fine nitinol wire that is described as being “super-elastic” with a diameter of 240 microns. It has anchoring loops distally and proximally, with a cone-shaped spiral in between the anchors to act as a filter that can catch clots greater than 1.4 mm in diameter. The cone-shaped spiral wire looks like a wire egg cup, with the apex of the cup pointed downward. Using ultrasound guidance, a 24-gauge needle is used to puncture the carotid artery above the common carotid artery, and then is directed downwards. Next, the filter is expelled through the needle and unfurled in the artery. The device was successfully placed in 92%, and patients were treated with dual antiplatelet therapy for 3 months afterwards.
The authors noted only minor complications in 20% of the patients that involved local hematomas that appear to have been easily managed. After 6 months and frequent periodic ultrasound imaging, they found clots trapped in the filters in four patients. These clots were treated with heparin and resolved in all patients. There were no strokes in the common carotid artery territory in these patients.
These are exciting first-in-man data related to a novel device that might prove to be helpful in preventing strokes in patients with atrial fibrillation. There are plans to perform a larger study in patients who are at high risk of stroke but do not have contraindications to anticoagulation. However, like most good studies, this study raises more questions than it answers. For example, is it clear that the clots that were found in the filters trapped embolic events rather than local thrombosis caused by the coils? The determination by the investigators that these were embolic events was based on the imaging features of the clot and the results of earlier bench and animal studies. However, the answer to this critical question remains uncertain. Another question is how this device would be used clinically. Would patients require frequent ultrasound imaging of the filter to identify trapped clots early, so they can be treated with heparin anticoagulation? This would not be practical. The authors suggest that the device could be implanted in patients who are candidates for anticoagulation so that embolic clots trapped in the filter would later dissolve. This then begs the question of whether additional nonpharmacological therapy is really needed in patients who can tolerate oral anticoagulation. Clearly, more information is needed before we can determine whether it is a good idea to place a small Slinky into patients’ carotid arteries.
Disclosure: Dr. Knight reports that he is a consultant, speaker, investigator, and offers fellowship support for Abbott, Baylis Medical, Biosense Webster, Inc., BIOTRONIK, Boston Scientific, Medtronic, and SentreHEART.
- Reddy VY, Neuzil P, de Potter T, et al. A Percutaneous Permanent Carotid Filter for Stroke Prevention in Atrial Fibrillation: The CAPTURE Trial. J Am Coll Cardiol. 2019 May 8. [Epub ahead of print] doi: https://doi.org/10.1016/j.jacc.2019.04.035.