What Are the Most Current Data on Left Atrial Appendage (LAA) Closure?
The LAA is an embryonic remnant of the original left atrium, and stagnant blood flow within it can provoke formation of clots, which in nonvalvular atrial fibrillation (NVAF) can dislodge from the heart and cause stroke—not just in the brain, but in any organ. Years ago, researchers realized that closing off the LAA—like corking a wine bottle—may prevent these clots from exiting the heart in the first place. Thus, the endovascular Watchman LAA (Boston Scientific Corporation) device was born. This self-expanding umbrella-shaped filter is inserted into the left atrium via trans-septal puncture, then permanently implanted within the LAA ostium. Periprocedurally, anticoagulation is given for 45 days, while an endothelial layer grows over the device. Afterward, the anticoagulant therapy is typically replaced with an antiplatelet therapy.
In two randomized studies, a pivotal clinical trial (Watchman Left Atrial Appendage System for Embolic Protection in Patients With Atrial Fibrillation [PROTECT AF]) and a second confirmatory trial (Watchman LAA Closure Device in Patients With Atrial Fibrillation Versus Long-Term Warfarin Therapy [PREVAIL]), Watchman patients had a statistically significant 80% reduction in hemorrhagic strokes versus warfarin (relative risk [RR], 0.2; confidence interval [CI], 0.07–0.56), primarily because patients no longer required lifelong anticoagulant therapy for stroke prevention from the NVAF. With 5 years of follow-up in both studies, the primary composite endpoint of stroke, cardiovascular death, and systemic embolism occurred in 2.8 per 100 patient-years in the Watchman group and 3.4 per 100 patient-years in the warfarin group (RR 0.82, CI 0.58–1.17), proving noninferiority of the device. The Food and Drug Administration (FDA) requested more safety/efficacy data based on procedure complications seen very early in the PROTECT AF trial, so the Continued Access Protocol and the PREVAIL trial were initiated. Both showed better procedural safety results than PROTECT AF, and PREVAIL mandated a percentage of new operators to test the efficacy of the implanter training program. Postmarketing real-world data from the United States and Europe showed successful deployment rates (> 95%) and few procedural complications (such as pericardial effusion/tamponade, device embolization, procedural stroke, and death) when compared to the trials or compared to ablation. Finally, Watchman also had a significant reduction in all-cause mortality (27%; P = .04) and disabling strokes (55%; P = .03), which is what matters most to me as a vascular (stroke) neurologist.
Which Patients Should be Considered for LAA Closure?
Watchman received FDA approval for stroke prevention from NVAF in March 2015. The Centers for Medicare & Medicaid Services (CMS) covers Watchman for patients with NVAF and a relatively high embolic risk score (CHADS2 ≥ 2 or CHA2DS2DS2-VASc ≥ 3) suitable for short-term warfarin use, in whom “there is an appropriate rationale to seek a nonpharmacologic alternative to oral anticoagulants.” However, the art of medicine is deciding which patient in your neurologist’s office is best suited for the intervention. For example, I have a young patient—a fighter pilot—who had a small stroke, and recovered well, but needed daily anticoagulation for NVAF, which precluded him from flying in combat. Thus, he was relegated to a desk job at the military base. When I told him about the possibility of Watchman, which could allow him to avoid long-term anticoagulation, he lit up with the possibility of returning to his jet. Or, for another patient, a woman in her 90s (who is “Florida active”—driving, playing tennis and golf, swimming, socializing) who bruises easily on anticoagulation and has a few dots on the gradient echo sequence of her brain MRI, suggesting microhemorrhages: why not consider Watchman for her?
What Is the Role of the Neurologist Before and After Watchman Implantation?
The neurologist plays a critical role for patients looking into Watchman, particularly for those who have had a stroke. First, the neurologist can individualize the safety and efficacy of the device compared with oral anticoagulation for each patient using CHADS-VASc and HASBLED scoring systems, and determine if an ischemic stroke was likely from NVAF or from another etiology (such as ipsilateral carotid disease, craniocervical arterial dissection, or intracranial atherosclerosis). Second, the neurologist can help answer the question as to when a patient can resume anticoagulation for NVAF after a stroke, which depends on stroke size, cause, location of brain territory affected, and overall functional status. Third, if there is a hint of dementia, the gradient echo sequence of brain MRI must be scrutinized. Several microhemorrhages could indicate a diagnosis of cerebral amyloid angiopathy, in which case doctors must be wary about anticoagulation due to the risk of intracranial hemorrhage. Finally, CMS approval mandates a formal shared decision-making interaction with an independent noninterventional physician using an evidence-based decision tool, and neurologists are perfectly positioned to assist their patients (and cardiology colleagues) in this endeavor. Outcomes are best when a cohesive, multidisciplinary team of medical professionals are all in alignment.
How Will the Data Continue to Evolve for LAA Closure?
LAA closure is exciting and revolutionary in NVAF and stroke management. In the near future, short-term use of direct oral anticoagulants periprocedurally may be offered at some centers, and preliminary data suggest results similar to warfarin, but trials are ongoing. Also, for patients who are unsuitable for anticoagulation to reduce stroke risk from NVAF, the Assessment of the Watchman Device in Patients Unsuitable for Oral Anticoagulation (ASAP-TOO) trial is underway in the United States, using Watchman either with antiplatelet therapy or without any blood thinner. These practical issues are addressing the real-world needs of the patient with NVAF and stroke.
David Z. Rose, MD
University of South Florida
Morsani College of Medicine
Medical Director, Neuro-ICU
Tampa General Hospital