The Watchman device (Boston Scientific Corporation) is changing the way we practice stroke prevention or treatment of atrial fibrillation. For the first time, a fully percutaneous intracardiac device has been compared against oral anticoagulation in a randomized controlled trial with a good outcome. How do we select patients? How do we integrate this technology into our practice? This article will endeavor to answer those questions.

KEY FEATURES OF THE DEVICE

The Watchman device consists of a nitinol frame and a fabric cap. The nitinol structure comes in five available sizes: 21, 24, 27, 30, and 33 mm in diameter. There are 10 fixation anchors around the device perimeter that are used to fix the device into the left atrial appendage (LAA) tissue. The nitinol frame is covered with a polyethylene terephthalate fabric, which acts as a 160-μm filter that prevents emboli from passing through the device (Figure 1).

The sheath comes in both double and single anterior curves. The sheath has a 14-F outer diameter (4.7 mm) and a 12-F inner diameter, and it comes in a 75-cm working length. One unique feature of this device is that one sheath is used for all five device sizes. The delivery system consists of a deployment knob connected to a core wire that travels through a hemostasis valve into the sheath (Figure 2).

When the device is loaded into the sheath, the markers on the sheath can give a clue as to where the device will land when deployed. The device is loaded to the most distal radiopaque marker band; the three successively proximal marker bands correspond approximately to 21-, 27-, and 33-mm constrained devices, and the spaces between correspond approximately to 24- and 30-mm constrained devices (Figure 3).

When the device is implanted, it should be checked by four criteria prior to release. The first of these is the position, to make sure that the device does not protrude proximally too far (this should be confirmed in multiple transesophageal views on echocardiography). The second is the anchor pull test, in which the operator gently retracts the deployment knob and releases, observing the device returning to its original position without shift on both fluoroscopy and echocardiography. This confirms that the fixation anchors are engaged. Third is size compression, in which the device is examined for a decrease in measured diameter to between 80% and 92% of the original diameter. Finally, the last test is an evaluation for seal by assessing peridevice leak via atrial angiography and also in multiple echocardiographic views (eg, 0°, 45°, 90°, and 135°). Together, the position, anchor, size, and seal tests make the mnemonic PASS.

PATIENT POPULATION AND SELECTION

To understand the possible patient population and selection for the United States, one should understand the patients studied in both the PROTECT-AF1-3 and the PREVAIL4 trials. The PROTECT-AF trial was a prospective, randomized (2:1), noninferiority trial of LAA closure versus warfarin in nonvalvular atrial fibrillation patients for prevention of stroke. This was followed by a combined safety analysis of PROTECT-AF and the CAP registry, which showed a decrease in procedural complications with experience.2 The PROTECT-AF trial included patients with paroxysmal, persistent, or permanent nonvalvular atrial fibrillation, who were all eligible for long-term warfarin therapy. These patients had a CHADS2 score ≥ 1. Exclusion criteria were patients who were contraindicated for aspirin or clopidogrel and had New York Heart Association class IV heart failure, an implanted mechanical valve, an atrial septal or patent foramen ovale device, platelets < 100,000/μL or hemoglobin < 10 g/dL, and patients with a left ventricular ejection fraction of < 30%. PREVAIL had slightly more stringent inclusion criteria, including a CHADS2 score > 2 or CHADS2 score = 1 if the patient fulfilled certain criteria (female, aged older than 75 years, baseline left ventricular ejection fraction > 30 and < 35%, 65–74 years of age with diabetes or coronary artery disease, and 65 years of age or older with documented congestive heart failure). Other probable exclusion criteria are patients with a known other source of emboli (left ventricular thrombus or mobile atheromatous aortic plaque) or a short life expectancy.

Of note, the study inclusion criteria of PROTECT-AF is different from patients included in European guidelines, in which “interventional, percutaneous LAA closure may be considered in patients with a high stroke risk and contraindications for long-term oral anticoagulation,” receiving a IIb rating (level of evidence, B).5 This guideline was based on the ASAP trial, in which patients who were not candidates for oral anticoagulation safely received the Watchman device with only aspirin and clopidogrel as postprocedural therapy.6

In the United States, there was a positive US Food and Drug Administration (FDA) panel vote of 13-1 in December 2013. Approval is expected soon, with labeling still to be defined. At this point, it is too early to know what the planned patient population and selection will be in the United States after approval. One can presume that it will be for nonvalvular atrial fibrillation patients with an indication for warfarin but with a reason to seek an alternative treatment to reduce the risk of thromboembolism from the LAA. Because the patient must also qualify based on certain anatomical size limitations of the procedure and device, the patient must also be able to tolerate transesophageal echocardiography (TEE), which is also important to rule out LAA thrombus or other known sources of emboli.

IMPACT ON PRACTICE

The impact on practice depends on the indication for the device, which is dependent on the FDA indication and CMS coverage decisions. There are more than 5 million people with atrial fibrillation in the United States, and studies have estimated that the overall prevalence is 1% to 2% of the general population. The prevalence of atrial fibrillation is age dependent, with prevalence rates of < 0.5% to 1%, 1% to 4%, and 6% to 15% for ages 50, 65, and 80 years, respectively. Even then, this may be an underestimate, with underdiagnosis due to intermittent atrial fibrillation or intermittently symptomatic atrial fibrillation, especially when estimates are based on studies utilizing electrocardiography at the time of symptoms.7

Atrial fibrillation is associated with a three- to five-fold increased risk of stroke and accounts for 20% of all strokes.8 In addition, strokes associated with atrial fibrillation are more recurrent and are often more severe, which utilizes more resources, ends with more disability, and leads to higher mortality compared to the 80% of strokes that occur without atrial fibrillation.9-11

What is the overall impact of atrial fibrillation on the United States? One study published in 2006 quotes 350,000 hospitalizations, 5 million office visits, 276,000 emergency department visits, and 234,000 urgent care visits per year due to atrial fibrillation. Total annual costs were estimated at $6.65 billion, with $2.93 billion (44%) for primary discharge diagnosis, $1.95 billion (29%) for incremental inpatient hospitalization costs as a comorbid diagnosis, $1.53 billion (23%) for outpatient treatment of atrial fibrillation, and $235 million (4%) for prescription drugs.12 A cost evaluation in the province of Ontario, Canada, was recently published. Although the costs are based on Canadian dollars and care, the results were significantly in favor of LAA occlusion, with higher quality-adjusted life years and lower discounted lifetime costs compared to warfarin or dabigatran.13

What is the impact of LAA closure on practice? This is tough to say because this will depend on a few factors. The first is the need to isolate the number of nonvalvular atrial fibrillation patients without another reason to be on oral anticoagulation therapy (eg, a patient with a mechanical valve, recurrent pulmonary embolism, or hypercoagulable disorder requiring lifelong warfarin). The second factor is whether this will be listed as a first-line therapy in comparison to oral anticoagulation or a second-line therapy to oral anticoagulation. Although European numbers may not be used as a direct comparison, European guidelines5 gave IIb approval to patients who were not able to undergo anticoagulation. In contrast, the United States is seeking approval for patients who are candidates for anticoagulation. The third factor is how widespread LAA closure will be; this depends on how many interventional cardiologists, electrophysiologists, and hospital systems are capable of implementing this procedure. A fourth factor is the need for adequate reimbursement, which is discussed in the following section.

REGULATION AND REIMBURSEMENT

The United States regulations and reimbursement codes are still to be determined for the Watchman device; however, Boston Scientific may likely push for certain qualifications for a site to be ideally situated to start a Watchman program. This section primarily includes recommendations from Boston Scientific, but it is likely that the FDA and CMS official requirements may vary from these.

The site will likely need a dedicated interventional/ heart team to support Watchman procedures. The personnel will include a coordinator, multispecialty implanting physician team (collaboration between electrophysiology and interventional cardiology), dedicated echocardiographer who will attend formal implantation training, anesthesiology support, cardiac surgery backup, and consistent nurse/tech support with scrubbing in on all procedures. The implanting physicians should include at least one who has performed a significant number of interventional cardiac procedures requiring a transseptal puncture. The team would benefit from having experience and teamwork in performing other complex procedures, such as transcatheter aortic valve replacement, mitral valve interventions, and/or ablation procedures. There should also be adequate space to perform LAA closure in the cath lab/electrophysiology lab.

There is a significant learning curve that accompanies LAA closure. Therefore, operators and teams should be capable of handling complications such as hematoma/ vascular injury, pericardial effusion/tamponade, and device embolization. Some complications happen or are recognized after the patient has left the lab; the receiving hospital unit should have the capacity to recognize and react to such issues emergently.

From a reimbursement perspective, the Watchman LAA closure system has an associated code and payment. However, coverage will need to be defined when the device becomes commercially available.

DRAWBACKS AND CHALLENGES

One of the drawbacks to all LAA closure devices stems from issues related to the operator learning curve, including complication prevention and management. Possible complications are vascular access injury, transseptal puncture issues, air embolism (leading to stroke or myocardial infarction), device embolization, and also pericardial effusion/tamponade. Careful vigilance is needed to prevent these complications; it is important that the staff is ready and able to handle complications before they occur.

The Watchman device also requires a significant anatomical depth prior to implantation. For small lobes or large shallow LAAs, the Watchman device may not be a feasible option.

Other challenges include the appropriate follow-up period after implantation of the device. Current practice, as per the PROTECT-AF trial, is to continue anticoagulation with warfarin after the procedure until a 45-day follow-up TEE is performed. If there is no thrombus and seal is present (residual peridevice flow < 5 mm in width on TEE), warfarin is discontinued, and aspirin (81–325 mg) and clopidogrel (75 mg) are given for a total of 6 months, after which, aspirin is continued indefinitely. If a leak or thrombus is seen, warfarin is continued. It is unclear as to how long warfarin should be continued in those circumstances when thrombus or a leak occurs. A substudy of the PROTECT-AF trial showed that 32% of patients had some peridevice flow at 12 months; however, this was not associated with a higher risk of thromboembolism (although there was a low overall event rate).14

FUTURE DIRECTIONS

The next-generation Watchman 5 device (Figure 4) has significant changes compared to the current Watchman device. There is a closed distal end, an expanded LAA treatment range, and enhanced sealing. The device is also capable of full recapture and redeployment, as with the previous generation.

There are also other areas for expansion of United States indications. The device has been tested in patients who are not candidates for anticoagulation in the ASAP trial,6 which showed that LAA closure with the Watchman device can be safely performed without a warfarin transition. For patients who cannot tolerate TEE, LAA closure procedures have been performed with intracardiac echocardiography.15,16

Other areas of interest are in imaging for LAA closure. As previously mentioned, intracardiac echocardiography is being used in some centers for periprocedural imaging; the LAA procedure has been performed without general anesthesia.16 CT imaging has also been used for thrombus exclusion and appendage sizing.17,18

Further clinical studies are currently being conducted. An international registry called the Registry on WATCHMAN Outcomes in Real-Life Utilization (EWOLUTION), is one such study collecting data.19 This 45-center study is designed as an observational prospective cohort study that will follow patients for up to 2 years to describe procedural safety and long-term efficacy. The estimated enrollment is 1,000 patients. In addition, it is highly likely that the FDA will require a postapproval study as a condition of approval.

CONCLUSION

The burden of atrial fibrillation is significant in the United States population, especially due to the risk of overall and severe stroke. The Watchman LAA closure device is a proven device that reduces the occurrence of stroke in patients with nonvalvular atrial fibrillation. Approval is expected in 2014, with labeling still to be confirmed. Sites in the United States will most likely need to have a team that cooperatively recruits, discusses, treats, and follows patients together to be successful. Involvement in a postapproval study may also be required. This information will be very important for inclusion and advancement in the United States society guidelines for atrial fibrillation. Recently, the FDA requested an additional advisory panel review of the WATCHMAN trial data. At the time of this writing, the reasons for the third panel meeting are not clear. While FDA approval had been anticipated, it is clear that any further clarity about the status of US approval and commercialization will depend on the upcoming FDA review.

Sameer Gafoor, MD, is with the CardioVascular Center Frankfurt in Frankfurt, Germany. He stated that he has no financial interests related to this article.

Jennifer Franke, MD, is with the CardioVascular Center Frankfurt in Frankfurt, and the University of Heidelberg in Heidelberg, Germany. She stated that she has no financial interests related to this article.

Markus Reinartz, MD, is with the CardioVascular Center Frankfurt in Frankfurt, Germany. He stated that he has no financial interests related to this article.

Stefan Bertog, MD, is with the CardioVascular Center Frankfurt in Frankfurt, and the Minnesota Veterans Affairs Medical Center in Minneapolis, Minnesota. He stated that he has no financial interests related to this article.

Laura Vaskelyte, MD, is with the CardioVascular Center Frankfurt in Frankfurt, Germany. She stated that she has no financial interests related to this article.

Ilona Hofmann, MD, is with the CardioVascular Center Frankfurt in Frankfurt, Germany. She stated that she has no financial interests related to this article.

Prof. Horst Sievert, MD, is with the CardioVascular Center Frankfurt in Frankfurt, Germany. He has disclosed that he has ownership interest in or has received consulting fees, travel expenses, or study honorariums from the following companies: Abbott, Access Closure, AGA, Angiomed, Arstasis, Atritech, Atrium, Avinger, Bard, Boston Scientific, Bridgepoint, Cardiac Dimensions, CardioKinetix, CardioMEMS, Coherex, Contego, CSI, EndoCross, EndoTex, Epitek, Evalve, ev3, FlowCardia, Gore, Guidant, Guided Delivery Systems, Inc., InSeal Medical, Lumen Biomedical, HLT, Kensey Nash, Kyoto Medical, Lifetech, Lutonix, Medinol, Medtronic, NDC, NMT, OAS, Occlutech, Osprey, Ovalis, Pathway, PendraCare, Percardia, pfm Medical, Rox Medical, Sadra, SJM, Sorin, Spectranetics, SquareOne, Trireme, TriVascular, Velocimed, and Veryan. Prof. Sievert may be reached at +49 69 46031344; info@cvcfrankfurt.de.

  1. Holmes DR, Reddy VY, Turi ZG, et al. Percutaneous closure of the left atrial appendage versus warfarin therapy for prevention of stroke in patients with atrial fibrillation: a randomised non-inferiority trial. Lancet. 2009;374:534-542.
  2. Reddy VY, Holmes D, Doshi SK, et al. Safety of percutaneous left atrial appendage closure: results from the Watchman Left Atrial Appendage System for Embolic Protection in Patients With AF (PROTECT AF) clinical trial and the Continued Access registry. Circulation. 2011;123:417-424.
  3. Reddy VY, Doshi SK, Sievert H, et al. Percutaneous left atrial appendage closure for stroke prophylaxis in patients with atrial fibrillation: 2.3-year follow-up of the PROTECT AF (Watchman Left Atrial Appendage System for Embolic Protection in Patients With Atrial Fibrillation) trial. Circulation. 2013;127:720-729.
  4. Holmes DR, Kar S, Price MJ, et al. Prospective randomized evaluation of the Watchman left atrial appendage closure device in patients with atrial fibrillation versus long-term warfarin therapy. J Am Coll Cardiol. 2014; DOI:10.1016/j.jacc.2014.04.029.
  5. Camm AJ, Lip GY, De Caterina R, et al. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation: an update of the 2010 ESC Guidelines for the management of atrial fibrillation. Developed with the special contribution of the European Heart Rhythm Association. Eur Heart J. 2012;33:2719-2747.
  6. Reddy VY, Mobius-Winkler S, Miller MA, et al. Left atrial appendage closure with the Watchman device in patients with a contraindication for oral anticoagulation: the ASAP study (ASA Plavix Feasibility Study With Watchman Left Atrial Appendage Closure Technology). J Am Coll Cardiol. 2013;61:2551-2556.
  7. Andrade J, Khairy P, Dobrev D, Nattel S. The clinical profile and pathophysiology of atrial fibrillation: relationships among clinical features, epidemiology, and mechanisms. Circ Res. 2014;114:1453-1468.
  8. Cotter PE, Martin PJ, Ring L, et al. Incidence of atrial fibrillation detected by implantable loop recorders in unexplained stroke. Neurology. 2013;80:1546-1550.
  9. Winter Y, Wolfram C, Schaeg M, et al. Evaluation of costs and outcome in cardioembolic stroke or TIA. J Neurol. 2009;256:954-963.
  10. Bruggenjurgen B, Rossnagel K, Roll S, et al. The impact of atrial fibrillation on the cost of stroke: the Berlin acute stroke study. Value Health. 2007;10:137-143.
  11. Petty GW, Brown RD Jr, Whisnant JP, et al. Ischemic stroke subtypes: a population-based study of functional outcome, survival, and recurrence. Stroke. 2000;31:1062-1068.
  12. Coyne KS, Paramore C, Grandy S, et al. Assessing the direct costs of treating nonvalvular atrial fibrillation in the United States. Value Health. 2006;9:348-356.
  13. Singh SM, Micieli A, Wijeysundera HC. Economic evaluation of percutaneous left atrial appendage occlusion, dabigatran, and warfarin for stroke prevention in patients with nonvalvular atrial fibrillation. Circulation. 2013;127:2414-2423.
  14. Viles-Gonzalez JF, Kar S, Douglas P, et al. The clinical impact of incomplete left atrial appendage closure with the Watchman Device in patients with atrial fibrillation: a PROTECT AF (Percutaneous Closure of the Left Atrial Appendage Versus Warfarin Therapy for Prevention of Stroke in Patients With Atrial Fibrillation) substudy. J Am Coll Cardiol. 2012;59:923-929.
  15. Ho IC, Neuzil P, Mraz T, et al. Use of intracardiac echocardiography to guide implantation of a left atrial appendage occlusion device (PLAATO). Heart Rhythm. 2007;4:567-571.
  16. Ronco F, Pascotto A, Barbierato M, Grassi G. Percutaneous left atrial appendage closure in awake non intubated patient: multimodality intraprocedural imaging. Cardiovasc Revasc Med. 2012;13:360-361.
  17. Nasis A, Mottram PM, Cameron JD, Seneviratne SK. Current and evolving clinical applications of multidetector cardiac CT in assessment of structural heart disease. Radiology. 2013;267:11-25.
  18. Wu X, Wang C, Zhang C, et al. Computed tomography for detecting left atrial thrombus: a meta-analysis. Arch Med Sci. 2012;8:943-951.
  19. ClinicalTrials.gov website. Registry on WATCHMAN Outcomes in Real-Life Utilization (EWOLUTION). http:// www.clinicaltrials.gov/ct2/show/NCT01972282. Accessed May 28, 2014.