Author + information
- Brian Whisenant, MD∗ ( and )
- James Orford, MD
- ↵∗Reprint requests and correspondence:
Dr. Brian Whisenant, Intermountain Heart Institute, Intermountain Medical Center, 5121 South Cottonwood Street, Murray, Utah 84107.
The PROTECT AF (Percutaneous closure of the left atrial appendage versus warfarin therapy for prevention of stroke in patients with atrial fibrillation) trial demonstrated tremendous clinical results despite complications and procedure failures associated with the initial learning phase of the Watchman device (Boston Scientific, St. Paul, Minnesota). With 2.3 years of follow up, the primary endpoint intention to treat composite rate of all stroke, systemic embolism, and cardiovascular or unexplained death was 3.0 events per 100 patient-years with device and 4.3 events per 100 patient-years with warfarin (relative risk: 0.71). The true efficacy and potential of left atrial appendage (LAA) closure were demonstrated by the per-protocol analysis that restricted the device group to patients with successful implants who stopped taking warfarin after the specified period and patients in the control group who sustained warfarin therapy. Fewer patients in the group randomized to receive the Watchman device experienced primary efficacy events than in the control group (2.3% per year vs. 4.1% per year; probability of superiority 0.96) (1). The follow-up PREVAIL (Prospective Randomized Evaluation of the WATCHMAN LAA Closure Device in Patients with Atrial Fibrillation versus Long Term Warfarin Therapy) trial was recognized for its improved procedural outcomes. Clinical success defined as device deployment and release was achieved in 95% of enrolled subjects, whereas 96% were free of adverse events defined as a composite of cardiac perforation, pericardial effusion with tamponade, ischemic stroke, device embolization, and other vascular complications requiring intervention (2). The totality of Watchman efficacy and safety data supported Food and Drug Administration approval of the Watchman Occluder as an alternative to warfarin for patients with reasons to avoid chronic oral anticoagulants. Although the published Watchman experience to date is outstanding, we are in the infancy of LAA closure therapy with numerous opportunities to optimize LAA closure to deliver the safest and most effective stroke prevention possible.
In this issue of JACC: Cardiovascular Interventions, Wang et al. (3) performed their institution’s initial 53 Watchman procedures with meticulous computed tomography (CT)–guided case planning including 3-dimensional (3D) printing. As Watchman represents the only viable option for many high stroke risk, high bleeding risk patients with atrial fibrillation, it is noteworthy that all screened patients proceeded to successful device deployment and LAA closure without significant procedural complications. The maximal CT-measured LAA diameter was 2.7 ± 2.2 mm larger than the maximal 2-dimensional (2D) transesophageal echocardiography (TEE)-measured LAA diameter. Several patients could not have been treated according to the Watchman instructions for use (IFU) given 2D TEE measured ostial diameters or appendage depths, but were treated within IFU parameters according to CT measurements. They required a modest average of 1.245 devices per patient without changing device size and logically hypothesized that fewer device recaptures ultimately translate to fewer pericardial effusions. They concluded that 3D CT–guided case planning provided a high level of device selection accuracy, simplified their implantation process, and is the preferred method of sizing and procedural planning.
The commitment to delivering the best possible procedure to each patient is admirable and may have contributed to not only procedural safety but also long-term stroke reduction. When the CT-derived ostium was ambiguous, a Watchman device was implanted ex vivo in the patient’s 3D printed LAA to test device sizes and delivery catheters. The authors anticipated intraprocedural c-arm angles to visualize the profile of a coaxial delivered device, which may have limited procedural contrast and optimized deployment. CT imaging and 3D printing may also predict the optimal location for transseptal puncture in each patient. Such planning may lead to improved closure efficacy, which in turn may translate to diminished long-term strokes. The four observed peri-Watchman leaks in this series were each <4.5 mm in width, which would be adjudicated as closed according to the PROTECT AF trial definition of no gap >3 ± 2 mm. An initial PROTECT AF trial analysis suggests that such residual gaps do not translate to an increased risk of stroke. One thrombus was observed 1 month following device implantation on CT.
The authors described a sophisticated protocol that included retrospectively gated computed tomographic angiography acquisition, 3D reconstruction software, manual segmentation, and 3D printing by industrial designers, which may not be practical for most centers performing routine clinical LAA closures. However, with increased utilization of CT for LAA evaluation, acquisition and analysis protocols will become increasingly standardized and useful, likely supported by commercial vendors.
In addition to pre-procedural planning, there is much yet to be learned from CT imaging of the left atrial appendage. Previous studies have demonstrated that CT-defined increased LAA volume is associated with an increased risk of stroke (4) whereas chicken wing morphology is associated with a decreased risk of stroke (5). CT may supplement clinical scores such as CHA2DS2-Vasc to guide stroke prevention therapies. Some anatomies such as those with trabeculations of the proximal limbus may be associated with an increased risk of stroke despite successful Watchman closure. The optimal post-LAA closure pharma regimen remains unknown and may be influenced by CT-defined anatomy. As devices in addition to Watchman become available, CT may define anatomies best addressed with specific devices.
In addition to expense and effort, CT imaging of the LAA is associated with nephrotoxic risks of intravenous contrast and radiation exposure. Experienced Watchman implanters have learned that modest oversizing beyond that suggested by 2D TEE often provides optimal closure. Deployment of the self-expanding Watchman device is imprecise but forgiving which may somewhat dilute the benefit of precise procedure planning. The authors concluded that comprehensive CT-based case planning not only is feasible but also may enhance procedural safety and efficiency analogous to the impact delivered in transcatheter aortic valve interventions. However, unlike transcatheter aortic valve replacement where CT-derived annulus sizing has become the standard of care for most patients, CT must be considered a supplemental option in addition to transesophageal evaluation of the LAA. Decisions regarding incorporating CT into the pre-procedure evaluation will depend on both institutional as well as patient-specific factors. Although 2D and 3D TEE may be preferable for patients with compromised renal function or centers with unique TEE expertise, centers with CT and 3D printing expertise may routinely incorporate CT into their pre-Watchman evaluation. In the rare case when Watchman deployment proves difficult, returning at a later date after additional CT evaluation may also be an option. Although pre-procedure evaluations and workflows may differ, all centers should share a common vision of successful LAA closure with minimal complications for all deserving patients.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Whisenant has received payment from Johnson & Johnson for consultation and Coherex equity; and has received honoraria from and served as a proctor for Boston Scientific. Dr. Orford has reported that he has no relationships relevant to the contents of this paper to disclose.
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