Novel LAA Closure Device Shows Promise in Early Experience

SAN DIEGO, CA—A novel left atrial appendage (LAA) closure device could soon join others on the market, with data presented here at TCT 2018 showing rates of major adverse events and other safety outcomes that are comparable to those of similar commercially available devices.

Researchers led by Lluis Asmarats, MD (Laval University, Quebec City, Canada), say the findings are “encouraging” for this first initial outing with the Ultraseal (Cardia, Eagan, MN).

While the Watchman (Boston Scientific) and the Amplatzer Amulet (Abbott Vascular) are the two most widely used LAA closure devices (only the Watchman has been cleared for use in the United States), Asmarats and colleagues say unmet needs have fueled more innovation and device iterations. Among these are “the wide heterogeneity of LAA morphologies and sizes” that limit the suitability of existing devices in some patients.

The self-expanding Ultraseal is meant to address ongoing device improvement through a “bulb-and-sail design,” a fully articulating joint between the distal and proximal sections that allows multidirectional movement and adjustment to different LAA angles and morphologies, as well as a soft distal atraumatic bulb for deep entry into the LAA and very distal deployment. Additionally, the device can be fully retrieved and redeployed multiple times.

Asmarats reported that among 126 consecutive patients treated at 15 centers in Europe and Canada, Ultraseal device success was 97%, major periprocedural adverse events occurred in 2.4%, and the rate of significant pericardial effusion was 0.8%.

The study was simultaneously published online in JACC: Cardiovascular Interventions.

In an accompanying editorial, Kimberly Atianzar, MD, and Sameer Gafoor, MD (both Swedish Heart and Vascular, Seattle, WA), note that in addition to the potential for spurring competition and decreasing cost to payers through the addition of a new LAA closure device, any advanced iteration expands options for operators.

“The use of the articulating hub may be beneficial in sharp takeoffs, which can allow less stress and potentially better approximation of the LAA ostial and landing zone planes for closure,” Atianzar and Gafoor write. “Use of different biomaterials may help us mitigate device-related thrombus.”

Significant Reduction in Stroke, Thromboembolic Event Risk

Three-quarters of patients in the study had a bleeding history and more than 90% were not eligible for oral anticoagulant therapy. While the majority of procedures were executed successful in a mean time of 73 minutes, the device could not be implanted in four patients due to unsuitable anatomy. There was one case of device embolization to the left ventricle within hours of the procedure. According to the authors, this occurred in the period of very early experience and required that the device be retrieved surgically. There were no episodes of in-hospital systemic embolism, major vascular complications, MI, or death.

At a median follow up of 6 months, seven patients had died (5.5%), with none of the deaths attributable to the device. The total rate of ischemic stroke was 2.45% and the rate of thromboembolic events was 3.68%, which translated to approximately a 60% or greater relative risk reduction, according to CHADS2 and CHA2DS2-VASc scores.

Approximately one in five patients had peridevice leak, which was trace or mild in most cases. 

Atianzar and Gafoor note that 5.6% of patients with transesophageal echocardiography follow-up had evidence of device-related thrombus, which is within the range reported in previous studies of patients undergoing LAA closure with either the Watchman or the Amulet. All patients in the study with thrombus were given oral anticoagulation and had complete thrombus resolution and remained asymptomatic with no neurological events during follow-up.

It is possible, the editorialists add, that device-related characteristics can exacerbate or contribute to thrombus, raising questions about whether the articulating joint on Ultraseal may be an issue. Gafoor, who co-moderated the session, told TCTMD in an interview that it is still too early to tell if the Ultraseal configuration may have contribute to the device-related thrombus seen in the study, but said ongoing development of LAA closure devices seems to be going in the direction of avoiding things like connector pins that have been linked to the complication.

“Nevertheless, this is a problem that affects all endocardiac devices and therefore that should be evaluated moving forward,” Gafoor added.

A recent analysis presented at the Heart Rhythm Society 2018 Scientific Sessions suggested that patients who develop thrombus on the Watchman may be at higher risk of stroke or systemic embolism. Whether or not there is a causal relationship has not been definitively established, but the authors of the analysis found that the thrombus and the events occurred within 1 month of each other nearly half of the time.

Another unknown with regard to the Ultraseal relates to the polyvinyl acetate foam component, which is a different material than that used in other commercially available LAA closure devices.

“Whether different materials have different thrombogenic profiles in the left atrium and respond to different anticoagulation and antiplatelet regimens is an area worthy of further investigation,” Atianzar and Gafoor write. “However, in the short term, the decision to move fully away from postprocedural anticoagulation consideration or postprocedural screening is not a justifiable one. The need to monitor patients with single or dual antiplatelet therapy after LAA [occlusion] is higher than ever before, as we have a potential issue (thrombogenicity) and a method to treat it (anticoagulation).”

Ongoing Questions and Metric Mayhem

During his presentation, Asmarats said the Ultraseal is currently being studied in ongoing registries in Canada and Europe and that an investigational device exception (IDE) trial is planned with an expected enrollment of about 1,000 patients.

Ultraseal has nine different bulb sizes, ranging from 16 to 32 mm with the proximal sail being 6 mm larger than the distal bulb diameter, and requires a minimum LAA depth of 16 mm. Asmarats added that the device is particularly well suited to small anatomy.

David R. Holmes Jr, MD (Mayo Clinic, Rochester, MN), the other co-moderator, wondered at the increasing difficulty of developing metrics as newer LAA closure devices emerge. He noted the array of endpoints that could be chosen, including device thrombosis, seal, and whether or not anticoagulation is needed.

“[O]r are we going to have a whole field of these things and you just choose whatever you like? I don’t mean to oversimplify it, but the metrics of evaluating performance is really going to be very hard,” he added.

Furthermore, Holmes said with such low event rates as reported for this initial Ultraseal study, “you’re going to have to study thousands of patients unless you use composite endpoints . . . I think it’s going to be very hard for the field to interpret that.”

As for how the Ultraseal measures up to Watchman and Amulet, Gafoor said with more than 1,000 patients in the Amulet registry and extensive trial and registry data for Watchman, the new device still must prove itself.

“What we do know is the very early data seem promising and also the learning curve from the other two devices seems to be transferable to the Ultraseal,” he observed. “This is in my opinion very promising because new devices can be developed with the same operators being able to easily take them on, and that moves us to what is the efficacy long-term, and that is going to be the discriminating factor by which devices are selected for individual patients.”