The risk for a composite of death, ischemic stroke, and systemic embolization was twofold higher in the DRT cohort than in the control cohort (29.5% vs. 14.4%; hazard ratio, 2.37; 95% CI, 1.58-3.56) and driven by a higher rate of ischemic stroke (16.9% vs. 3.6%; HR, 3.49; 95% CI, 1.35-9.00).
The incidence of bleeding and intracerebral hemorrhage, however, was similar in the DRT and control cohorts.
One of the surprises of the study was that medications prescribed in the short term after LAA closure were not associated with DRT, Dr. Alkhouli said. A previous meta-analysis of 66 studies by the investigators also found that antithrombotic regimen did not explain the heterogeneity of DRT formation.
“I think we’ll have to take that with a grain of salt, because there’s so many variations in the practice, and this is observational data. But that, in my mind, brings up a mechanistic issue,” he said.
It’s often recommended “that we should put patients on blood thinners for 3 months or 6 weeks, or whatever it is, to decrease the chance of thrombus, assuming the patients will have a normal endothelialization of the device,” Dr. Alkhouli said.
“Well, we know that’s not the reality,” he continued. “We know many patients don’t endothelialize, and, even if some patients do, there may be some endothelial damage. So I think the whole mechanism of prescribing a little bit of a blood thinner to avoid that risk may be missing the point. It’s a bit more complex than that, evidenced also by the fact that three-fourths of all the DRTs happened after 45 days, when patients are typically not taking a blood thinner.”
Based on the five independent risk factors, the investigators created a clinical DRT risk score that assigned 1 point for renal insufficiency, implantation depth greater than 10 mm from the pulmonary ridge, and nonparoxysmal AFib; and 4 points for iatrogenic pericardial effusion and for hypercoagulability disorder. Low risk was categorized as 1 point and high risk as 2 or more points.
The presence of one major risk factor or two minor risk factors, for example, led to a 2.1-fold increased risk for DRT, compared with those with no DRT risk factors.
The risk score will require validation in a prospective cohort but is “a step forward in addressing DRT” and triaging patients, Dr. Alkhouli said. The findings highlight the need to avoid deep device implantation and the importance of shared decision-making with patients, especially with those at high risk.
“And third, which is most important, I think, in my mind, is that it tells us not to put a blind eye to this topic and just say with improved devices it will go away,” he said. “That’s a bit unrealistic.”
In an accompanying editorial, Oussama Wazni, MD, Walid Saliba, MD, and Ayman A. Hussein, MD, all from the Cleveland Clinic, write that “the study sheds light on this yet unresolved issue, and the observations may help with risk stratification and optimization of procedural techniques.”
Whereas many of the nonmodifiable risk factors are helpful in shared decision-making decisions, they continue, “knowledge of these risk factors may not preclude implantation in patients who are otherwise at risk of both stroke off anticoagulation and bleeding on anticoagulation.”
Dr. Wazni and colleagues acknowledge that the small number of events in the study limits statistical power for definitive conclusions and say that further studies are needed to clarify the natural history of DRTs and their management, resolution, and impact on cardiovascular events.
Practitioners should also continue to cautiously assess for LAAO clinical indications for implant, according to the editorialists, who point out that the regulatory approval language in the United States was “flexible and nonspecific.”
“As the field grows wider, enhancing LAAO safety with optimal design, implantation, and periprocedural management is critically important, yet the main focus should remain on optimal patient selection for the purpose of achieving safe and successful outcomes,” the editorialists conclude.
Dr. Alkhouli has served as a consultant for Boston Scientific. Coauthor disclosures are listed in the paper. Dr. Wazni and Dr. Hussein have received research grant support from Boston Scientific. Dr. Wazni and Dr. Saliba have been consultants for Boston Scientific.
A version of this article first appeared on Medscape.com.