BOSTON – Device-related thrombus (DRT) does not occur often after left atrial appendage closure with the Watchman device. When it does, however, it is associated with a significantly higher rate of stroke and systemic embolism compared with that of patients with no DRT, according to a recent analysis presented at the annual scientific sessions of the Heart Rhythm Society.

Courtesy Boston Scientific

Given the negative implications of DRT, a judicious surveillance strategy should be considered, especially when DRT risk factors are present, investigators said in a report on the study, which was published simultaneously in Circulation.

“Certainly, DRT is associated with an increased risk of stroke, and therapeutic anticoagulation should be resumed when discovered with rigorous transesophageal echocardiography follow-up to ensure resolution,” noted senior investigator Vivek Y. Reddy, MD.

Despite the higher rates of all strokes, ischemic strokes, and hemorrhagic strokes linked with DRT, the complication did not link with a higher rate of all-cause mortality compared with patients who never had a DRT. The results also suggested a causal link between DRT and subsequent stroke in about half the patients with DRT because their strokes occurred within a month following DRT diagnosis.

Despite these findings, a majority – 74% – of patients with an identified DRT did not have a stroke, and 87% of the strokes that occurred in the patients who received the Watchman device occurred in the absence of a DRT, reported Dr. Reddy, who presented the findings at the meeting.

The most immediate implication of the findings is the strong case they make for rethinking the timing of planned follow-up transesophageal echocardiography (TEE) examinations of patients after they receive a Watchman device. The current, standard protocol schedules a TEE at 45 days after Watchman placement, when routine anticoagulation usually stops, and then a second TEE 12 months after placement. A better schedule might be to perform the first TEE 3-4 months after Watchman placement to give a potential DRT time to form once oral anticoagulant therapy stops, suggested Dr. Reddy, professor and director of the cardiac arrhythmia service at Mount Sinai Hospital and Health System in New York.

“Surveillance is very important. I don’t think DRT usually occurs unless anticoagulation is suboptimal or stops.” Dr. Reddy noted that he and his associates are analyzing the best time for TEE surveillance in other large databases of patients treated with left atrial appendage (LAA) closure. Newer models of LAA closure devices structurally modified to reduce thrombus formation are nearing clinical use, he added.

The analysis, believed to be the largest to date of DRT following left atrial appendage closure, was based on prospective data from four clinical trials. That included two randomized controlled trials, PROTECT AF and PREVAIL, as well as the CAP and CAP2 prospective registries.

Among 1,739 patients in those studies receiving an implant, 65 (3.74%) had DRT, the investigators found.

Over 1 year of follow-up, 25% of patients with DRT had an ischemic stroke or systemic embolism, versus 6.8% of patients without DRTs (P less than .001), they reported. That worked out to an event rate of 6.28 and 1.65 events per 100 patient years, respectively.

The strongest predictors of DRT in multivariable analysis included vascular disease, history of stroke or transient ischemic attack, permanent atrial fibrillation, and left atrial appendage diameter, according to the report. Conversely, increasing left ventricular ejection fraction was protective against DRT.

Taken together, these data support reevaluating the transesophageal echocardiography strategy, according to Dr. Reddy and his coauthors. Those approaches might include targeting patients with DRT risk factors, routine additional surveillance at 6 months, or delaying the first transesophageal echocardiography to 4 months.

“Importantly, none of these strategies have been rigorously compared, so these suggestions are subject to future studies,” the researchers wrote.

“DRT remains a problem despite increased operator experience with LAA occlusion and improved occluding devices,” commented David B. De Lurgio, MD, a cardiac electrophysiologist at Emory Healthcare in Atlanta. “What is a little alarming is that the risk for DRT extends beyond the period of prescribed anticoagulation. Although the risk from DRT mitigates the benefit of LAA closure compared with warfarin, it does not mitigate the benefit from occlusion compared with no treatment,” said Dr. De Lurgio, designated discussant for the report. “Prevention and management of DRT may require that each patient receive a tailored regimen of anticoagulation and surveillance.”

The Watchman studies were funded by Boston Scientific, the company that markets the device. Dr. Reddy has been a consultant to and has received research funding from Boston Scientific and from Abbott and Biosense-Webster, and he reported having an equity interest in Javelin and Surecor. Coauthors reported disclosures related to Boston Scientific, Johnson & Johnson, Abbott, and other medical device companies. Dr. De Lurgio has been a consultant to Boston Scientific.

Updated, 5/17/18: This article has been updated with reporting from Mitchel L. Zoler at the meeting, and has been revised for clarity and to reflect that the results were presented by Dr. Reddy.

SOURCE: Dukkipati SR et al. Circulation. 2018 May 11. doi: 10.1161/CIRCULATIONAHA.118.035090.

Device-related thrombus associated with ischemic events