High rates of high on-aspirin platelet reactivity in patients after transcatheter aortic valve implantation
Authors: Hesselbarth D , D'orazio M , Ciccarone G , Gjermeni D , Juelch C , Rilinger J , Breitbart P , Ruile P , Pottgiesser T , Von Zur Muehlen C , Duerschmied D , Westermann D , Olivier C B 
Published: November 2023

Abstract

Background
Guidelines recommend aspirin monotherapy in patients after transcatheter aortic valve replacement (TAVR) without an indication for oral anticoagulation. The prevalence of high on-aspirin platelet reactivity (HAPR) varies from 1% to 34% and may be associated with long-term ischemic risk or subclinical valve thrombosis which occurs in 17-40% of the patients after TAVR.

Purpose
To determine the prevalence of HAPR and its association with subclinical valve thrombosis in patients undergoing TAVR using methods that directly indicate the degree of platelet cyclooxygenase inhibition.

Methods
Data were collected in a prospective, single-center, observational cohort study between October 2020 and June 2022. Patients were enrolled after TAVR, and platelet function was assessed during the hospital stay with light-transmittance platelet aggregation (LTA) and thrombelastography (TEG) platelet mapping. Platelet aggregation was induced with arachidonic acid (AA)-induced LTA (final concentration [fc] 1.64 mM) and TEG (fc 1.0mM). The maximum percent aggregation (%aggr) was recorded. According to the literature, HAPR was defined as &gt;20% aggregation by LTA or &gt;50% aggregation by TEG, respectively. All patients were under maintenance of 100 mg aspirin or received a loading dose of 300-600mg aspirin before measurement. 47 of 75 patients underwent computed tomography (CT) to detect valve thrombosis (VT) 6 months after TAVR.

Results
Data from 75 patients under maintenance of aspirin were analyzed.
The median age was 82 years (interquartile range, IQR 79-85), and 52% were male. 12 patients (16%) had a history of stroke or TIA, and 7 (9%) had suffered a previous myocardial infarction. TEG and LTA were performed during the hospital stay between days 0 and 17 post-TAVR. Median AA-induced maximum aggregation by LTA was 17 % (interquartile range, IQR 13-38) and by TEG was 29 % (IQR 5-64). When determining platelet function using LTA, 33 patients (44%) had residual platelet function (i.e., %aggrLTA &gt;20%) despite aspirin treatment. According to the TEG results, 27 patients (36 %) were identified as HAPR (i.e., %aggrTEG &gt;50%). The agreement (Kappa=0.06) and correlation (r=0.32, Figure 1) between the two tests were low to moderate. 13 patients had HAPR in both methods. 19 of 47 patients (40%) had VT on CT 6 months after TAVI. 12 of these 19 patients (63%) with VT responded well to aspirin in the TEG and LTA, while 7 (37%) had HAPR in both tests. HAPR was not significantly associated with HALT when measured with TEG or LTA (OR 0.90 [95% CI 0.27.2.76], p=0.86 and 0.58 [95% CI 0.17-2.04], p=0.37, respectively; Table 1).

Conclusion
HAPR assessed by LTA and TEG is frequent in patients undergoing TAVR. In this exploratory study, HAPR was not significantly associated with the occurrence of HALT. Further studies are required to evaluate the long-term risk of leaflet thrombosis or thromboembolic events in patients with HAPR.