Persistent high on-treatment platelet reactivity in acute coronary syndrome

Platelet Inhibition, Endothelial Function, and Clinical Outcome in Patients Presenting With ST-Segment-Elevation Myocardial Infarction Randomized to Ticagrelor Versus Prasugrel Maintenance Therapy: Long-Term Follow-Up of the REDUCE-MVI Trial

Background

Off‐target properties of ticagrelor might reduce microvascular injury and improve clinical outcome in patients with ST‐segment–elevation myocardial infarction. The REDUCE‐MVI (Evaluation of Microvascular Injury in Revascularized Patients with ST‐Segment–Elevation Myocardial Infarction Treated With Ticagrelor Versus Prasugrel) trial reported no benefit of ticagrelor regarding microvascular function at 1 month. We now present the follow‐up data up to 1.5 years.

Methods and Results

We randomized 110 patients with ST‐segment–elevation myocardial infarction to either ticagrelor 90 mg twice daily or prasugrel 10 mg once a day. Platelet inhibition and peripheral endothelial function measurements including calculation of the reactive hyperemia index and clinical follow‐up were obtained up to 1.5 years. Major adverse clinical events and bleedings were scored. An intention to treat and a per‐protocol analysis were performed. There were no between‐group differences in platelet inhibition and endothelial function. At 1 year the reactive hyperemia index in the ticagrelor group was 0.66±0.26 versus 0.61±0.28 in the prasugrel group (P=0.31). Platelet inhibition was lower at 1 month versus 1 year in the total study population (61% [42%–81%] versus 83% [61%–95%]; P<0.001), and per‐protocol platelet inhibition was higher in patients randomized to ticagrelor versus prasugrel at 1 year (91% [83%–97%] versus 82% [65%–92%]; P=0.002). There was an improvement in intention to treat endothelial function in patients randomized to ticagrelor (P=0.03) but not in patients randomized to prasugrel (P=0.88). Major adverse clinical events (10% versus 14%; P=0.54) and bleedings (47% versus 63%; P=0.10) were similar in the intention‐to‐treat analysis in both groups.

Conclusions

Platelet inhibition at 1 year was higher in the ticagrelor group, without an accompanying increase in bleedings. Endothelial function improved over time in ticagrelor patients, while it did not change in the prasugrel group.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique Identifier: NCT02422888.

The pharmacodynamics of low and standard doses of ticagrelor in patients with end stage renal disease on hemodialysis

BACKGROUND

Patients with end-stage renal disease (ESRD) on maintenance hemodialysis (HD) respond poorly to clopidogrel. We assessed the utility of low-dose ticagrelor in ESRD patients on maintenance HD.

METHODS

In this single-center, prospective, randomized pharmacodynamic study, 52 ESRD patients on HD were prescribed clopidogrel (300mg loading dose [LD], then 75mg daily), standard-dose ticagrelor (180mg LD, then 90mg twice daily), or low-dose ticagrelor (90mg LD, then 90mg daily) for 14days. Platelet function was evaluated before and after therapy via light transmittance aggregometry and the VerifyNow™ P2Y₁₂ assay.

RESULTS

The adenosine diphosphate (ADP)-induced maximal extent of platelet aggregation differed significantly between the low-dose ticagrelor and clopidogrel groups (ANCOVA, p=0.04 after stimulation with 5μmol/L ADP; p<0.01 after stimulation with 20μmol/L ADP). Inhibition of platelet aggregation increased significantly in the order of clopidogrel, low-dose ticagrelor, and standard-dose ticagrelor, as revealed by adjusted intergroup comparison analysis (ANCOVA, p=0.04 after stimulation with 5μmol/L ADP; p=0.005 after stimulation with 20μmol/L ADP). The rates of onset of the antiplatelet effect curves from 0 to 5h after administration of the LDs were greater in the standard- and low-dose ticagrelor groups than in the clopidogrel group. Significant sequential reductions in P2Y₁₂ reaction units were noted, in the following order: clopidogrel, low-dose ticagrelor, and standard-dose ticagrelor (ANCOVA, p<0.001). No bleeding occurred in the low-dose ticagrelor group.

CONCLUSIONS

Low-dose ticagrelor afforded greater platelet inhibition than did clopidogrel in ESRD patients on HD.