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In the Platelet Inhibition and Patient Outcomes (PLATO) study, compared with clopidogrel, ticagrelor has shown impressive cardiovascular benefits for patients with acute coronary syndrome (ACS). There are no available data related to coronary circulation after chronic treatment of ticagrelor in patients with ACS who have altered resting coronary blood flow dynamics due to advanced coronary artery disease.
This study was a non-blinded, open label, parallel-group, prospective, randomized controlled clinical trial performed in a single center. To assess myocardial blood flow (MBF), we used N-13 ammonia positron emission tomography (PET) imaging. Participants were randomized to receive ticagrelor 90 mg twice daily or clopidogrel 75 mg once daily after at least 6 months. Rest and stress MBF were measured using N-13 ammonia PET among PLEIO patients at 6-month follow-up visit. Myocardial flow reserve was calculated as stress MBF divided by rest MBF. Data were analyzed on a per-patient and per-vessel basis.
N-13 ammonia PET imaging was performed in 94 patients. Of the 94 patients, 46 were in the ticagrelor group, and 48 in the clopidogrel group. There was no discontinuation of antiplatelet therapy among the patients for 6 months. Compliance was more than 95% for both groups, and concurrent medications were similar. The 2 groups were well-balanced with respect to baseline characteristics. Resting MBF was similar (0.69±0.20 vs. 0.70±0.21, P=0.89) between the two groups. However, hyperemic MBF and myocardial flow reserve of ticagrelor group were significantly higher compared with clopidogrel (1.75±0.46 vs. 1.52±0.59, P=0.03 and 2.71±0.89 vs. 2.20±0.81, P=0.02, respectively). We analyzed 223 non-culprit vessels of registered patients using the results of physiological measures performed during the 6-month follow-up. Rest MBF (0.77±0.25 vs. 0.78±0.18, P=0.87), hyperemic MBF (1.95±0.55 vs. 1.74±0.66, P=0.80), and myocardial flow reserve (2.60±0.75 vs. 2.32±0.79, P=0.56) were not different between the ticagrelor and the clopidogrel group.
We compared the effects of ticagrelor and clopidogrel on MBF over a 6-month follow-up period among patients with ACS treated with percutaneous coronary intervention. Maintenance treatment of ticagrelor increased hyperemic MBF and increased myocardial flow reserve compared with clopidogrel. These differences were not observed in non-culprit vessels.