In the present study, we aimed to clarify whether VASP-guided clopidogrel MD could decrease adverse clinical events in AF patients requiring anticoagulation and scheduled for PCI.

This was a prospective cohort study that included consecutive patients with stable coronary artery disease who had AF requiring anticoagulation and were scheduled for PCI. Patients were included if they 1) were older than 18 years and no more than 80 years, 2) had a preexisting diagnosis of paroxysmal, persistent, or permanent AF with anticoagulation therapy warfarin, 3) had effort angina pectoris despite optimal medical therapy, and 4) had silent ischaemia on radionuclide imaging. Exclusion criteria included cardiac arrest, New York Heart Association III/IV function, platelet count < 100 × 10⁹/L, creatinine clearance rate < 25 mL/min.

We included patients from Shanghai East Hospital, a teaching hospital of Tongji University serving a population of approximately 5,500,000, with 12 intervention specialists and 2000 PCI procedures each year. Five hundred patients were randomly allocated to the VASP-guided and control groups. A statistician performed the allocation. Blinding was used for the participants and/or researchers. We collected data on demographic and clinical characteristics, prothrombotic risk factors, and antithrombotic therapy strategies before and after PCI. Patients’ thromboembolism risk was evaluated by the CHA₂DS₂-VASc (Congestive heart failure, 1 point; Hypertension, 1 point; Age ≥ 75 years, 2; Diabetes mellitus, 1 point; Stroke/transient ischaemic attack, 2; Vascular disease, 1 point; Age 65–74 years, 1 point; Sex category for 1) score. Bleeding risk was assessed by the HAS-BLED (Hypertension, 1; Abnormal renal and liver function, 1 point each; Stroke/thromboembolism, 1 point; Bleeding history, 1 point; Labile INR [international normalised ratio], 1 point; Elderly [age > 65 years], 1 point; Drug consumption and alcohol abuse, 1 point each) score. All procedures were performed according to the rules of the Ethical Committee on human clinical trials and according to the Helsinki Declaration revised in 2008. Informed written consent was obtained from all participants. The name of the registry was “Prospective randomized controlled study of anti-platelet therapy in atrial fibrillation patients undergoing percutaneous coronary intervention”.

AF was defined as paroxysmal, persistent, permanent, or unknown according to guidelines [4]. Stroke was defined as the sudden loss of neurologic function, which was classified into ischaemic or haemorrhagic and verified by brain computed tomography or magnetic resonance imaging [5]. Systemic embolism was diagnosed as acute vascular obstruction of the limbs or any organ and was verified by angiography. Acute myocardial infarction (AMI) was defined according to the universal definition of the ESC/ACCF/AHA/WHF [6]. Stent thrombosis (ST) was defined according to the Academic Research Consortium standard [7]. Thrombolysis in myocardial infarction (TIMI) major bleeding included intracranial or clinically significant haemorrhage with a haemoglobin decrease > 50 g/L according to the TIMI criteria [8]. Minor bleeding was also defined according to the TIMI criteria [8].

PCI was performed in accordance with international guidelines, using a standard technique, through the radial or femoral route [9]. A drug-eluting stent (DES) was used based on the angiography outcome. An intravenous bolus of unfractionated heparin (100 IU/kg) was administered immediately before the procedure. The administration of glycoprotein IIb/IIIa inhibitors was decided on by the attending cardiologists.

Warfarin was stopped 3 days before PCI and patients were treated with low-molecular-weight heparin until 12 h before PCI. A combined loading dose of 300 mg aspirin and 600 mg clopidogrel was used before PCI. After PCI, a combined administration of 100 mg aspirin, 75 mg clopidogrel, and INR-monitored warfarin was continued for 3 months according to guidelines [9]. The clopidogrel MD (Plevix, 75 mg per tablet, SANOFI, France, and clopidogrel bisulfate tablets, 25 mg per tablet, SALUBRIS, China) fluctuated between 75 and 225 mg for at least 1 year. All patients were treated with TT for 3 months, followed by clopidogrel plus warfarin for 9 months. VASP-adjusted clopidogrel MD commenced at the beginning of 3 months and was modified according to the VASP index in order to keep the platelet reaction index (PRI) below 50%. VASP was monitored at 3, 6, 9, and 12 months after PCI. The stepwise increase of clopidogrel dosage was adopted. After the first PRI monitoring, 100 mg clopidogrel was administered if PRI > 50%. The second PRI monitoring was undertaken 6 months after PCI, and 125 mg clopidogrel was administered if PRI was still > 50%. Subsequent additional doses were similar to the previous doses. Another 25 mg clopidogrel was given if PRI > 50% after every 3 months. The maximum clopidogrel MD at the end of 1 year was 175 mg. If PRI < 25%, clopidogrel MD was decreased to 75 mg. If PRI > 25% and was < 50%, the dose was not changed and the determined dose was maintained.

Three months after PCI, blood samples were drawn from the antecubital vein once every 3 months. The initial blood was removed to avoid platelet activation induced by the puncture action. Blood was transferred into a tube with 3.8% trisodium citrate. The tube was gently inverted up and down 3 to 5 times and was immediately sent to the monitoring laboratory.

The VASP phosphorylation test was performed more than 1 h after blood collection by an experienced technician using Platelet VASP kits (Becton Dickinson, USA) according to the instruction manual [10]. Briefly, blood samples were mixed in vitro with adenosine diphosphate (ADP) and/or prostaglandin E1 (PGE1). Each blood sample was incubated with a 16C2FITC antibody, followed by a goat anti-mouse fluorescence staining in isothiocyanate polyclonal reagent. Flow cytometric monitoring was conducted with a Coulter EPICS XL cytometer (CA, U.S.A). The platelet group was identified on its side scatter and forward distributions. Every 3000 platelet events were gated and analysed for mean fluorescence intensity (MFI) using flow cytometry. The MFI corresponding to each experimental situation (ADP and ADP + PGE1) was determined to calculate a ratio directly related to the VASP phosphorylation value. The ratio, [(MFI_PGE1-MFI_{ADP + PGE1})/MFI_PGE1] × 100%, which indicates a percentage of platelet reactivity, is expressed as a PRI corresponding to a ratio of activated platelets versus resting platelets.

For all patients who received warfarin, the predicted INR was set between 2.0 and 2.5 according to guidelines [2]. INR was regularly monitored after discharge. In the beginning, INR evaluations were performed every week after discharge. If the INR achieved the target range after monitoring three consecutive times, the measurement was then taken monthly.

For the clinical follow-up, the primary endpoint was designated as the occurrence of MACCE, involving cardiovascular death, myocardial infarction (MI), target vessel revascularisation (TVR), ST, systemic embolism, and stroke. Secondary endpoints were defined as TIMI major and minor bleeding.

The clinical follow-up involved a clinic visit or telephone interview at 3, 6, 9, and 12 months after PCI. If a dose adjustment was made at 9 months, the patients were followed up for another 1 year from then on. The MD modification was as before. All patients with symptoms during the visit and interview were evaluated by at least two cardiologists. Death or MI events were recorded by hospital admission staff or community service.

For patients prescribed antithrombotic therapy after discharge, there was high compliance in both groups. The median duration of TT and clopidogrel plus warfarin was 3.2 and 9.5 months, respectively. There was no difference in duration between CHA₂DS₂-VASc 1 or ≥ 2 and HASBLED ≤2 or ≥ 3 (Table 2).

We analysed PRI at a mean time of 3, 6, 9, and 12 months after the PCI procedure. The baseline PRI showed no significant difference between both groups (73.5 ± 12.7% [VASP] vs 68.4 ± 17.2% [control], P = 0.4). PRI in the VASP-guided group decreased significantly (73.5 ± 12.7%, 32.3 ± 4.9%, 35.5 ± 6.7%, and 29.8 ± 7.3% at 3, 6, 9, and 12 months after randomisation, respectively; P = 0.001); PRI in the control group also decreased, but not significantly (68.4 ± 17.2%, 48.5 ± 13.2%, 51.6 ± 19.8%, and 65.3 ± 17.2%, respectively; P > 0.5). Compared to the control group, PRI in the VASP-guided group was significantly lower (P = 0.04, 0.03, and < 0.001 at 6, 9, and 12 months after randomisation, respectively) (Table 3).

Clopidogrel MD in the VASP-guided group was modified according to PRI. The number of patients that required clopidogrel MD individualisation was 162 (67.3%), 181 (75.4%), 197 (81.9%), and 208 (86.3%) at 3, 6, 9, and 12 months, respectively (Fig. 2). Regarding MD according to PRI at 3, 6, 9, and 12 months, 132 (81.5%), 100 (55.2%), 70 (35.5%), and 40 (19.4%) patients, respectively, had increased MD, 22 (13.6%), 41 (22.6%), 93 (47.2%), and 130 (63.1%) patients, respectively, had unchanged MD, while 8 (4.9%), 40 (22.1%), 34 (17.3%), and 36 (17.5%) patients, respectively had decreased MD (Fig. 3). At the study’s completion, 33 of 241 (13.7%) patients in the VASP-guided group still had HTPR> 50% (data not shown).

During the 1-year follow-up, INR was measured at least every month. The representative value at 1, 3, 6, 9 and 12 months are listed in Table 4. INR increased at 12 months compared to baseline only in patients with CHA₂DS₂-VASc score ≥ 2 (from 1.9 ± 0.3 to 2.5 ± 0.8, P < 0.05).

Complete follow-up (median 365 days; range 300 to 395 days) was recorded in 95.6% of the whole cohort. The clinical events recorded in the two groups are shown in Table 5. The incidences of TVR and all MACCE were higher in the control group than in the VASP-guided group, whereas the occurrence of cardiovascular death, MI, ST, systemic embolism, and stroke was not significantly different between both groups. Regarding the secondary endpoints, major bleeding incidence was comparable between both groups, whereas the rate of minor bleeding was significantly higher in the VASP-guided group (15.3% vs 9.7%, P = 0.032). Kaplan-Meier survival analysis demonstrated that there was no statistical difference between the VASP-guided and control groups during the 1-year follow-up (log-rank test P = 0.68) (Fig. 4).

There are some limitations to the present study. First, the study was conducted in the Chinese population, which demonstrates more “clopidogrel resistance” than the European and North American populations, so the conclusion should be cautiously extended to others. Second, the sample of patients recruited in the present study was relatively small. Third, the present study did not evaluate the effects of the new antiplatelet ticagrelor or new anticoagulants such as dabigatran or rivaroxaban. In the future, we will focus on the antithrombotic effect of these antagonists.