Preconditioning, collateral recruitment and adenosine

Ticagrelor and preconditioning in patients with stable coronary artery disease (TAPER-S): a randomized pilot clinical trial

Background

Ticagrelor is a reversibly binding, direct-acting, oral, P₂Y₁₂ antagonist used for the prevention of atherothrombotic events in patients with coronary artery disease (CAD). Ticagrelor blocks adenosine reuptake through the inhibition of equilibrative nucleoside transporter 1 (ENT-1) on erythrocytes and platelets, thereby facilitating adenosine-induced physiological responses such as an increase in coronary blood flow velocity. Meanwhile, adenosine plays an important role in triggering ischemic preconditioning through the activation of the A1 receptor. Therefore, an increase in ticagrelor-enhanced adenosine bioavailability may confer beneficial effects through mechanisms related to preconditioning activation and improvement of coronary microvascular dysfunction.

Methods

To determine whether ticagrelor can trigger ischemic preconditioning and influence microvascular function, we designed this prospective, open-label, pilot study that enrolled patients with stable multivessel CAD requiring staged, fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI). Participants will be randomized in 1:1 ratios either to ticagrelor (loading dose (LD) 180 mg, maintenance dose (MD) 90 mg bid) or to clopidogrel (LD 600 mg, MD 75 mg) from 3 to 1 days before the scheduled PCI. The PCI operators will be blinded to the randomization arm. The primary endpoint is the delta (difference) between ST segment elevations (in millimeters, mm) as assessed by intracoronary electrocardiogram (ECG) during the two-step sequential coronary balloon inflation in the culprit vessel. Secondary endpoints are 1) changes in coronary flow reserve (CFR), index of microvascular resistance (IMR), and FFR measured in the culprit vessel and reference vessel at the end of PCI, and 2) angina score during inflations. This study started in 2018 with the aim of enrolling 100 patients. Based on the rate of negative FFR up to 30% and a drop-out rate up to 10%, we expect to detect an absolute difference of 4 mm among the study arms in the mean change of ST elevation following repeated balloon inflations. All study procedures were reviewed and approved by the Ethical Committee of the Catholic University of Sacred Heart.

Discussion

Ticagrelor might improve ischemia tolerance and microvascular function compared to clopidogrel, and these effects might translate to better long-term clinical outcomes.

Trial registration

EudraCT No. 2016–004746-28. No. NCT02701140. 

Trial status

Information provided in this manuscript refers to the definitive version (n. 3.0) of the study protocol, dated 31 October 2017, and includes all protocol amendments. Recruitment started on 18 September 2018 and is currently ongoing. The enrollment is expected to be completed by the end of 2019.

Trial sponsor

Fondazione Policlinico Universitario A. Gemelli – Roma, Polo di Scienze Cardiovascolari e Toraciche, Largo Agostino Gemelli 8, 00168 Rome, Italy.

Protective effect of pre-infarction angina on microvascular obstruction after primary percutaneous coronary intervention is blunted in humans by cardiovascular risk factors

BACKGROUND

Pre-infarction angina (PIA) has been shown to reduce the microvascular obstruction (MVO) rate in patients with ST-segment elevation myocardial infarction (STEMI). We sought to evaluate the potential modulator role of cardiovascular risk factors (CRFs) on this protective effect.

METHODS AND RESULTS

Two hundred patients with STEMI were enrolled. PIA was defined as typical chest pain within the 48 h preceding STEMI onset. Angiographic MVO was defined as TIMI flow grade <2 or TIMI flow 3 with myocardial blush grade <2; electrocardiographic (ECG) MVO was defined as ST-segment elevation resolution <70%. Common CRFs were collected. In the absence of hypertension, both angiographic and ECG MVO rates were lower in patients with PIA as compared with those without, whereas, in the presence of hypertension, they were similar in both study groups (P for interaction=0.01 and P=0.014, respectively). Among nonsmokers, angiographic and ECG MVO rates were lower in patients with PIA as compared with those without, whereas within smokers, they were similar in both study groups (P for interaction=0.037 and P=0.037, respectively). In the absence of dyslipidemia, the angiographic and ECG MVO rates were lower in patients with PIA as compared with those without, whereas within dyslipidemic patients, they were similar in both study groups (P for interaction=0.012 and P=0.04, respectively).

CONCLUSIONS

The protective effect of PIA on MVO is blunted by CRFs.