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IMPORTANCE Percutaneous coronary intervention (PCI) of nonculprit vessels among patients with ST-segment elevation myocardial infarction (STEMI) is associated with improved clinical outcome compared with culprit vessel-only PCI. Fractional flow reserve (FFR) and coronary flow reserve are hyperemic indices used to guide revascularization. Recently, instantaneous wave-free ratio was introduced as a nonhyperemic alternative to FFR. Whether these indices can be used in the acute setting of STEMI continues to be investigated. OBJECTIVE To assess the value of hemodynamic indices in nonculprit vessels of patients with STEMI from the index event to 1-month follow-up. DESIGN, SETTING, AND PARTICIPANTS This substudy of the Reducing Micro Vascular Dysfunction in Revascularized STEMI Patients by Off-target Properties of Ticagrelor (REDUCE-MVI) randomized clinical trial enrolled 98 patients with STEMI who had an angiographic intermediate stenosis in at least 1 nonculprit vessel. Patient enrollment was between May 1, 2015, and September 19, 2017.After successful primary PCI, nonculprit intracoronary hemodynamic measurements were performed and repeated at 1-month follow-up. Cardiac magnetic resonance imaging was performed from 2 to 7 days and 1 month after primary PCI. MAIN OUTCOMES AND MEASURESThe value of nonculprit instantaneous wave-free ratio, FFR, coronary flow reserve, hyperemic index of microcirculatory resistance, and resting microcirculatory resistance from the index event to 1-month follow-up. RESULTSOf 73 patients with STEMI included in the final analysis, 59 (80.8%) were male, with a mean (SD) age of 60.8 (9.9) years. Instantaneous wave-free ratio (SD) did not change significantly (0.93 [0.07] vs 0.94 [0.06]; P = .12) and there was no change in resting distal pressure/aortic pressure (mean [SD], 0.94 [0.06] vs 0.95 [0.06]; P = .25) from the acute moment to 1-month follow-up. The FFR decreased (mean [SD], 0.88 [0.07] vs 0.86 [0.09]; P = .001) whereas coronary flow reserve increased (mean [SD], 2.9 [1.4] vs 4.1 [2.2]; P < .001). Hyperemic index of microcirculatory resistance decreased and resting microcirculatory resistance increased from the acute moment to follow-up. The decrease in distal pressure from rest to hyperemia was smaller at the acute moment vs follow-up (mean [SD], 10.6 [11.2] mm Hg vs 14.1 [14.2] mm Hg; P = .05). This blunted acute hyperemic response correlated with final infarct size (ρ, -0.29; P = .02). The resistive reserve ratio was lower at the acute moment vs follow-up (mean [SD], 3.4 [1.7] vs 5.0 [2.7]; P < .001). CONCLUSIONS AND RELEVANCEIn the acute setting of STEMI, nonculprit coronary flow reserve was reduced and FFR was augmented, whereas instantaneous wave-free ratio was not altered. These results may be explained by an increased hyperemic microvascular resistance and a blunted adenosine responsiveness at the acute moment that was associated with infarct size.

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Background: Despite successful restoration of epicardial vessel patency with primary percutaneous coronary intervention (pPCI), coronary microvascular injury (MVI) occurs in a large proportion of STEMI patients, adversely affecting clinical and functional outcome. Ticagrelor has been reported to increase plasma adenosine levels, which might have a protective effect on the microcirculation. We investigated if ticagrelor maintenance therapy after revascularized STEMI is associated with less MVI compared to prasugrel maintenance therapy. Methods: A total of 110 STEMI patients received a loading dose of ticagrelor and were randomized to maintenance therapy of ticagrelor (n=56) or prasugrel (n=54) after pPCI. The primary outcome was MVI at 1 month, as determined with the index of microcirculatory resistance (IMR) in the infarct-related artery. Cardiovascular magnetic resonance imaging was performed during the acute phase and at one month. Results: The primary outcome of IMR was not superior in ticagrelor or prasugrel treated patients (ticagrelor 21 [15-39] U, prasugrel 18 [11-29] U, p=0.08). Recovery of microcirculatory resistance over time was not better in patients with ticagrelor versus prasugrel (ticagrelor-13.9 U vs. prasugrel-13.5 U, p=0.54). Intramyocardial hemorrhage was observed less frequently in patients with ticagrelor (23% vs. 43%, p=0.04). At one month no difference in infarct size was observed (ticagrelor 7.6 [IQR 3.7-14.4] g, prasugrel 9.9 [IQR 5.7-16.6] g, p=0.17). The occurrence of microvascular obstruction was not different in patients on ticagrelor (28%) or prasugrel (41%, p=0.35). Plasma adenosine concentrations were not different during the index procedure and during maintenance therapy with ticagrelor or prasugrel. Conclusions: In patients with STEMI, ticagrelor maintenance therapy was not superior to prasugrel in preventing MVI in the infarct-related territory as assessed by IMR and this resulted in a comparable infarct size at one month.

Upper limb function was not affected when coronary catheterizations and interventions were performed through the radial artery.

In Response:In response to the comments of Chugh et al on our study, 1 we would like to point out that the rate of radial artery occlusion (RAO) ranged from <1% to 30% in recent studies (mean 7.89%), whereas in the Rotterdam Radial Access Research study, this was <4% at all time points. 1 The incidence of RAO varies and seems multifactorial, including anatomic substrate (ie, vessel size), access technique, and access management before, during, and after the procedure. Our study underscores the clinical importance of number of radial punctures to obtain arterial access and its association with RAO, radial pulse loss, and pain and discomfort. In contrast, radial artery size at baseline, which was handled as a continuous variable in our model, had no impact on RAO. We agree with Chugh et al that smaller radial artery size may result in serial puncture attempts. In fact, the median radial inner lumen at baseline in our study was 2.25 mm in patients receiving 1 puncture and 2.01 mm in those receiving >1 puncture. However, a lumen of <2.00 mm did not predict RAO at any time point in our study, confirming our hypothesis that the number of punctures could independently predict RAO.The use of low-dose heparin for short-lasting transradial diagnostic studies resembles standard practice in many institutions throughout the world. Systematic use of a higher heparin dose in a diagnostic setting may result in less RAO, especially when patent hemostasis could not be achieved.2 Still, full anticoagulation is associated with a significant increase in access site bleeding with no further benefit on RAO in a recent, large, double-blind randomized trial.3 Similarly, Pancholy et al 4 demonstrated that shorter compression times (2 versus 6 hours) also reduced RAO. Shorter compression time (15 minutes) with newer compression devices was associated with a higher bleeding rate. Noteworthy, kaolin-filled pads allow for short compression, but evidence on their efficacy is still limited, and these pads were not available in our institution at the time of the trial. 5The Rotterdam Radial Access Research (R-RADAR) study introduced novel noninvasive ultrasound imaging technology in the space of transradial access. Its relatively small sample size precludes any firm conclusions, yet we believe the findings in terms of arterial injury and healing after transradial access are original, refine current understanding and should spur further research to optimize planning, execution, and postprocedural management of transradial procedures. DisclosuresNone. Francesco