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			<p>How does coronary stent implantation impact on the status of the microcirculation during primary percutaneous coronary intervention in patients with ST-elevation myocardial infarction?</p>

			<p>Giovanni Luigi De Maria1, Florim Cuculi1,2, Niket Patel1, Sam Dawkins1, Gregor Fahrni1, George Kassimis1, Robin P. Choudhury3,4, John C. Forfar1, Bernard D. Prendergast1, Keith M. Channon1, Rajesh K. Kharbanda1&dagger;,<br />
			and Adrian P. Banning1*&dagger;</p>

			<p>1Oxford Heart Centre, NIHR Biomedical Research Centre, Oxford University Hospitals, Headley Way, Oxford OX39DU, UK; 2Department of Cardiology, LuzernerKantonsspital, Luzern, Switzerland; 3Acute Vascular Imaging Centre, Radcliffe Department of Medicine, University of Oxford, Oxford, UK; and 4Division of Cardiovascular Medicine, BHF Centre of Research Excellence, University of Oxford, Oxford, UK</p>

			<p>Received 13 February 2015; revised 27 May 2015; accepted 6 July 2015; online publish-ahead-of-print 7 August 2015</p>

			<p>See page 3178 for the editorial comment on this article (doi:10.1093/eurheartj/ehv495)</p>
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			<td style="background-color:rgb(95.000000%, 97.000000%, 90.000000%)"><img alt="page1image9896" src="file:///page1image9896" style="height:6.009400; width:504.000000" />
			<p>Aims Primary percutaneous coronary intervention (PPCI) is the optimal treatment for patients presenting with ST-elevation myocardial infarction (STEMI). An elevated index of microcirculatory resistance (IMR) reflects microvascular function and when measured after PPCI, it can predict an adverse clinical outcome. We measured coronary microvascular func-</p>

			<p>tion in STEMI patients and compared sequential changes before and after stent implantation.</p>

			<p>.....................................................................................................................................................................................</p>

			<p>Methods and results</p>

			<p>In 85 STEMI patients, fractional flow reserve, coronary flow reserve, and IMR were measured using a pressure wire</p>

			<p>(Certus, St Jude Medical, St Paul, MN, USA) immediately before and after stent implantation. Stenting significantly im-</p>

			<p>proved all of the measured parameters of coronary physiology including IMR from 67.7 [interquartile range (IQR):</p>

			<p>56.2&ndash;95.8] to 36.7 (IQR: 22.7&ndash;59.5), P , 0.001. However, after stenting, IMR remained elevated (.40) in 28</p>

			<p>(32.9%) patients. In 15 of these patients (17.6% of the cohort), only a partial reduction in IMR occurred and these pa-</p>

			<p>tients were more likely to be late presenters (pain to wire time .6 h). The extent of jeopardized myocardium [stan-</p>

			<p>dardized beta: 20.26 (IMR unit/Bypass Angioplasty Revascularization Investigation score unit), P: 0.009] and</p>

			<p>pre-stenting IMR [standardized beta: 20.34 (IMR unit), P: 0.001] predicted a reduction in IMR after stenting (DIMR 1&frasl;4</p>

			<p>post-stenting IMR 2 pre-stenting IMR), whereas thrombotic burden [standardized beta: 0.24 (IMR unit/thrombus score</p>

			<p>unit), P: 0.01] and deployed stent volume [standardized beta: 0.26 (IMR unit/mm3 of stent), P: 0.01] were associated with</p>

			<p>a potentially deleterious increase in IMR.</p>

			<p>.....................................................................................................................................................................................</p>

			<p>Conclusion Improved perfusion of the myocardium by stent deployment during PPCI is not universal. The causes of impaired micro- vascular function at the completion of PPCI treatment are heterogeneous, but can reflect a later clinical presentation and/or the location and extent of the thrombotic burden.</p>

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			<p>Keywords ST-elevation myocardial infarction &dagger; Stent &dagger; Index of microcirculatory resistance &dagger; Distal embolization</p>
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