1. The index of microvascular resistance measured acutely predicts infarct severity and left ventricular function at 3 months in patients with ST segment elevation myocardial infarction McGeoch RJ 12, Watkins S 1, Berry C 1,2, Davie A 1, Byrne J 1, Hillis WS 1, Lindsay MM 1, Robb SD 1, Dargie HJ 1, Oldroyd KG 1 1Department of Cardiology, Golden Jubilee National Hospital 2BHF Glasgow Cardiovascular Research Centre, Faculty of Medicine, University of Glasgow

2. No conflicts of interest

3. Background Immediate aim of reperfusion therapy in STEMI is to achieve patency of infarct related artery TIMI grade 3 flow achieved 90% of patients 1 Despite this a significant proportion of patients do not achieve complete myocardial perfusion 1. Keeley EC, et al Lancet 2003

4. Microvascular obstruction in STEMI Can effect up to 50 % of patients who undergo successful reperfusion Studies have shown MVO is associated with higher adverse clinical events including heart failure and death. 1,2 No currently agreed gold standard for assessment of MVO in the cath lab 1. Hombach et al Eur Heart J 2005 2. Wu et al Circulation 1998

5. Index of microcirculatory resistance (IMR) using the RADI TM pressure and temperature wire Performed at the time of PCI. Numerical value for myocardial resistance. In vivo and in vitro validation 1,2 Independent of variations in haemodynamic states. 3 IMR = Pd x Tmn 1 1. Aarnoudse W et al Catheter Cardiovasc Interv 2004 2. Fearon W et al Circulation 2004 3. Ng MKC, Yeung AC, Fearon WF Circulation 2006

6. Thermodilution derived mean transit times at rest and hyperaemia

7. Assessment of MVO and LV function by cardiac MRI CMR allows accurate assessment of LV volumes, ejection fraction and visualisation of MVO and infarct size 1 Cannot be performed at the time of emergency PCI when potential interventions would be of maximal benefit 1. Task force of the ESC Eur Heart J. 1998

8. Anterior STEMI

9. Anterior MI – Late gadolinium contrast MVO absent MVO present

10. Hypothesis Microvascular function measured invasively at the time of reperfusion will predict the severity of myocardial injury subsequently revealed by MRI. Specifically, we aimed to determine whether IMR calculated immediately after successful epicardial reperfusion in patients presenting with STEMI could be used as a predictor of MVO and myocardial damage using ceCMR as the gold standard comparison.

11. Flow Diagram of the Study 57 patients with STEMI treated by emergency PCI Initial consent PCI with pressure wire assessment Re-consent ceCMR at 24-48 hours ceCMR at 3 months

12. Methods: physiological assessment PCI performed in line with current international guidelines. Pressure wire (Radi Medical Systems, Uppsala, Sweden) was used as the primary guide-wire. IMR calculated post procedure during maximal hyperaemia (adenosine 140 mcg/kg/min) Mean aortic and distal coronary pressures were recorded during maximal hyperemia.

13. Methods: ceCMR 1.5 T Siemens Avanto ceCMR at 24-48h ceCMR at 3 months Contrast agent: gadolinium-DTPA

15. Demographics Mean age (range) : 58 (32-83)

16. Results: ceCMR Successful physiological measurements where achieved in all patients 53/57 had complete baseline ceCMR 47/57 had complete follow up scans

17. Results: MVO

18. MVO present (n=27) MVO absent (n=26) P value Mean age (SD) 57 (10.1)58 (11.6) Median IMR (IQR) 38.1 (29 – 55) 26.9 (18 – 36) 0.003

19. Predictors of LVEF at baseline Univariate R 2 value P valueMultivariate analysis Smoking5.40.08P = 0.29 Diabetes12.10.008p = 0.03 IMR29.1<0.001p = <0.001

20. Predictors of LVEF at 3 months Univariate R 2 value P value Multivariate analysis Lipidaemia120.01P = 0.017 GP2b3a inhibitor 10.80.02P = 0.014 IMR14.50.007P = 0.004

21. Predictors of Infarct Volumes at Baseline Univariate R 2 value P value Multivariate analysis Lipidaemia3.60.18P = 0.16 GP2b3a inhibitor 5.30.09P = 0.12 IMR18.60.001P = 0.002

22. Predictors of Infarct Volumes at 3 months Univariate R 2 value P valueMultivariate analysis Lipidaemia9.10.04P = 0.07 GP2b3a inhibitor 5.50.11P = 0.09 IMR15.60.006P = 0.008

23. Conclusions IMR is significantly higher in those with MVO as assessed by ceCMR IMR measured acutely at the end of emergency PCI independently predicts infarct size and LV function in the longer term Potentially this relatively simple wire based technique could be used at the time of PCI as a marker of MVO and myocardial damage

24. Acknowledgements Chief Scientist Office Scotland Robertson Centre for Biostatistics, University of Glasgow

25. Correlation between both methods of IMR calculation

26. IMR vs. LVEF at baseline

27. IMR vs. Peak troponin I

28. Results: MVO

29. Predictors of LVEF at baseline Univariate R 2 value P value Multivariate analysis Age 2.60.23 Male 2.60.23 Smoking 5.40.08P = 0.29 Hypercholestorelaemia 0.10.94 Hypertension 0.40.63 Diabetes 12.10.008p = 0.03 GP2b3a inhibitor 3.70.15 Thrombectomy catheter 1.90.31 IMR 29.1<0.001p = <0.001 CFIp 0.70.54 Wedge pressure 0.10.93

30. Predictors of LVEF at 3 months Univariate R 2 value P value Multivariate analysis Age 00.97 Male 2.00.34 Smoking 1.70.37 Hypercholestorelaemia 120.01P = 0.017 Hypertension 0.70.56 Diabetes 2.00.34 GP2b3a inhibitor 10.80.02P = 0.014 Thrombectomy catheter 3.20.22 IMR 14.50.007P = 0.004 CFIp 0.10.81 Wedge pressure 00.95

31. Predictors of Infarct Volumes at Baseline Univariate R 2 value P value Multivariate analysis Age 00.87 Male 0.50.62 Smoking 1.90.33 Hypercholestorelaemia 3.60.18P = 0.16 Hypertension 2.60.25 Diabetes 0.20.77 GP2b3a inhibitor 5.30.09P = 0.12 Thrombectomy catheter 1.20.43 IMR 18.60.001P = 0.002 CFIp 0.80.53 Wedge pressure 0.10.81

32. Predictors of Infarct Volumes at 3 months Univariate R 2 value P value Multivariate analysis Age 0.10.84 Male 1.10.49 Smoking 0.90.52 Hypercholestorelaemia 9.10.04P = 0.07 Hypertension 0.80.55 Diabetes 0.90.52 GP2b3a inhibitor 5.50.11P = 0.09 Thrombectomy catheter 2.80.26 IMR 15.60.006P = 0.008 CFIp 0.40.67 Wedge pressure 0.30.72

33. Inclusion/exclusion criteria Patients aged > 18 ECG and symptomatic evidence of acute STEMI and who undergo emergency PCI. Informed written consent. Standard contraindications to MRI. Contraindications to Gadolinium. Contraindications to adenosine. Cardiogenic shock. Previous myocardial infarction in the same territory as the index event Pregnant