Abstract 11365: The Index of Microcirculatory Resistance Does Not Change Following Emergency Percutaneous Intervention in St-elevation Myocardial Infarction
Background: The status of the coronary microvasculature is increasingly recognised as an important determinant of myocardial reperfusion in the setting of ST elevation myocardial infarction (STEMI). We investigated whether stent implantation at the time of emergency percutaneous coronary intervention (PCI) for STEMI altered the index of microcirculatory resistance (IMR) and whether any changes in IMR post stenting correlated with the extent of myocardial damage assessed using biomarkers and cardiac MRI.
Methods: Comprehensive physiological assessment using a coronary pressure/temperature tipped guide-wire pre and post stenting was performed in 65 patients undergoing emergency intervention for STEMI. Hyperaemia was induced using intravenous adenosine infusion in a dose of 140 μ g/kg/min. True IMR [IMR (true)] was calculated using Pa x Tmn ([pd-wd]/[pa-wd]) accounting for collateral flow and apparent IMR [IMR (app)] calculated using IMR = Pd x Tmn. Patients underwent cardiac MRI imaging at 2 days and 2 months post PCI.
Results: Successful coronary physiological measurements were made in all patients before and after stenting. There was no difference in IMR (true) 35.5 [23-58] pre stenting and IMR (app) 30.6 [20.1-52.6] after stenting; p = 0.12. There was no significant change in IMR in those given glycoprotein 2b3a inhibitors and those whom underwent aspiration thrombectomy. In those in whom IMR increased post stenting there was a significant decrease in ejection fraction at 2 days but this did not extend out to 2 months.
Conclusions: Microvascular resistance does not change significantly following emergency percutaneous intervention in patients with ST elevation myocardial infarction when collateral flow is accounted for. This suggests that stent deployment itself is not detrimental to the status of the coronary microvasculature, and furthermore, that mechanical reperfusion of the infarct related epicardial artery does not achieve optimal treatment of the coronary microcirculation.
- © 2012 by American Heart Association, Inc.