Abstract 16346: Assessment of the Index of Microcirculatory Resistance After Percutaneous Coronary Intervention in Patients with Non-ST-Segment Elevation Myocardial Infarction
Background: The state of the coronary microcirculation is an important determinant of patient prognosis. The index of microcirculatory resistance (IMR) is a recently developed measure of microvascular function, and its capability to predict microvascular function and myocardial viability in patients with ST-segment elevation myocardial infarction has been reported. However, little is known regarding microvascular resistance after PCI in patients with non-ST-segment elevation myocardial infarction (NSTEMI). The aim of this study is to evaluate the IMR values in NSTEMI patients.
Methods: In 28 NSTEMI patients, IMR was measured after successful PCI (less than 20% residual stenosis with TIMI3 flow grade) and the patients were divided into two groups by the median IMR value. The clinical and demographic data were evaluated between these two groups. IMR measurement was performed with a pressure-temperature sensor-tipped coronary wire during maximal hyperemia induced by intravenous adenosine triphosphate administration. The association of IMR values with TIMI risk score and Grace risk score were also assessed. Further, the IMR values of NSTEMI were compared with those of age- and gender-matched 30 patients with stable angina pectoris after PCI.
Results: In NSTEMI, the median IMR value was 26.5 U (IQR17.8-39.8). When increased IMR threshold was defined as 32 U, 9 (32%) patients showed increased microvascular resistance. There was no significant difference in peak cTnI (3.25 [0.90-10.8] vs 2.72 [1.17-15.2], p=0.83), peak CK (226.0 [138.0-630.0] vs 237.5 [121.0-481.0], p=0.82), peak CK-MB (23.5 [14.0-54.0] vs 25.5 [18.0-79.0], p=0.52), ejection fraction (58.1±8.5 vs 62.4±7.3, p=0.16), TIMI risk score (3.6±1.5 vs 3.0±1.3, p=0.24), Grace risk score (141 [125-158] vs 130 [112-143], p=0.33), fractional flow reserve after PCI, and other examined patient and lesion characteristics between the two groups. In SAP, the median IMR value was 14.9 (IQR12.1-32.9), and significantly smaller than that of NSTEMI.
Conclusion:Microvascular dysfunction of the territory at risk is present in nearly 30% of NSTEMI patients following successful PCI, despite achievement of TIMI3 flow. Increased IMR was not predicted by known clinical and demographic variables.
- © 2012 by American Heart Association, Inc.