Abstract 19032: Does an Epicardial Coronary Stenosis Affect Microvascular Resistance?
Introduction: Controversy exists regarding the impact of an epicardial coronary stenosis on the minimum achievable microvascular resistance. Some have suggested that minimum achievable microvascular resistance increases in the setting of an epicardial stenosis. The goal of this study is to assess microvascular resistance by measuring the index of microcirculatory resistance (IMR) in patients with high-grade coronary stenosis before and after percutaneous coronary intervention (PCI).
Methods: Patients undergoing elective PCI of the left anterior descending artery (LAD) without prior anterior infarction and without peri-procedural myocardial necrosis were included. A pressure-temperature sensor tipped wire was placed in the distal two-thirds of the LAD and the mean hyperemic transit time (TmnH) of room temperature saline, the hyperemic proximal pressure (Pa), hyperemic distal pressure (Pd) and wedge pressure (Pw) were measured before and after LAD PCI. Hyperemia was induced by adenosine infusion (140μg/kg/min). IMR (Pa x TmnH x [Pd-Pw]/[Pa-Pw]) was derived before and immediately following PCI. A simplified form of IMR (Pd x TmnH), which does not take into account collateral flow, was also calculated before and after PCI.
Results: IMR was measured before and after LAD PCI in 40 patients and did not change significantly (19.5 ±13.0 vs. 19.0 ±11.4 units, p=0.77). When the simplified form of IMR was calculated, it did appear that microvascular resistance was elevated due to the epicardial stenosis and decreased after PCI (28.4 ± 16.9 vs. 20.1 ±11.8 units, p<0.001).
Conclusion: Minimal achievable microvascular resistance is not increased by epicardial stenosis. Prior studies which have suggested otherwise, likely did not account for collateral flow in the determination of microvascular resistance.
- © 2010 by American Heart Association, Inc.