Abstract 18705: Regional Variability of Microcirculatory Resistance After Successful Percutaneous Coronary Intervention

Abstract

Background: The main drawback of Fractional Flow Reserve (FFR) measurements occurs in the presence of microvascular disease, as FFR does not take into consideration the contribution of abnormal microvascular resistance. Normal FFR with concomitant microcirculatory disease may be a cause of angina symptoms or myocardial ischemia. Recently, the blood flow in the myocardium has been reported to show significant spatial heterogeneity. We assessed the hypothesis that heterogeneity of regional microvascular resistance exists in patients after successful percutaneous coronary intervention (PCI). Methods and Results: FFR and the index of microcirculatory resistance (IMR) were measured after successful PCI in 20 patients with native de novo discrete coronary lesions both in the territory of the culprit vessel and in the reference territory of non-culprit vessel. Hyperemic mean transmit time (Tmn) was used for the assessment of coronary flow. FFR value after PCI was 0.89 (IQR 0.82-0.96). IMR value in the culprit vessel was 18.8 (IQR 12.1-25.7), and 19.05 (IQR 14.3-26.7) in the non-culprit vessel, respectively. There was no significant relationship between these two regional measurements (r 2 =0.0128, p=ns). Mean difference between these two measures was 17.4 ± 15.9. The coefficients of variation of IMR were 75.7% in the culprit vessel, and 59.5% in the non-culprit vessel. There was a significant relationship between IMR and Tmn both in the culprit vessels (r=0.968, p<0.0001) and non-culprit vessels (r=0.913, p<0.0001). Conclusion: A considerable regional heterogeneity of coronary perfusion and microvascular resistance were observed in the present study. There is a high inter-subject, intra-subject, and interregional variability of coronary flow and microvascular resistance in patients after successful PCI. These results highlight the difficulty in establishing the limits of normal microvascular resistance or vasodilating response in patients with ischemic heart disease.