Abstract 14679: Microcirculatory Flow and Resistance at Rest and Hyperemia in Relation to Major Adverse Cardiovascular Events in Chronic Coronary Syndrome

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Background: The prognostic implications of coronary microvascular dysfunction in an all-comer cohort with chronic coronary syndrome (CCS) are not known. Aim: To investigate the association of baseline resistance index (BRI), index of microcirculatory resistance (IMR), and thermodilution-derived resting- and hyperemic flow velocities (RFV and HFV) with the primary composite endpoint consisting of all-cause mortality, incident myocardial infarction (MI) or hospitalization due to congestive heart failure (CHF) in CCS. Methods: CCS patients undergoing elective coronary angiography (CA) were included. Measurements of corrected IMR, BRI and mean transit time at baseline (Tmn base ) and during hyperemia (Tmn hyp ) were obtained in the LAD. RFV and HFV were calculated as 1/Tmn base and 1/Tmn hyp , respectively. Cox-regression was performed and Kaplan-Meier plots were constructed. Results: We included 503 patients before the coronary anatomy was known and thermodilution measurements in the LAD were obtained in 413 patients. Median age was 68 (IQR 61-74), 127 (25%) were women and 151 (37%) had a flow-limiting epicardial lesion in the LAD. Median follow-up was 5.3 years (IQR 3.0-6.6) and there were 57 events. Log 10 BRI was inversely associated with the primary endpoint before and after fractional flow reserve (FFR) adjustments (HR 0.64 [95% CI 0.42 - 0.97]; Figure 1A). Log 10 IMR was not associated with the primary endpoint (HR 0.94 [95% CI 0.61 - 1.5]; Figure 1B). Log 10 RFV was associated with the primary endpoint before and after FFR- adjustment (HR 1.8 [95% CI 1.2 - 2.7]) whereas log 10 HFV was not (HR 1.2 [95% CI 0.75-1.8]). Conclusion: Low microcirculatory resting resistance and high coronary resting flow velocity in the LAD, indicating impaired autoregulation, were associated with all-cause death, MI and/or CHF in CCS whereas hyperemic microcirculatory resistance and flow were not. Resting flow indices can be used for risk evaluation in patients with CCS undergoing CA. .