Coronary Microvascular Dysfunction in Ischemia With Nonobstructive Coronary Arteries and Associations With Sublingual Microvascular Abnormalities.

BACKGROUND

Coronary microvascular dysfunction (CMD) is a mechanism of ischemia with nonobstructive coronary arteries (INOCA) diagnosed by invasive coronary function testing (CFT). It is unknown whether CMD reflects a systemic microcirculatory disorder. Sidestream darkfield (SDF) microscopy permits noninvasive imaging of red blood cells (RBCs) in the sublingual microcirculation.

OBJECTIVES

We sought to evaluate whether SDF microscopy identifies sublingual microvascular abnormalities in patients with INOCA due to CMD.

METHODS

Adults with INOCA underwent CFT for CMD, defined by abnormal coronary flow reserve <2.5 or index of microcirculatory resistance ≥25. Sublingual SDF microscopy was performed to determine the endothelial glycocalyx perfused boundary region (PBR), RBC filling percentage (%RBC), and perfused microvascular density (PMVD).

RESULTS

A total of 135 participants with INOCA (mean age 59.3 ± 12.1 years, 80% female) underwent CFT and sublingual SDF microscopy. CMD was present in 63 participants (46.7%). The median PBR was 1.96 (IQR: 0.4), median %RBC was 72.6 (IQR: 8.0), and median PMVD was 406 (IQR: 141). No differences in sublingual PBR, %RBC, and PMVD were observed by CMD status. No correlations between sublingual parameters and continuous measures of coronary flow reserve or index of microcirculatory resistance were observed.

CONCLUSIONS

Noninvasive SDF microscopy did not identify sublingual microvascular abnormalities in INOCA patients with CMD.