Coronary microvascular dysfunction (CMD) is a paramount factor involved in the development of anginal syndromes. Among patients with angina and nonobstructive coronary artery disease with CMD, two patterns have been identified using minimal microvascular resistance: structural CMD, and functional CMD.

Structural CMD is characterized by decreased coronary flow reserve (CFR) in the presence of increased microvascular resistance. This subtype represents changes in the microvasculature such as arteriolar obliteration, which improves under conditions of maximal vasodilatation.

However, functional CMD is characterized by decreased CFR with normal or decreased microvascular resistance. This is related to increased myocardial oxygen demand or impaired coronary autoregulation. However, the prognostic relevance of these two CMD subtypes has not been evaluated.

The aim of this (multicenter, retrospective) ILIAS Registry was to evaluate the prognostic impact of structural vs. functional CMD in patients with nonobstructive coronary artery disease.

This study analyzed 1102 patients. Mean patient age was 63 years old, and 69% of subjects were male. The most analyzed artery was the anterior descending artery, followed by the circumflex artery. Patients were classified into four groups based on CFR (cutoff value <2.5), and two groups based on microvascular resistance: low and high (in terms of the microvascular resistance index [MRI] and the hyperemic microvascular resistance [HMR]).

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Regarding the results, abnormal CFR values were associated with increased risk of MACE and treated vessel failure (TVF) at 5 years regardless of the values of microvascular resistance obtained. However, abnormal microvascular resistance values were not associated with increased MACE and TVF. Lastly, there were no differences between normal or abnormal microvascular resistance values in patients with normal CFR.

Conclusion

CMD, represented as a decrease in CFR, was associated with an increase in MACE and FVL at a 5-year follow-up. In contrast, microvascular resistance was not associated with adverse clinical events. In patients with CMD, there were no significant differences in MACE and TVF between structural CMD and functional CMD.

Original Title: Prognostic value of structural and functional coronary microvascular dysfunction in patients with non-obstructive coronary artery disease; from the multicentre international ILIAS registry.

Reference: Coen K.M. Boerhout et al EuroIntervention 2022;18.

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