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Differential Interaction of High Microvascular Resistance With Coronary Flow Reserve Across Coronary Microvascular
Ahmet Tas1, Yaren Alan2, Peter Damman3
1Department of Cardiology, Amsterdam UMC, Heart Centre, Amsterdam Cardiovascular Sciences, the Netherlands; Emergency Department, Gomec State Hospital, Balikesir, Turkey.
Insights
Patients with high hyperemic microvascular resistance (hMR) but normal coronary flow reserve (CFR) show favorable coronary and aortic hemodynamics. This suggests that high hMR alone may not indicate poor prognosis in stable coronary syndromes.
Area of Science:
- Cardiovascular Physiology
- Coronary Artery Disease
- Microvascular Function
Background:
- Increased minimal hyperemic microvascular resistance (hMR) lacks prognostic relevance in stable chronic coronary syndromes, unlike reduced coronary flow reserve (CFR).
- Understanding the hemodynamic implications of different coronary microvascular dysfunction (CMD) endotypes is crucial for accurate prognostication.
Purpose of the Study:
- To investigate local and systemic hemodynamics in relation to CMD and hMR.
- To analyze diastolic rate constant and arterial reservoir function (Pr-Pxs) in different CMD endotypes.
Main Methods:
- Comparison of four endotypes: functional CMD (CFR <2.5; hMR <2.5), structural CMD (CFR <2.5; hMR ≥2.5), no CMD-low hMR (CFR ≥2.5; hMR <2.5), and no CMD-high hMR (CFR ≥2.5; hMR ≥2.5).
- Utilized generalized linear mixed models, adjusting for multiple coronary arteries per patient.
- Assessed diastolic rate constant (s⁻¹) and reservoir-excess pressure (Pr-Pxs) parameters.
Main Results:
- CMD endotypes exhibited higher diastolic rate constants and lower Pr/Pxs, indicating systemic relative hyperemia and altered arterial compliance.
- The no CMD-high hMR group showed the lowest Pxs, distinct from structural CMD.
- Higher hMR was associated with lower CFR in CMD cases but not in the no CMD group.
Conclusions:
- Patients with high hMR and normal CFR demonstrate favorable coronary and aortic hemodynamic profiles.
- This suggests that high hMR in the absence of reduced CFR may be associated with beneficial hemodynamic characteristics.
Background:
In contrast to reduced coronary flow reserve (CFR), increased minimal hyperemic microvascular resistance (hMR) lacks prognostic relevance in stable chronic coronary syndromes.
Objectives:
The aim of the study is to investigate the local and systemic hemodynamics, including diastolic rate constant (s-1) and arterial reservoir function (reservoir-excess pressure [Pr-Pxs] parameters), as they relate to coronary microvascular dysfunction (CMD; CFR <2.5) and hMR.
Methods:
Functional CMD (CFR <2.5; hMR <2.5, nvessel = 82, npatient = 77), structural CMD (CFR <2.5; hMR ≥2.5, nvessel = 160, npatient = 149), no CMD-low hMR (CFR ≥2.5; hMR <2.5, nvessel = 44, npatient = 42), and no CMD-high hMR(CFR ≥2.5; hMR ≥2.5, nvessel = 26, npatient = 26) endotypes were compared using generalized linear mixed models adjusting for the multiple coronary arteries within same patients.
Results:
CMD endotypes were associated with a higher diastolic rate constant (s-1; functional-CMD: 2.0 [1.7-2.2], structural-CMD: 1.9 [1.7-2.1], no CMD-low hMR: 1.5 [1.3-1.7]; no CMD-high hMR 1.5 [1.4-1.6]; P = 0.006) and lower Pr/Pxs (functional CMD: 18.8 [17.6-20.1]; structural CMD: 19.6 [18.5-20.8]; no CMD-low hMR: 21.9 [20.1-23.8]; no CMD-high hMR: 23.8 [22.4-25.2], P < 0.001), suggesting a systemic relative hyperemic state, with lower vasotonus and arterial compliance irrespective of high hMR. Despite similar hMR, No CMD-high hMR endotype distinctively had the lowest Pxs (mm Hg) (4.0 [3.4-4.6]), whereas structural CMD (5.1 [4.8-5.4]) had the highest Pxs (P < 0.001). In no CMD, a milder increase in hMR accompanied higher basal microvascular resistance than CMD (β = 0.128 [0.106-0.149], P < 0.001; β = 0.167 [0.155-0.180], P < 0.001; P = 0.002). Higher hMR was associated with lower CFR in the CMD cases (β = -0.057 [-0.082 to -0.033], P < 0.001), but not in the no CMD group (β = 0.066 [0.013-0.118] P = 0.014).
Conclusions:
In this hypothesis-generating study, patients with high hMR-normal CFR exhibit favorable characteristics of coronary and aortic hemodynamics and reservoir function.
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