Key result
High hyperemic microvascular resistance in vessels with preserved coronary flow reserve was associated with robust autoregulatory capacity and increased accelerating wave energy proportion (P=0.042).
Why the study?
The pathophysiological relevance of high hyperemic microvascular resistance in stable coronary artery disease with unobstructed arteries is controversial, particularly regarding its impact on coronary wave energetics and microvascular dysfunction.
Does high hyperemic microvascular resistance without coronary microvascular dysfunction affect coronary wave energetics in patients with unobstructed coronary arteries?
Observational (n=258)
Does high hyperemic microvascular resistance without coronary microvascular dysfunction affect coronary wave energetics in patients with unobstructed coronary arteries?
p-value: p=0.042
High hyperemic microvascular resistance alone is not a definitive marker of coronary microvascular dysfunction and may represent an adaptive state with preserved autoregulatory capacity.
High hMR without CMD may reflect preserved autoregulation rather than dysfunction; leaves open whether wave energetics distinguish microvascular endotypes.
Aims The pathophysiological relevance of high hyperemic microvascular resistance (hMR) in stable coronary artery disease is controversial. Using wave intensity analysis (WIA, defined as the product of the time derivatives of the coronary pressure and velocity), we aim to compare the impact of high hMR on coronary wave energetics with respect to coronary microvascular dysfunction (CMD), defined as reduced coronary flow reserve (CFR < 2.5), in unobstructed arteries. Methods and results The study population (n = 258, mean age = 68 ± 10 years, 73% male) had a high cardiovascular risk profile including dyslipidemia (88%), hypertension (70%), smoking (55%) and diabetes (28%). The mean fractional flow reserve was 0.89 ± 0.05. Vessels (n = 312) were divided into four endotypes: no CMD-low hMR (CFR ≥ 2.5, hMR < 2.5 mmHg.s.cm−1), Functional CMD (CFR < 2.5, hMR < 2.5 mmHg.s.cm−1), Structural CMD (CFR < 2.5, hMR ≥ 2.5 mmHg.s.cm−1), and no CMD-high hMR (CFR ≥ 2.5, hMR ≥ 2.5 mmHg.s.cm−1). The no CMD-high hMR endotype had the lowest mean resting velocity (bAPV = 10 ± 3 cm.s−1 P < 0.001), highest mean basal microvascular resistance (bMR = 9 ± 2 mmHg/cm.s−1 P < 0.001) amongst all endotypes, yet, it had reference-level CFR, microvascular resistance reserve and resistive reserve ratio (P > 0.05 for all compared to no CMD-low hMR), unlike CMD endotypes (P < 0.05 compared to CMD endotypes). The no CMD–high hMR endotype exhibited the highest hyperemic increase in the accelerating wave energy proportion (AEP) (13% ± 13%, P = 0.042), indicating an intact autoregulatory response. Only in the CMD endotypes, high hMR was associated with reduced AEP (r = −0.229, P < 0.001), unlike no CMD endotypes (P = 0.383). Conclusion High hMR alone is not a definitive CMD marker. In line with the adaptive high hMR hypothesis, increased hMR does not necessarily limit augmentation of AEP, and is associated with robust autoregulatory capacity in vessels with preserved CFR. Cardiologists should be alert to a potential adaptive no CMD–high hMR endotype to avoid misdiagnosis. Registration NCT02328820.
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Taş et al. (2025) conducted an observational in Stable coronary artery disease (n=258). High hyperemic microvascular resistance (hMR) vs. Low hMR was evaluated on Accelerating wave energy proportion (AEP) (p=0.042). High hyperemic microvascular resistance in vessels with preserved coronary flow reserve was associated with robust autoregulatory capacity and increased accelerating wave energy proportion (P=0.042).
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