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Reference values for intracoronary Doppler flow velocity-derived hyperaemic microvascular resistance index
Rutger G T Feenstra1, Andreas Seitz2, Coen K M Boerhout1
1Amsterdam UMC, Heart Center, Department of Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands.
Insights
This study establishes a reference range for the hyperemic microvascular resistance index (HMR) in patients with angina and no obstructive coronary artery disease. An HMR threshold greater than 2.5 mmHg/cm/s can identify abnormal microvascular resistance in clinical practice.
Area of Science:
- Cardiology
- Vascular Physiology
- Diagnostic Medicine
Background:
- Invasive assessment of microvascular function is crucial for diagnosing chronic coronary syndromes.
- Angina with no significant epicardial coronary obstruction (ANOCA) requires accurate microvascular assessment.
Purpose of the Study:
- Establish a reference range for the Doppler flow velocity-derived hyperemic microvascular resistance index (HMR).
- Define HMR norms in ANOCA patients without structural coronary alterations.
Main Methods:
- Utilized a cohort of ANOCA patients with coronary flow reserve (CFR) >2.5.
- Established HMR reference range using non-parametric methods.
- Correlated HMR with clinical characteristics via Spearman rank analysis.
Main Results:
- Median HMR was 1.6 mmHg/cm/s in 41 patients.
- The 95% population reference range for HMR was 0.8 to 2.7 mmHg/cm/s.
- No significant correlations found between HMR and clinical characteristics.
Conclusions:
- The upper limit of normal for HMR in the reference population is 2.6-2.7 mmHg/cm/s.
- An HMR threshold >2.5 mmHg/cm/s can identify abnormal microvascular resistance.
- This provides a valuable tool for clinical practice in ANOCA patients.
Background:
Invasive assessments of microvascular function are rapidly becoming an integral part of physiological assessment in chronic coronary syndromes.
Objective:
We aimed to establish a reference range for Doppler flow velocity-derived hyperaemic microvascular resistance index (HMR) in a cohort of angina with no significant epicardial coronary obstruction (ANOCA) patients with no structural pathophysiological alterations in the coronary circulation.
Methods:
The reference population consisted of ANOCA patients undergoing invasive coronary vasomotor function assessment who had a coronary flow reserve (CFR) >2.5, and had either (1) tested negatively for spasm provocation (n = 12) or (2) tested positively with only angina at rest (n = 29). A reference range for HMR was established using a non-parametric method and correlations with clinical characteristics were determined using a spearman rank correlation analysis.
Results:
In 41 patients median HMR amounted to 1.6 mmHg/cm/s [Q1, Q3: 1.3, 2.2 mmHg/cm/s]. The reference range for HMR that is applicable to 95% of the population was 0.8 mmHg/cm/s (90% CI: 0.8-1.0 mmHg/cm/s) to 2.7 mmHg/cm/s (90% CI: 2.6-2.7 mmHg/cm/s). No significant correlations were found between HMR and clinical characteristics.
Conclusion:
In this reference population undergoing invasive coronary vasomotor function testing, the 90% confidence interval of the HMR upper limit of normal ranges from 2.6 to 2.7 mmHg/cm/s. A > 2.5 mmHg/cm/s HMR threshold can be used to identify abnormal microvascular resistance in daily clinical practice.
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