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Comparative Visual Analysis of Coronary Slow Flow and Myocardial Blush Grade in Relation to Invasive Testing for
Andrew P Hill1, Ryan L Wallace1, Abhishek Chaturvedi1
1Section of Interventional Cardiology, MedStar Washington Hospital Center, Washington, District of Columbia, USA.
Insights
Angiographic coronary slow flow and myocardial blush grade do not reliably detect coronary microvascular dysfunction (CMD) in patients with angina and non-obstructive coronary arteries. Invasive coronary functional testing is recommended for suspected CMD.
Area of Science:
- Cardiology
- Vascular Biology
- Diagnostic Imaging
Background:
- Coronary slow flow (CSF) and abnormal myocardial blush grade (MBG) are linked to coronary microvascular dysfunction (CMD) and adverse outcomes.
- The diagnostic accuracy of these angiographic markers compared to invasive methods for CMD is not well-established.
Purpose of the Study:
- To evaluate the correlation between angiographic assessments of CSF and MBG and gold-standard invasive coronary functional testing (CFT) for CMD diagnosis.
Main Methods:
- The Coronary Microvascular Disease Registry identified patients with angina and non-obstructive coronary arteries (ANOCA) undergoing invasive CFT.
- CMD was defined by invasive bolus thermodilution (coronary flow reserve < 2.5 and index of microcirculatory resistance > 25).
- CSF and MBG were assessed angiographically and compared between CMD-positive and negative groups.
Main Results:
- Of 304 patients, 26.6% had CMD. No significant differences were observed in the rates of abnormal CSF (8.6% vs. 4.9%) or slow Thrombolysis in Myocardial Infarction frame count (14.8% vs. 15.7%) between CMD-positive and negative groups.
- Similarly, the rates of abnormal MBG were comparable (1.3% vs. 3.1%) across groups.
- Patient demographics showed CMD-positive individuals were slightly older and had lower BMIs.
Conclusions:
- Angiographic CSF and MBG are not reliable indicators of CMD in ANOCA patients.
- Invasive CFT should be considered for definitive CMD diagnosis when clinically suspected.
Background:
Angiographic coronary slow flow (CSF) has been correlated with coronary microvascular dysfunction (CMD) and abnormal myocardial blush grade (MBG) has been associated with worse outcomes in acute myocardial infarction. Their validity has not been compared with newer invasive forms of coronary functional CMD testing. Therefore, we aimed to investigate whether angiographic assessment of CSF and MBG correlate with gold-standard invasive assessments of CMD.
Methods:
Using the Coronary Microvascular Disease Registry (NCT05960474), we identified patients with angina and non-obstructive coronary arteries (ANOCA) who underwent invasive coronary functional testing (CFT) between August 2021 and August 2024. CMD was defined as coronary flow reserve (CFR) < 2.5 with an index of microcirculatory resistance (IMR) > 25 using invasive bolus thermodilution technique. CSF was defined as > 3 cardiac cycles for distal opacification of vessels with contrast. Slow Thrombolysis in Myocardial Infarction frame count (TFC) was defined as a corrected frame count of > 25. MBG was categorized as abnormal (Grade 0 or 1). Rates of abnormal CSF and MBG were compared between the CMD-positive and negative groups.
Results:
A total of 304 patients were included, of whom 81 (26.6%) were CMD positive. Patients were predominantly female (67.9 vs. 63.7%, p = 0.50) and slightly older (64.0 ± 11.3 vs. 60.6 ± 10.8 years, p = 0.02) with a lower BMI (28.5 ± 5.7 vs. 31.6 ± 6.9; p < 0.001) in the CMD positive group. Common comorbidities included hypertension, hyperlipidemia, and diabetes with a similar prevalence in both groups. There was no difference between CMD-positive and negative groups for CSF, (8.6% vs. 4.9%, p = 0.23) or slow cTFC (14.8% vs. 15.7%, p = 0.85). Additionally, the rate of abnormal MBG was similar in both groups (1.3% vs. 3.1%; p = 0.37).
Conclusion:
Our findings suggest that, while readily available and previously used for diagnosis, the angiographic findings of CSF and MBG do not reliably indicate the presence of CMD in ANOCA patients. Therefore, dedicated CFT should be pursued if there is clinical suspicion of CMD.
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