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Angiographic Coronary Slow Flow Is Not a Valid Surrogate for Invasively Diagnosed Coronary Microvascular Dysfunction
Michael Mayer1, Tess Allan1, Kenneth L Harkin2
1Department of Cardiology, University of Chicago, Chicago, Illinois, USA.
Insights
Coronary slow flow on angiography is weakly linked to invasive measures of coronary microvascular dysfunction (CMD). Angiographic slow flow should not replace invasive testing for diagnosing CMD.
Area of Science:
- Cardiology
- Vascular Biology
- Diagnostic Imaging
Background:
- Coronary microvascular dysfunction (CMD) is a common cause of ischemia with no obstructive coronary arteries.
- Current diagnostic criteria for CMD include assessing slow coronary flow using corrected TIMI frame count (cTFC).
- The relationship between angiographic slow flow (cTFC) and invasive coronary function testing (CFT) for CMD diagnosis remains unclear.
Purpose of the Study:
- To evaluate the correlation between cTFC and invasive CFT parameters in diagnosing CMD.
- To determine if angiographic slow flow is a reliable indicator of microvascular dysfunction.
Main Methods:
- Adult patients with ischemia and no obstructive coronary arteries underwent invasive CFT.
- Measurements included baseline coronary blood flow, coronary flow reserve (CFR), and index of microcirculatory resistance (IMR).
- Coronary slow flow was defined as cTFC >25 and CMD was defined by abnormal CFR and/or IMR.
Main Results:
- Of 508 adults, 49% had coronary slow flow.
- Slow flow was associated with higher odds of abnormal IMR but lower odds of abnormal CFR.
- cTFC showed weak correlations with baseline coronary blood flow, CFR, and IMR.
Conclusions:
- Coronary slow flow demonstrates a weak association with invasive CFT results.
- Angiographic slow flow should not be utilized as a substitute for invasive diagnostic methods for CMD.
Background:
Ischemia with no obstructive coronary arteries is frequently caused by coronary microvascular dysfunction (CMD). Consensus diagnostic criteria for CMD include baseline angiographic slow flow by corrected TIMI (Thrombolysis In Myocardial Infarction) frame count (cTFC), but correlations between slow flow and CMD measured by invasive coronary function testing (CFT) are uncertain.
Objectives:
The aim of this study was to investigate relationships between cTFC and invasive CFT for CMD.
Methods:
Adults with ischemia with no obstructive coronary arteries underwent invasive CFT with thermodilution-derived baseline coronary blood flow, coronary flow reserve (CFR), and index of microcirculatory resistance (IMR). CMD was defined as abnormal CFR (<2.5) and/or abnormal IMR (≥25). cTFC was measured from baseline angiography; slow flow was defined as cTFC >25. Correlations between cTFC and baseline coronary flow and between CFR and IMR and associations between slow flow and invasive measures of CMD were evaluated, adjusted for covariates. All patients provided consent.
Results:
Among 508 adults, 49% had coronary slow flow. Patients with slow flow were more likely to have abnormal IMR (36% vs 26%; P = 0.019) but less likely to have abnormal CFR (28% vs 42%; P = 0.001), with no difference in CMD (46% vs 51%). cTFC was weakly correlated with baseline coronary blood flow (r = -0.35; 95% CI: -0.42 to -0.27), CFR (r = 0.20; 95% CI: 0.12 to 0.28), and IMR (r = 0.16; 95% CI: 0.07-0.24). In multivariable models, slow flow was associated with lower odds of abnormal CFR (adjusted OR: 0.53; 95% CI: 0.35 to 0.80).
Conclusions:
Coronary slow flow was weakly associated with results of invasive CFT and should not be used as a surrogate for the invasive diagnosis of CMD.
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