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. 2024 Apr 8;17(7):920-929.
doi: 10.1016/j.jcin.2024.02.025.

Angiographic Coronary Slow Flow Is Not a Valid Surrogate for Invasively Diagnosed Coronary Microvascular Dysfunction

Michael Mayer  1 , Tess Allan  1 , Kenneth L Harkin  2 , Ethan Loftspring  2 , Seyed E Saffari  1 , Harmony R Reynolds  2 , Jonathan Paul  1 , Rohan Kalathiya  1 , Atman P Shah  1 , Sandeep Nathan  1 , Mary C McCarthy  3 , Nathaniel R Smilowitz  4 , Steven E S Miner  5 , John Blair  6
Affiliations

Angiographic Coronary Slow Flow Is Not a Valid Surrogate for Invasively Diagnosed Coronary Microvascular Dysfunction

Michael Mayer et al. JACC Cardiovasc Interv. .

Abstract

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.

Keywords: angina; coronary angiography; coronary artery disease; microvascular angina.

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Conflict of interest statement

Funding Support and Author Disclosures Dr Reynolds is supported by in-kind donations for research from Abbott Vascular, Philips, SHL Telemedicine, and Siemens. Dr McCarthy has received speaking honoraria and payments as a content expert for educational materials from Abbott Vascular. Dr Smilowitz is supported in part by the National Heart, Lung, and Blood Institute of the National Institutes of Health (award K23HL150315); and has served on an advisory board and as a consultant for Abbott Vascular. Dr Miner has received unrestricted research grants and speaking honoraria from Abbott Vascular. Dr Blair has served on an advisory board, as a consultant, and on the Speakers Bureau for Abbott Vascular. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Figures

Figure 1:
Figure 1:. Correlation between the corrected TIMI frame count (cTFC) with baseline coronary blood flow, coronary flow reserve, and index of microcirculatory resistance.
A. A modest correlation between cTFC and baseline coronary blood flow (r=−0.35 [95% CI −0.42 - −0.27], p<0.001) was observed. B. A weak correlation between cTFC and coronary flow reserve (r=0.20 [95% CI 0.12 – 0.28], p<0.001) was observed. C. A weak correlation between cTFC and the index of microcirculatory resistance (0.16 [95% CI 0.07 – 0.24], p=0.002) was observed.
Figure 2.
Figure 2.. Central Illustration. Angiographic coronary slow flow and results of invasive coronary function testing
508 patients with ischemia and no obstructive coronary arteries underwent coronary angiography and invasive coronary function testing with thermodilution-derived coronary flow reserve (CFR) and index of microcirculatory resistance (IMR). CMD was defined as abnormal CFR<2.5 and/or abnormal IMR≥25. Coronary slow flow was defined as cTFC > 25. Angiographic slow flow was moderately associated with baseline coronary blood flow, was not associated with CMD (abnormal CFR and/or IMR) and was associated with lower odds of abnormal CFR.
See this image and copyright information in PMC

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