Abstract
Objective To evaluate the correlation between the TIMI frame count, IMR, and CFR in coronary microvascular disease (slow flow phenomenon). Methods TFC and IMR were recorded in the nitroglycerin and ATP administration states, and the relationship between TFC, IMR, and CFR in specific states was analyzed. Results A total of 41 patients with baseline TFC >25 frames on coronary angiography were enrolled, and nitroglycerin reduced TFC by 50% from baseline in 24 (58.54%) patients; 16 of the remaining 17 patients were able to achieve a 50% reduction in TFC by further intracoronary ATP injection. 10 patients were further tested for IMR, and the results showed significant correlations between baseline TFC and IMR (r = 0.775, P=0.008), TFC and IMR after nitroglycerin (r = 0.875, P=0.001), and the minimal TFC and IMR that could be obtained with nitroglycerin or ATP administration (r = 0.890, P=0.001). There was also a significant correlation between the proportional improvement in TFC and CFR before and after nitroglycerin injection (r = 0.685, P=0.029). In addition, we observed a lower IMR measured after nitroglycerin than after ATP in three patients, suggesting that CMD may be dominated by NO-sensitive vascular such as prearterioles and that an extensive analysis of the target site of CMD may be achieved by stepwise drug administration. Conclusion Induction of TFC in different states by a stepwise drug approach may serve as a potential primary screening method for coronary microcirculatory dysfunction, thereby reducing the need for further IMR or CFR testing.
Highlights
Coronary microvascular dysfunction (CMD) is a clinical phenomenon that causes myocardial ischemia due to functional or structural abnormalities of the microvascular and is considered one of the causes of nonobstructive coronary heart disease [1]. e invasive diagnostic criteria for CMD mainly include coronary slow flow (CSF) phenomenon presenting as TIMI frame count (TFC) >25 frames, index of microcirculatory resistance (IMR) >25, or coronary flow reserve (CFR)
Due to the huge differences in the complexity of the detection methods, it is worth discussing whether TFC, a relatively easy-toimplement detection method, can replace the complex detection methods of IMR and CFR after its process improvement to achieve the goal of simplifying the CMD assessment process
TFC is the state of CMD at baseline without medication and may contain both functional and structural factors, IMR is the state of maximal hyperemia induced by medication and retains only structural factors, whereas CFR evaluates the effect of medication and corresponds to the weighting of functional factors. erefore, it is not reasonable to directly compare the three parameters and obtain results without correlation in previous studies
Summary
Coronary microvascular dysfunction (CMD) is a clinical phenomenon that causes myocardial ischemia due to functional or structural abnormalities of the microvascular and is considered one of the causes of nonobstructive coronary heart disease [1]. e invasive diagnostic criteria for CMD mainly include coronary slow flow (CSF) phenomenon presenting as TIMI frame count (TFC) >25 frames, index of microcirculatory resistance (IMR) >25, or coronary flow reserve (CFR) 25 frames, index of microcirculatory resistance (IMR) >25, or coronary flow reserve (CFR)
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