Calculation of the Index of Microcirculatory Resistance Without Coronary Wedge Pressure Measurement in the Presence of Epicardial Stenosis

Yong, A.; Layland, Jamie; Fearon, William F.; Ho, Michael; Shah, Maulik; Daniels, David; Whitbourn, Robert; MacIsaac, Andrew; Kritharides, Leonard; Wilson, Andrew; Ng, M.

doi:10.1016/j.jcin.2012.08.019

Cited by 137 publications

(84 citation statements)

References 25 publications

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“…Analyzed FFR data were compared with the original readout values determined by the catheterization laboratory; a consensus reading was agreed on by 2 expert physicians if there were discordant values. In the present study, IMR was calculated as the product of the mean distal coronary pressure during stable hyperemia and mean hyperemic transit time (Tmn) and corrected by using the following formula proposed by Yong et al19: IMR=Pa×Tmn×([1.35×Pd/Pa]–0.32). In the absence of a validated cutoff to identify abnormally increased hyperemic microvascular resistance and the reported variability of IMR in patients with or without coronary heart disease, IMR values ≥75th percentile (28.0) of the present cohort were arbitrarily assumed as high IMR 20, 21.…”

Section: Methodsmentioning

confidence: 99%

Significance of Microvascular Function in Visual—Functional Mismatch Between Invasive Coronary Angiography and Fractional Flow Reserve

Yonetsu

Murai

Kanaji

et al. 2017

JAHA

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BackgroundDespite a moderate correlation between angiographical stenosis and physiological significance, the mechanism of discordance has not been fully elucidated, particularly regarding the significance of microvascular function. This study sought to clarify whether microvascular function affects visual‐functional mismatch between quantitative coronary angiography (QCA) and fractional flow reserve (FFR).Methods and ResultsWe assessed QCA, FFR, coronary flow reserve, and the index of microcirculatory resistance in 849 non‐left‐main coronary lesions with visually estimated intermediate stenoses from 532 patients. Clinical and lesion‐specific characteristics and physiological parameters associated with mismatch and reverse mismatch were studied. Coronary flow reserve and index of microcirculatory resistance showed a weak, but significant, correlation with FFR (R=0.306, P<0.001 and R=0.158, P<0.001, respectively). Four hundred twenty‐two lesions were visually nonsignificant (diameter stenosis assessed by QCA [QCA‐DS] ≤50%) and 427 lesions were visually significant (QCA‐DS >50%). Among visually nonsignificant lesions, FFR ≤0.80 (reverse mismatch) was observed in 129 lesions (30.6%). Among visually significant lesions, FFR >0.80 (mismatch) were observed in 179 lesions (41.9%). The significant predictors of reverse mismatch were male sex, nonculprit lesions of acute coronary syndrome, left anterior descending artery location, smaller QCA reference diameter, greater QCA‐DS, lower coronary flow reserve, and lower index of microcirculatory resistance. Mismatch was associated with right coronary artery location, greater QCA reference diameter, smaller QCA‐DS, lesion length, higher coronary flow reserve, and higher index of microcirculatory resistance.ConclusionsThere was a high prevalence of visual‐functional mismatches between QCA and FFR. The discrepancy was related to clinical characteristics, lesion‐specific factors, and microvascular resistance that was undistinguishable by coronary angiography, thus suggesting the importance of physiological lesion assessment.

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Section: Methodsmentioning

confidence: 99%

Significance of Microvascular Function in Visual—Functional Mismatch Between Invasive Coronary Angiography and Fractional Flow Reserve

Yonetsu

Murai

Kanaji

et al. 2017

JAHA

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“…IMR was calculated as the product of mean distal coronary pressure during stable hyperemia and Tmn hyp . 7 In arteries with FFR<0.75, IMR was corrected for coronary wedge pressure using the method proposed by Yong et al 12 A meticulous technique was followed to avoid potential pitfalls affecting these indices.…”

Section: Intracoronary Physiological Indicesmentioning

confidence: 99%

“…This might lead to overestimation of IMR 36 in tight stenoses with significant collateral support. Even when overestimation should be minimal in intermediate severity stenoses, corrected IMR values as proposed by Yong et al 12 were used to minimize that effect. A separate analysis of our dataset using uncorrected IMR revealed similar results to those reported in the manuscript.…”

Section: Limitationsmentioning

confidence: 99%

Disturbed Coronary Hemodynamics in Vessels With Intermediate Stenoses Evaluated With Fractional Flow Reserve

et al. 2013

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Background— In chronic ischemic heart disease, focal stenosis, diffuse atherosclerotic narrowings, and microcirculatory dysfunction (MCD) contribute to limit myocardial flow. The prevalence of these ischemic heart disease levels in fractional flow reserve (FFR) interrogated vessels remains largely unknown. Methods and Results— Using intracoronary measurements, 91 coronaries (78 patients) with intermediate stenoses were classified in 4 FFR and coronary flow reserve (CFR) agreement groups, using FFR>0.80 and CFR<2 as cutoffs. Index of microcirculatory resistance (IMR) and atherosclerotic burden (Gensini score) were also assessed. MCD was assumed when IMR≥29.1 (75 th percentile). Fifty-four (59.3%) vessels had normal FFR, from which only 20 (37%) presented both normal CFR and IMR. Among vessels with FFR>0.80, most (63%) presented disturbed hemodynamics: abnormal CFR in 28 (52%) and MCD in 18 (33%). Vessels with FFR>0.80 presented higher IMR [adjusted mean 27.6 (95% confidence interval, 23.4–31.8)] than those with FFR≤0.80 [17.3 (95% confidence interval, 13.0–21.7), p=0.001]. Atherosclerotic burden was inversely correlated with CFR ( r =−0.207, P =0.055), and in vessels with FFR>0.80 and CFR<2 (n=28, 39%), IMR had a wide dispersion (7–72.7 U), suggesting a combination of diffuse atherosclerotic narrowings and MCD. Vessels with FFR≤0.80 and normal CFR presented the lowest IMR, suggesting a preserved microcirculation. Conclusions— A substantial number of coronary arteries with stenoses showing an FFR>0.80 present disturbed hemodynamics. Integration of FFR, CFR, and IMR supports the existence of differentiated patterns of ischemic heart disease that combine focal and diffuse coronary narrowings with variable degrees of MCD.

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“…Coronary physiology measurements: Coronary physiology measurements were performed for all intermediate stenoses, as described previously. 8,[14][15][16][17][18][19] All patients received an intravenous bolus injection of 5,000 IU of heparin and intracoronary isosorbide dinitrate (1-2 mg) before angiography. A coronary 0.014-inch pressure-temperature sensor guidewire (Certus, St. Jude Medical, St. Paul, MN, USA) threaded through 5 Fr diagnostic catheters was used for measurements after a diagnostic coronary angiogram (CAG) (Figure 1).…”

Section: Methodsmentioning

confidence: 99%

“…However, IMR calculation is less accurate when FFR myo is 0.45 because P d decreases as FFR myo decreases. 19) This causes an increase in the contribution of P w toward the equation to calculate FFR cor and results in discrepancy between estimated FFR cor as well as IMR. Second, a compensatory mechanism for the regulation of microvascular blood flow may have an effect on the discrepancy, especially in the presence of significant epicardial stenosis.…”

Section: Relationship Between Cmvd and Epicardial Stenosis Severitymentioning

confidence: 99%

Impact of Smoking on Coronary Microcirculatory Resistance in Patients With Coronary Artery Disease

et al. 2015

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SummaryThe aim of this study was to investigate the relationship between coronary microvascular function and smoking using the 3 parameters fractional flow reserve (FFR), coronary flow reserve (CFR thermo ), and index of microcirculatory resistance (IMR) in patients with coronary artery disease (CAD). A total of 97 CAD patients with 148 intermediate stenotic lesions were divided into two groups: current and former smokers (Smokers: n = 54), and those who had never smoked (Non-smokers: n = 43). Coronary physiology measurements were made following coronary angiography at rest and during hyperemia induced with intravenous adenosine triphosphate. If a patient had several intermediate lesions, the lesion producing the largest IMR value and minimum FFR myo and CFR thermo value was selected. Averaged over all patients, the FFR myo , CFR thermo , and IMR values were 0.86 ± 0.10, 2.66 ± 1.50, and 20.8 ± 10.7, respectively. There was no significant correlation between FFR myo and IMR. There were no significant differences between smokers and non-smokers in FFR myo value ( perfusion is dependent on both epicardial and microvascular resistance. 1) An increased microcirculatory resistance indicates the presence of coronary microvascular dysfunction (CMVD), a term introduced to describe abnormalities in the regulation of microvascular blood flow. CMVD has been found to play an important role in determining ischemic threshold 2) and to be independent of epicardial stenosis severity.3) Smoking is known to be associated with the development of epicardial atherosclerosis and impairment of coronary endothelial function. [4][5][6] However, the effects of smoking on coronary microvascular function are unknown.Recently, a parameter called the index of microcirculatory resistance (IMR) was proposed for evaluating coronary microvascular function. The advantage of this parameter is that it could be calculated from values obtained using a coronary temperature and pressure sensing guidewire. 7) IMR has been found to be a reproducible index and to be independent of epicardial stenosis severity.7-10) The aim of this study was to investigate the relationship between microvascular function and smoking in patients with CAD by comparing 3 coronary physiology parameters, fractional flow reserve (FFR), coronary flow reserve (CFR), and IMR, between patients with and without a smoking history. MethodsStudy population: A total of 97 patients with CAD who had 148 discrete intermediate grade stenotic lesions (40-70% diameter stenosis on visual assessment) and visited the Department of Cardiovascular Medicine, Kashiwa Municipal Hospital (Chiba, Japan) from August 2010 to August 2013 were retrospectively enrolled. To examine the relationship between coronary physiology and smoking, patients were divided into two groups based on smoking status; current and former smokers (smokers), and those who had never smoked (non-smokers). The exclusion criteria were 1) history of coronary artery bypass surgery; 2) history of myocardial infarction (MI); 3) recent MI,...

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Calculation of the Index of Microcirculatory Resistance Without Coronary Wedge Pressure Measurement in the Presence of Epicardial Stenosis

Abstract: The FFR(cor), and, by extension, microcirculatory resistance can be derived without the need for P(w). This method enables assessment of coronary microcirculatory status before or without balloon inflation, in the presence of epicardial stenosis.

Cited by 137 publications

References 25 publications

Significance of Microvascular Function in Visual—Functional Mismatch Between Invasive Coronary Angiography and Fractional Flow Reserve

Significance of Microvascular Function in Visual—Functional Mismatch Between Invasive Coronary Angiography and Fractional Flow Reserve

Disturbed Coronary Hemodynamics in Vessels With Intermediate Stenoses Evaluated With Fractional Flow Reserve

Impact of Smoking on Coronary Microcirculatory Resistance in Patients With Coronary Artery Disease

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