Increased Angio-Derived Index of Microcirculatory Resistance Within a Timeframe of 30-60 days After COVID-19 Infection.

BACKGROUND AND OBJECTIVES: Chest pain is a relatively long-term symptom that commonly occurs in patients who have contracted COVID-19. The reasons for these symptoms remain unclear, with coronary microvascular dysfunction (CMD) emerging as a potential factor. This study aimed to assess the presence of CMD in these patients by measuring the angio-derived index of microcirculatory resistance (AMR). METHODS: In this cross-sectional case-control study, patients who had chest pain and a history of COVID-19 infection within the preceding 30 to 60 days were included. The control subjects were patients without COVID-19. Demographic, clinical, and echocardiographic data were recorded. Angiographic images were collected for AMR analysis through an angioplus quantitative flow ratio measurement system. Propensity score matching (PSM) was performed to match the two groups. Multivariate logistic regression was used to examine the association between COVID-19 incidence and the increase in AMR (AMR > 285 mmHg*s/m) after correction for other confounders. RESULTS: After PSM, there were 58 patients in each group (the mean age was 66.3 ± 9.04 years, and 55.2% were men). The average time between the onset of COVID-19 infection and patient presentation at the hospital for coronary angiography was 41 ± 9.5 days. Moreover, there was no significant difference in the quantitative flow ratio between the two groups. Patients with COVID-19 had a greater mean AMR (295 vs. 266, p = 0.002). Multivariate logistic regression analysis revealed that COVID-19 (OR = 3.32, 95% CI = 1.50-7.60, p = 0.004) was significantly associated with an increase in AMR. CONCLUSIONS: Long-term COVID-19 patients who experience chest pain without evidence of myocardial ischemia exhibit an increase in AMR, and CMD may be one of the reasons for this increase. COVID-19 is an independent risk factor for an increase in AMR.

Combined risk estimates of diabetes and coronary angiography-derived index of microcirculatory resistance in patients with non-ST elevation myocardial infarction.

BACKGROUND: Diabetes mellitus (DM) and coronary microvascular dysfunction (CMD) increase the risk of adverse cardiac events in patients with non-ST-segment elevation myocardial infarction (NSTEMI). This study aimed to evaluate the combined risk estimates of DM and CMD, assessed by the angiography-derived index of microcirculatory resistance (angio-IMR), in patients with NSTEMI. METHODS: A total of 2212 patients with NSTEMI who underwent successful percutaneous coronary intervention (PCI) were retrospectively enrolled from three centers. The primary outcome was a composite of cardiac death or readmission for heart failure at a 2-year follow-up. RESULTS: Post-PCI angio-IMR did not significantly differ between the DM group and the non-DM group (20.13 [17.91-22.70] vs. 20.19 [18.14-22.77], P = 0.530). DM patients exhibited a notably higher risk of cardiac death or readmission for heart failure at 2 years compared to non-DM patients (9.5% vs. 5.4%, P < 0.001). NSTEMI patients with both DM and CMD experienced the highest cumulative incidence of cardiac death or readmission for heart failure at 2 years (24.0%, P < 0.001). The combination of DM and CMD in NSTEMI patients were identified as the most powerful independent predictor for cardiac death or readmission for heart failure at 2 years (adjusted HR: 7.894, [95% CI, 4.251-14.659], p < 0.001). CONCLUSIONS: In patients with NSTEMI, the combination of DM and CMD is an independent predictor of cardiac death or readmission for heart failure. Angio-IMR could be used as an additional evaluation tool for the management of NSTEMI patients with DM. TRIAL REGISTRATION: URL: https://www. CLINICALTRIALS: gov ; Unique identifier: NCT05696379.

Prognostic impact of coronary microvascular dysfunction in patients with atrial fibrillation.

BACKGROUND: Coronary microvascular dysfunction (CMD) is frequently observed in atrial fibrillation (AF), the most commonly sustained arrhythmia. Nevertheless, an in-depth prognostic significance of CMD in AF is lacking. We aimed to provide insight into the predictive impact of CMD assessed by a novel non-invasive coronary angiography-derived index of microcirculatory resistance (caIMR) for major adverse events (MACE) in AF patients. METHOD: This study included patients with AF who underwent invasive coronary angiography due to suspected cardiac ischemia and did not exhibit obstructive epicardial coronary artery disease (≤50 % stenosis). The caIMR was prospectively evaluated, and the optimal cutoff value for predicting MACE was determined through ROC analysis. RESULT: A total of 463 patients with AF were enrolled. During a median of 33 months of follow-up, 111 (23.97 %) patients had MACE endpoints. The best caIMR cutoff value was 39.28. In patients with MACE, both the mean caIMR and the prevalence of elevated caIMR (caIMR>39.28) were significantly higher compared to those without MACE. An elevated caIMR was linked to a higher risk of MACE (log-rank P < 0.001) and emerged as an independent predictor of clinical outcomes (HR: 4.029; 95 % CI: 2.529-6.418; P < 0.001). In addition, the risk of MACE was higher in high caIMR patients with non-paroxysmal AF (log-rank P < 0.001) and no catheter ablation (log-rank P < 0.001). CONCLUSION: Elevated caIMR is common and showed a vital independent prognostic significance in AF patients. In addition to well-known risk factors, assessment of microvascular function can be a feasible approach for early prevention and a therapeutic target in AF patients.

Coronary Microvascular Function Assessment using the Coronary Angiography-Derived Index of Microcirculatory Resistance in Patients with ST-segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention.

Background: Studies reporting the status of coronary microvascular function in the infarct-related artery (IRA) after primary percutaneous coronary intervention (PCI) remain limited. This study utilized the coronary angiography-derived index of microcirculatory resistance (caIMR) to assess coronary microvascular function in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary PCI. Methods: We used the FlashAngio system to measure the caIMR after primary PCI in 157 patients with STEMI. The primary endpoint was the occurrence of a major adverse cardiovascular event (MACE), defined as a composite endpoint encompassing cardiac mortality, target vessel revascularization, and rehospitalization due to congestive heart failure (CHF), myocardial infarction (MI), or angina. Results: Approximately 30% of patients diagnosed with STEMI and who experienced successful primary PCI during the study period had a caIMR in the IRA of > 40. The caIMR in the IRA was significantly higher than in the reference vessel (32.9 ± 15.8 vs. 27.4 ± 11.1, p < 0.001). The caIMR in the reference vessel of the caIMR > 40 group was greater than in the caIMR ≤ 40 group (30.9 ± 11.3 vs. 25.9 ± 10.7, p = 0.009). Moreover, the caIMR > 40 group had higher incidence rates of MACEs at 3 months (25.5% vs. 8.3%, p = 0.009) and 1 year (29.8% vs. 13.9%, p = 0.04), than in the caIMR ≤ 40 group, which were mainly driven by a higher rate of rehospitalization due to CHF, MI, or angina. A caIMR in the IRA of > 40 was an independent predictor of a MACE at 3 months (hazard ratio (HR): 3.459, 95% confidence interval (CI): 1.363-8.779, p = 0.009) and 1 year (HR: 2.384, 95% CI: 1.100-5.166, p = 0.03) in patients with STEMI after primary PCI. Conclusions: Patients with STEMI after primary PCI often have coronary microvascular dysfunction, which is indicated by an increased caIMR in the IRA. An elevated caIMR of > 40 in the IRA was associated with an increased risk of adverse outcomes in STEMI patients undergoing primary PCI.

Index of Microcirculatory Resistance to predict microvascular obstruction in STEMI: A systematic review and meta-analysis.

BACKGROUND: Microvascular obstruction (MVO) is an independent predictor of adverse cardiac events after ST-elevation myocardial infarction (STEMI). The Index of Microcirculatory Resistance (IMR) may be a useful marker of MVO, which could simplify the care pathway without the need for Cardiac Magnetic Resonance (CMR). We assessed whether the IMR can predict MVO in STEMI patients. METHODS AND RESULTS: We conducted a systematic review and meta-analysis, including articles where invasive IMR was performed post primary percutaneous coronary intervention (PCI) in addition to MVO assessment with cardiac MRI. We searched PubMed, Scopus, Embase, and Cochrane databases from inception until January 2023. Baseline characteristics, coronary physiology and cardiac MRI data were extracted by two independent reviewers. The random-effects model was used to pool the data. Among 15 articles identified, nine articles (n = 728, mean age 61, 81% male) contained IMR data stratified by MVO. Patients with MVO had a mean IMR of 41.2 [95% CI 32.4-50.4], compared to 25.3 [18.3-32.2] for those without. The difference in IMR between those with and without MVO was 15.1 [9.7-20.6]. Meta-regression analyses demonstrated a linear relationship between IMR and TIMI grade (ß = 0.69 [0.13-1.26]), as well as infarct size (ß = 1.18 [0.24-2.11]) or ejection fraction at 6 months (ß = -0.18 [-0.35 to -0.01]). CONCLUSION: In STEMI, patients with MVO had 15-unit higher IMR than those without. IMR also predicts key prognostic endpoints such as infarct size, MVO, and long-term systolic function.

Quantitative Flow Ratio-Derived Index of Microcirculatory Resistance as a Novel Tool to Identify Microcirculatory Function in Patients with Ischemia and No Obstructive Coronary Artery Disease.

BACKGROUND: Coronary microvascular disease (CMVD) is associated with adverse cardiovascular outcomes. However, there is no reliable and noninvasive quantitative diagnostic method available for CMVD. The use of a pressure wire to measure the index of microcirculatory resistance (IMR) is possible, but it has inevitable practical restrictions. We hypothesized that computation of the quantitative flow ratio could be used to predict CMVD with symptoms of ischemia and no obstructive coronary artery disease (INOCA). METHODS: We retrospectively assessed the diagnostic efficiency of the quantitative flow ratio-derived index of microcirculatory resistance (QMR) in 103 vessels from 66 patients and compared it with invasive IMR using the thermodilution technique. RESULTS: Patients were divided into the CMVD group (41/66, 62.1%) and non-CMVD group (25/66, 37.9%). Pressure wire IMR measurements were made in 103 coronary vessels, including 44 left descending arteries, 18 left circumflex arteries, and 41 right coronary arteries. ROC curve analysis showed a good diagnostic performance of QMR for all arteries (area under the curve = 0.820, 95% confidence interval 0.736-0.904, p < 0.001) in predicting microcirculatory function. The optimal cut-off for QMR to predict microcirculatory function was 266 (sensitivity: 82.9%, specificity: 72.6%, and diagnostic accuracy: 76.7%). CONCLUSION: QMR is a promising tool for the assessment of coronary microcirculation. The assessment of the IMR without the use of a pressure wire may enable more rapid, convenient, and cost-effective assessment of coronary microvascular function.

Comparison of Ticagrelor with Clopidogrel on Coronary Microvascular Dysfunction Following Acute Myocardial Infarction Using Angiography-Derived Index of Microcirculatory Resistance.

PURPOSE: This research aimed to assess the impact of ticagrelor and clopidogrel on coronary microvascular dysfunction (CMD) and prognosis following acute myocardial infarction (AMI), using the angiography-derived index of microcirculatory resistance (angio-IMR) as a non-invasive assessment tool. METHODS: In this retrospective study, angio-IMR was performed to evaluate CMD before and after dual antiplatelet therapy (DAPT) with either ticagrelor (90 mg twice daily, n = 184) or clopidogrel (75 mg once daily, n = 72). The primary endpoint is the improvement of CMD evaluated by angio-IMR (delta angio-IMR) following DAPT. Secondary endpoints included myocardial reinfarction and readmission for heart failure during 2-year follow-up. RESULTS: Compared with clopidogrel, ticagrelor exhibited a significantly higher delta angio-IMR [- 3.09 (5.14) versus - 1.99 (1.91), P = 0.008], indicating a superior improvement of CMD with ticagrelor treatment. Multivariate Cox regression indicated that ticagrelor treatment was related to a reduced risk of readmission for heart failure [8 (4.3) versus 9 (12.5), adjusted HR = 0.329; 95% CI = 0.116-0.934; P = 0.018] and myocardial reinfarction [7 (3.8) versus 8 (11.1), adjusted HR = 0.349; 95% CI = 0.125-0.975; P = 0.026]. Furthermore, ticagrelor treatment serves as an independent predictor of readmission for heart failure (HR = 0.322; 95% CI = 0.110-0.943; P = 0.039). CONCLUSION: The results of this study indicate a potential association between ticagrelor treatment and improved CMD, as well as a reduced risk of cardiovascular events, including myocardial reinfarction and readmission for heart failure in AMI patients. Further randomized controlled trials are necessary to confirm the potential benefits of ticagrelor on CMD and cardiovascular prognosis. This clinical trial was registered in www. CLINICALTRIALS: gov (NCT05978726).

Smoking paradox in coronary function and structure of acute ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention.

BACKGROUND: The Smoking paradox has generated inconsistent findings concerning the clinical prognosis of acute ST-segment elevation myocardial infarction (STEMI) patients, while providing limited insights into coronary anatomy and function which are crucial prognostic factors. Therefore, this study aimed to further investigate the existence of smoking paradox in coronary anatomy and function. METHODS: This study divided STEMI patients into smokers and non-smokers. Quantitative coronary angiography, angiography­derived microcirculatory resistance (AMR) and quantitative flow ratio (QFR) were utilized to analyze coronary anatomy and function. These parameters were compared using multivariable analysis and propensity score matching. The clinical outcomes were evaluated using Kaplan-Meier curve and Cox regression. RESULTS: The study included 1258 patients, with 730 in non-smoker group and 528 in smoker group. Smokers were significantly younger, predominantly male, and had fewer comorbidities. Without adjusting for confounders, smokers exhibited larger lumen diameter [2.03(1.45-2.57) vs. 1.90(1.37-2.49), P = 0.033] and lower AMR [244(212-288) vs. 260(218-301), P = 0.006]. After matching and multivariate adjustment, smokers exhibited inversely smaller lumen diameter [1.97(1.38-2.50) vs. 2.15(1.63-2.60), P = 0.002] and higher incidence of coronary microvascular dysfunction [233(53.9%) vs. 190(43.6%), P = 0.002], but showed similar AMR and clinical outcomes compared to non-smokers. There was no difference in QFR between two groups. CONCLUSION: Smoking among STEMI patients undergoing pPCI was associated with smaller lumen diameter and higher occurrence of coronary microvascular dysfunction, although it had no further impact on clinical prognosis. The smoking paradox observed in coronary anatomy or function may be explained by younger age, gender, and lower prevalence of comorbidities.

[Index of microcirculatory resistance is associated with left ventricular remodeling in patients with acute anterior ST-segment elevation myocardial infarction undergoing emergency primary percutaneous coronary intervention].

OBJECTIVE: To evaluate whether index of microcirculatory resistance (IMR) is associated with left ventricular (LV) remodeling in acute anterior ST elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PPCI). METHODS: This was a single-center retrospective cohort study. The patients with first anterior STEMI who received PPCI from January 2014 to August 2017 in Peking University Third Hospital was enrolled. After PPCI, IMR was measured immediately by using pressure/temperature guidewire. The success rate of IMR measurement was 100%. Also we collected some related clinical data from the medical records and laboratory results. Infarct size [assessed as creatine kinase (CK) peak], echocardiography at baseline and 1 year follow-up were assessed. LV adverse remodeling (LVAR) was defined as ≥20% increase in LV end-diastolic volume (LVEDV). RESULTS: A total of forty-three patients were enrolled, with an average age of (58.7±12.4) years.The patients were divided into two groups as IMR ≤25 and IMR>25 by normal values recommended by previous literature. Compared with IMR ≤25 group, IMR>25 group had a higher percentage of initial thrombolysis in myocardial infraction (TIMI) grade 0 (95.7% vs. 65.0%, P=0.029), higher serum CK peak value [4 090 (383, 15 833)vs. 1 580 (396, 5 583), P=0.004]. The IMR>25 group suffered higher rates of ventricular aneurysm (30.4% vs. 5.0%, P=0.021). There was no difference in LVEDV [(111.0±18.8) mL vs. (115.0±23.6) mL, P=0.503] between the two groups 1 day after MI, but after 1 year, LVEDV in IMR>25 group was significantly higher than in IMR≤25 group [(141.5±33.7) mL vs. (115.9±27.9) mL, P=0.018]. The incidence of LVAR was more significant in IMR>25 group (47.4% vs. 11.8%, P=0.024). Binary Logistics regression showed that IMR [B=0.079, exp(B) (95%CI)=1.082 (1.018－1.149), P=0.011] and serum triglyceride level [B=1.610, exp(B) (95%CI)=5.005 (1.380－18.152), P=0.014] were the predictors of LVAR 1 year after MI. IMR had a good predictive value for LVAR 1 year after MI [area under the curve (AUC)=0.749, P=0.019], IMR>29 was a good cutoff value with sensitivity 81.8% and specificity 68.0%. CONCLUSION: Our study elaborates that immediate measurement of IMR after PPCI in patients with STEMI can reflect the microvascular function.And IMR could be used as a quantitative biomarker to predict LVAR after STEMI.

Implementation of Microcirculation Examination in Clinical Practice-Insights from the Nationwide POL-MKW Registry.

Background and Objectives: The assessment of coronary microcirculation may facilitate risk stratification and treatment adjustment. The aim of this study was to evaluate patients' clinical presentation and treatment following coronary microcirculation assessment, as well as factors associated with an abnormal coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) values. Materials and Results: This retrospective analysis included 223 patients gathered from the national registry of invasive coronary microvascular testing collected between 2018 and 2023. Results: The frequency of coronary microcirculatory assessments in Poland has steadily increased since 2018. Patients with impaired IMR (≥25) were less burdened with comorbidities. Patients with normal IMR underwent revascularisation attempts more frequently (11.9% vs. 29.8%, p = 0.003). After microcirculation testing, calcium channel blockers (CCBs) and angiotensin-converting enzyme inhibitors were added more often for patients with IMR and CFR abnormalities, respectively, as compared to control groups. Moreover, patients with coronary microvascular dysfunction (CMD, defined as CFR and/or IMR abnormality), regardless of treatment choice following microcirculation assessment, were provided with trimetazidine (23.2%) and dihydropyridine CCBs (26.4%) more frequently than those without CMD who were treated conservatively (6.8%) and by revascularisation (4.2% with p = 0.002 and 0% with p < 0.001, respectively). Multivariable analysis revealed no association between angina symptoms and IMR or CFR impairment. Conclusions: The frequency of coronary microcirculatory assessments in Poland has steadily increased. Angina symptoms were not associated with either IMR or CFR impairment. After microcirculation assessment, patients with impaired microcirculation, expressed as either low CFR, high IMR or both, received additional pharmacotherapy treatment more often.