Index Of Microcirculatory Resistance Values Research Articles

Association between index of microcirculatory resistance and patients' characteristics, coronary computed tomography findings, and the sensor location

Abstract Background The index of microcirculatory resistance (IMR) has been widely used for the assessment of microcirculatory function and the detection of the territory with microvascular dysfunction. For measuring coronary physiological indices including IMR, a pressure/temperature sensor-tipped guidewire is recommended to be located distally to the target lesion, however the determinants of IMR including wire location other than the hyperemic microvascular resistance itself are still undetermined. Purpose This study aimed to clarify the determining factors including coronary computed tomography angiography (CCTA) findings, wire position and vessel anatomy and its effect on IMR values. Methods We retrospectively investigated 121 intermediate left anterior descending artery lesions in chronic coronary syndrome patients in our institutional physiological registry (July 2020 to Aug 2022). All patients underwent preprocedural CCTA and coronary physiological assessment with pressure/temperature sensor-tipped guidewire during invasive coronary angiography or percutaneous coronary intervention (PCI). We placed the wire as far distal as practical for the assessment of physiological indices. Under adenosine-induced hyperemia, the wire was pulled manually to the guide catheter and its pullback length was recorded. CCTA assessment included qualitative lesion morphology assessment (spotty calcification, low attenuation plaque, napkin ring sign) and quantitative plaque analysis (remodeling index). Epicardial fat volume is also measured with the proprietary semi-automated software. The predicting factors for IMR was investigated. Result In a total cohort, IMR was 20.40 (14.07-29.92), and the prevalence of IMR>25 was 36 %. On linear regression analysis, patient characteristics including age and gender were not significant predictors for IMR. CCTA-based high risk plaque features (Spotty calcification, low attenuation plaque and napkin ring sign) were also not associated with IMR. In univariable and multivariable linear regression analysis, wire pullback length, remodeling index and epicardial fat volume were significant predictors for IMR (β 1.369 [0.223-2.515, p=0.020, β 6.651 [1.486-11.815], p=0.012, and β 0.055 [0.008-0.103], p=0.023, respectively). Conclusion Wire location (length form the coronary ostium), remodeling index and epicardial fat volume affects IMR values. Caution should be exercised for the interpretation of IMR values in consideration of these factors.

The Index of Microcirculatory Resistance After Primary PCI: A Pooled Analysis of Individual Patient Data

BackgroundDespite treatment with primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI), the risk of heart failure and late death remains high. Microvascular dysfunction, as assessed by the index of microcirculatory resistance (IMR), after primary PCI for STEMI has been associated with worse outcomes. It is unclear whether IMR after primary PCI predicts cardiac death. ObjectivesThe aims of this analysis were: 1) to determine if IMR is an independent predictor of cardiac death; 2) to assess the optimal cutoff value of IMR after STEMI; and 3) to compare IMR with several cardiac magnetic resonance parameters, including infarct size. MethodsIn a collaborative, pooled analysis of individual patient data from 6 cohorts that measured IMR directly after primary PCI, cardiac mortality up to 5 years was estimated using Kaplan-Meier analyses. The primary endpoint was cardiac death using the predefined IMR cutoff value of 40. ResultsIn total, 1,265 patients were included in this study with a median follow-up of 2.8 years (IQR: 1.2-5.0 years). Cardiac death at 5 years occurred in 2.2% and 4.9% of patients (HR: 2.81; 95% CI: 1.34-5.88; P = 0.006) in the IMR ≤40 and IMR >40 groups, respectively. The composite of cardiac death or hospitalization for heart failure occurred in 4.9% and 8.9% (HR: 1.98; 95% CI: 1.20-3.29; P = 0.008) in the IMR ≤40 and IMR >40 groups, respectively. IMR was an independent predictor of cardiac death, whereas coronary flow reserve was not. The optimal cutoff value of IMR for the prediction of cardiac death in this cohort was 70 (HR: 4.73; 95% CI: 2.27-9.83; P < 0.001). Infarct size was 17.6% ± 13.3% and 23.9% ± 14.6% of the left ventricular mass in the IMR ≤40 and IMR >40 groups, respectively (P < 0.001). Microvascular obstruction and intramyocardial hemorrhage occurred more frequently in the IMR >40 group than in the IMR ≤40 group. ConclusionsIn this large, pooled analysis of individual patient data, IMR measured directly after primary PCI in STEMI was an independent predictor of cardiac death. IMR may be used as a tool to identify patients at the time of primary PCI who are at highest risk for late cardiac mortality and who might benefit most from additional cardioprotective therapies and monitoring.

The imPAct of Trimetazidine on MicrOcirculation after Stenting for stable coronary artery disease (PATMOS study).

Myocardial ischemia is caused by epicardial coronary artery stenosis or atherosclerotic disease affecting microcirculation. Trimetazidine (TMZ), promotes glucose oxidation which optimizes cellular energy processes in ischemic conditions. Small studies demonstrated protective effects of TMZ in terms of reducing myocardial injury after percutaneous coronary intervention (PCI), its effect on microcirculation using contemporary investigative methods has not been studied. The aim of the study was to examine effects of trimetazidine, given before elective PCI, on microcirculation using invasively measured index of microcirculatory resistance (IMR). This was prospective, single blinded, randomized study performed in a single university hospital. It included consecutive patients with an indication for PCI of a single, de novo, native coronary artery lesion. Patients were randomly assigned to receive either TMZ plus standard therapy (TMZ group) or just standard therapy. Coronary physiology indices fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) were measured before and after PCI using coronary pressure wire. We randomized 71 patients with similar clinical characteristics and risk profile, previous medications and coronary angiograms. Patientshad similar values of Pd/Pa, FFR and CFR prior to PCI procedure. After PCI, FFR values were higher in TMZ group, while IMR values were lower in this group respectively (FFR TMZ + 0.89 ± 0.05 vs. TMZ - 0.85 ± 0.06, p = 0.007; CFR TMZ + 2.1 ± 0.8 vs. TMZ- 2.3 ± 1.3, p = 0.469; IMR TMZ + 18 ± 9 vs. TMZ- 24 ± 12, p = 0.028). In two-way repeated measures ANOVA PCI was associated with change in FFR values (TMZ p = 0.050; PCI p < 0.001; p for interaction 0.577) and TMZ with change in IMR values (TMZ p = 0.034, PCI p = 0.129, p for interaction 0.344). Adding trimetazidine on top of medical treatment prior to elective PCI reduces microvascular dysfunction by lowering postprocedural IMR values when compared to standard therapy alone.

Four of Five Patients With Chest Pain and Non-Obstructive Coronary Artery Disease who had a Microvascular Assessment had Microvascular Angina

Patients with chest pain and non-obstructive coronary artery disease (NOCAD) may have microvascular disease. Measurement of the index of microcirculatory resistance (IMR) with a coronary pressure wire at the time of invasive coronary angiography identifies those with microvascular disease. This helps to correctly diagnose these patients and tailor their therapeutic strategy. A retrospective audit was undertaken of consecutive patients with NOCAD and measurement of microvascular indices from the Northern region between March 2020 and January 2023 at Auckland City Hospital. Coronary flow reserve, IMR, and fractional flow reserve were measured. Fifty-six participants were included. Seven were excluded as they resided outside the Northern region. Forty-one (75%) were male with mean age of 65 (SD 8.6) years. A total of 47% had a history of smoking, 24% previous myocardial infarction, 7% previous stroke, 51% diabetes; 52% presented with stable angina, 24% with unstable angina and 22% with non-ST elevation myocardial infarction (NSTEMI); 70% were on aspirin, 44% on beta blockers, 18% on calcium channel blockers, 31% nitrates, 38% statins, and 2% nicorandil. Normal IMR (<25) was seen in 24% of patients with an initial diagnosis of stable angina, 15% with unstable angina, and 17% with NSTEMI. Amongst those with chest pain and NOCAD, who had a microvascular assessment, four of five had an elevated IMR, suggesting significant microvascular disease. The remaining patients were reassured that their chest pain was not due to coronary disease. These data reinforce the diagnostic value of IMR in this patient cohort.

Angiography-based index of microcirculatory resistance (AccuIMR) for the assessment of microvascular dysfunction in acute coronary syndrome and chronic coronary syndrome.

To assess the diagnostic accuracy of AccuIMR, a newly proposed, pressure wire-free index, in identifying coronary microvascular dysfunction (CMD) among patients with acute coronary syndrome [including ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI)] and chronic coronary syndrome (CCS). A total of 163 consecutive patients (43 with STEMI, 59 with NSTEMI, and 61 with CCS), who underwent invasive coronary angiography (ICA) and for whom the index of microcirculatory resistance (IMR) was measured, were retrospectively enrolled at a single center. IMR measurements were made in 232 vessels. The AccuIMR based on computational fluid dynamics (CFD) was calculated from coronary angiography. The diagnostic performance of AccuIMR was assessed using wire-based IMR as a reference standard. AccuIMR correlated well with IMR (overall r=0.76, P<0.001; STEMI r=0.78, P<0.001; NSTEMI r=0.78, P<0.001; CCS r=0.75, P<0.001) and had good diagnostic performance in detecting abnormal IMR [overall diagnostic accuracy, sensitivity, and specificity were 94.83% (91.14% to 97.30%), 92.11% (78.62% to 98.34%), and 95.36% (91.38% to 97.86%), respectively]. Using a cutoff value of IMR >40 U for AccuIMR in STEMI and IMR >25 U in NSTEMI and CCS, the area under the receiver operating characteristic (ROC) curve (AUC) of AccuIMR for predicting abnormal IMR value was 0.917 (0.874 to 0.949) in all patients, 1.000 (0.937 to 1.000) in patients with STEMI, 0.941 (0.867 to 0.980) in patients with NSTEMI, and 0.918 (0.841 to 0.966) in patients with CCS. The use of AccuIMR in the evaluation of microvascular diseases could provide valuable information and potentially increase the application of physiological assessment for microcirculation in patients with ischemic heart disease.

One-year results from the Assessing MICRO-vascular resistances via IMR to predict outcome in ST-elevation myocardial infarction patients with multivessel disease undergoing primary PCI (AMICRO) trial.

In ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary angioplasty (PPCI) the index of microcirculatory resistance (IMR) correlates to the extent of myocardial damage and left ventricular (LV) function recovery. Data on the IMR time-course and impact on clinical outcome in STEMI patients with multi-vessel disease (MVD) are scarce. We designed a prospective, multicenter clinical trial to assess the infarct-related artery (IRA)-IMR in STEMI patients with MVD undergoing PPCI and to explore its potential in relationship with outcome and LV remodeling. The study enrolled 242 STEMI patients with MVD. Both fractional flow reserve (FFR) and IMR of the IRA were assessed after successful PPCI. Then, FFR/IMR measurements were repeated in the IRA at a staged angiography, and FFR-guided angioplasty was performed in non-IRA lesions. The primary endpoint was the composite of cardiovascular death, re-infarction, re-hospitalization for heart failure, resuscitation or appropriate ICD shock at 1-year follow-up. A significant improvement of IRA-IMR values (from 47.9 to 34.2, p < 0.0001) was observed early after PPCI. Staged FFR-guided angioplasty was performed in 102 non-IRA lesions. We failed to find a correlation between IRA-IMR, clinical events and LV remodeling. Notwithstanding, in patients with anterior STEMI an inverse correlation between initial IMR values and LV function at follow-up was observed. After successful PPCI, a significant proportion of patients with STEMI and MVD had coronary microvascular dysfunction as assessed by IMR that recovered early after reperfusion. Higher IMR values predicted lack of improvement of LV function only in anterior STEMI. https://clinicaltrials.gov/, identifier [NCT02325973].

The diagnostic value of left-anterior-descending artery velocity assessed by transthoracic Doppler echocardiography for microvascular dysfunction in stenotic left-anterior-descending artery

Abstract Background Index of microcirculatory resistance (IMR) has been used as a clinical measure of microvascular function. Transthoracic Doppler echocardiography (TDE) can provide information on the functional status of coronary artery circulation. This study aims to assess the diagnostic value of left-anterior-descending artery (LAD) flow velocity by TDE for microvascular dysfunction. Methods Consecutive patients who were scheduled for elective percutaneous coronary intervention (PCI) for LAD lesions were prospectively enrolled in the single tertiary-care center between April 2020 and July 2021. Pre-PCI LAD diastolic peak velocity (DPV) by TDE at rest and hyperemia were measured. By invasive coronary angiography, quantitative coronary angiography and invasive wire-based physiological indices including fractional flow reserve (FFR) and index of microcirculatory resistance (IMR) were measured. Results A total of 104 patients were studied. Median FFR and IMR values were 0.70 (0.60–0.74) and 20.68 (14.92–31.69), respectively. No significant relationship was observed between FFR and IMR. The prevalence of microvascular dysfunction defined as IMR≥25 was 39.4%. Basal DPV was 25 (20–33) cm/sec, and hyperemic DPV was 51 (41–67) cm/sec. In lesions with IMR≥25, reference diameter (RD) was significantly greater [2.63 (2.22–3.19) mm vs 2.39 (2.09–2.66) mm, p=0.019], basal DPV was lower [26 (18–29) cm/sec vs 29 (22–37) cm/sec, p=0.022)] and hyperemic DPV was lower [49 (19–54) cm/sec vs 56 (42–70) cm/sec, p=0.023] compared to lesions with IMR&amp;lt;25. ROC analysis showed basal DPV and RD are significant predictors of IMR≥25 [basal DPV: AUC 0.633 (0.525–0.742), best cutoff 29cm/sec RD: AUC 0.636 (0.523–0.750), best cutoff 2.84mm]. Multivariable logistic regression analysis showed basal DPV&amp;lt;29cm/sec and RD&amp;gt;2.84mm are independent predictors for IMR≥25 [Odds ratio: 3.08 (1.22–7.78), p=0.017; odds ratio 4.40 (1.55–12.50), p=0.005]. Conclusion Basal DPV by non-invasive pre-PCI TDE and reference diameter can predict lesions with coexisting microvascular dysfunction in LAD territory with functionally significant lesions without the need of vasodilator-induced hyperemia and a wire-based invasive physiological measurement. Funding Acknowledgement Type of funding sources: None.

The application of myocardial contrast echocardiography in assessing microcirculation perfusion in patients with acute myocardial infarction after PCI

BackgroundTo evaluate the myocardial microcirculation perfusion of patients with acute ST-segment elevation myocardial infarction (STEMI) with a different index of microcirculatory resistance (IMR) after percutaneous coronary intervention (PCI) by myocardial contrast echocardiography (MCE) and analyse the value of MCE in predicting myocardial perfusion after PCI.MethodsFifty-six patients with acute STEMI who underwent an emergency PCI were selected from October 2018 to October 2019 in our hospital. According to the IMR values measured during PCI treatment, the patients were divided into three groups. Traditional ultrasound and MCE were performed one week after PCI. The left ventricular ejection fraction (LVEF), ventricular wall motion score index (WMSI), A value, β value and A × β value (which refers to the patient’s myocardial blood flow) were measured. The receiver operating characteristic curve was drawn to evaluate the effectiveness of the MCE parameters in the diagnosis of myocardial microcirculation perfusion disorders.ResultsThe results showed that there was no significant difference in the LVEF among the groups. The WMSI in Group 3 was statistically different from that in Groups 1 and 2 (P < 0.05), but there was no statistically significant difference in the WMSI between Groups 1 and 2. Among the three groups, the A value, β value and A × β value were significantly different (P < 0.05). According to Spearman’s correlation analysis, the MCE quantitative parameters (i.e. the A value, β value and A × β value) were negatively correlated with the IMR value (r = −0.523, −0.471, −0.577, P < 0.01).ConclusionsThe A value, β value and A × β value were negatively correlated with the IMR value. Furthermore, MCE could be used to observe the myocardial perfusion in patients with acute STEMI after PCI and may be one of the indicators used to accurately evaluate myocardial microcirculation.

Abstract 10954: Quantification of Myocardial Perfusion Reserve Using a Cardiac-Centered Camera: First Comparison with Invasive Indexes of Coronary Microvascular Disease

Introduction: – The invasive quantification of coronary flow reserve (CFR), the index of microcirculatory resistance (IMR), and fractional flow reserve (FFR) allows to assess coronary physiology. Although semi-conductor (CZT) SPECT myocardial perfusion reserve (MPR) has been previously compared with FFR, there are no data documenting the relationships between CZT SPECT MPR on one hand and CFR and/or IMR on the other hand. We assessed the performances of noninvasive CZT SPECT MPR in comparison with invasively determined FFR, CFR, and IMR. Methods: – Rest and dipyridamole-induced stress myocardial blood flow and MPR were quantified using 99m Tc-SestaMIBI and a Discovery NM 530c camera in 26 patients with suspected or known coronary artery disease who underwent conventional invasive coronary angiography. Thermodilution-derived resting and adenosine-induced hyperemic mean transit times, distal intracoronary pressures, and mean aortic pressures were assessed for the quantification of FFR, CFR, and IMR values. Results: – Only 2/35 vessels presented with a pathological (&lt;0.8) FFR. A moderate yet significant correlation was observed between regional CZT SPECT MPR and CFR (r=0.40, P =.02). The sensitivity, specificity, positive and negative predictive value, and accuracy of regional CZT SPECT MPR vs CFR were 69% [44-86%], 94% [74-100%], 91% [65-100%], 77% [56-90%], and 82% [65-93%], respectively. In territories without underlying CAD (n=32), CZT SPECT MPR values were significantly higher in those with CFR≥2 and IMR&lt;25 (negative composite criterion, n=14) than in those with CFR&lt;2 and IMR≥25 (positive composite criterion, n=8, CZT SPECT MPR, 2.6 [2.1-3.6] vs 1.6 [1.2-1.8]), P &lt;.01). Regional CZT SPECT MPR displayed sensitivity, specificity, positive and negative predictive value, and accuracy of 87% [53-99%], 100% [78-100%], 100% [64-100%], 93% [70-99%], and 95% [77-99%] for the diagnosis of a positive composite criterion, respectively. Conclusions: – CZT SPECT MPR presented a moderate, significant correlation with thermodilution CFR and good diagnostic performances for the detection of patients at high risk of cardiovascular events (low CFR and high IMR) in the absence of obstructive CAD.

Coronary Microcirculatory Dysfunction and Acute Cellular Rejection After Heart Transplantation.

Acute cellular rejection is a major determinant of mortality and retransplantation after heart transplantation. We sought to evaluate the prognostic implications of coronary microcirculatory dysfunction assessed by index of microcirculatory resistance (IMR) for the risk of acute cellular rejection after heart transplantation. The present study prospectively enrolled 154 heart transplant recipients who underwent scheduled coronary angiography and invasive coronary physiological assessment 1 month after transplantation. IMR is microcirculatory resistance under maximal hyperemia. By measuring hyperemic mean transit time using 3 injections (4 mL each) of room-temperature saline under maximal hyperemia, IMR was calculated as hyperemic distal coronary pressure×hyperemic mean transit time. The primary end point was biopsy-proven acute cellular rejection of grade ≥2R during 2 years of follow-up after transplantation and was compared by using multivariable Cox proportional hazards regression according to IMR. The incremental prognostic value of IMR, in addition to the model with clinical factors, was evaluated by comparison of C-index, net reclassification index, and integrated discrimination index. The mean age of recipients was 51.2±13.1 years (81.2% male), and the cumulative incidence of acute cellular rejection was 19.0% at 2 years. Patients with acute cellular rejection had significantly higher IMR values at 1 month than those without acute cellular rejection (23.1±8.6 versus 16.8±11.1, P=0.002). IMR was significantly associated with the risk of acute cellular rejection (per 5-U increase: adjusted hazard ratio, 1.18 [95% CI, 1.04-1.34], P=0.011) and the optimal cutoff value of IMR to predict acute cellular rejection was 15. Patients with IMR≥15 showed significantly higher risk of acute cellular rejection than those with IMR<15 (34.4% versus 3.8%; adjusted hazard ratio, 15.3 [95% CI 3.6-65.7], P<0.001). Addition of IMR to clinical variables showed significantly higher discriminant and reclassification ability for risk of acute cellular rejection (C-index 0.87 versus 0.74, P<0.001; net reclassification index 1.05, P<0.001; integrated discrimination index 0.20, P<0.001). Coronary microcirculatory dysfunction assessed by IMR measured early after heart transplantation showed significant association with the risk of acute cellular rejection. In addition to surveillance endomyocardial biopsy, early stratification using IMR could be a clinically useful tool to identify patients at higher risk of future acute cellular rejection after heart transplantation. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02798731.

Characteristic findings of microvascular dysfunction on coronary computed tomography angiography in patients with intermediate coronary stenosis.

We aimed to assess the prevalence of coexistence of coronary microvascular dysfunction (CMD) in patients with intermediate epicardial stenosis and to explore coronary computed tomography angiography (CCTA)-derived lesion-, vessel-, and cardiac fat-related characteristic findings associated with CMD. A retrospective cross-sectional single-center study included a total of 177 patients with intermediate stenosis in the left anterior descending artery (LAD) who underwent CCTA and invasive physiological measurements. The 320-slice CCTA analysis included qualitative and quantitative assessments ofplaque, vessel, epicardial fat volume (ECFV) and epicardial fat attenuation (ECFA), and pericoronary fat attenuation (FAI). CMD was defined by the index of microcirculatory resistance (IMR) ≥ 25. In the entire cohort, median fractional flow reserve (FFR) and median IMR values were 0.77 (0.69-0.84) and 19.0 (13.7-27.7), respectively. The prevalence of CMD was 32.8 % (58/177) in the total cohort. The coexistence of CMD and functionally significant stenosis was 34.3 % (37/108), whereas CMD in nonsignificant intermediate stenosis was 30.4 % (21/69). CMD was significantly associated with greater lumen volume (p = 0.031), greater fibrofatty and necrotic component (FFNC) volume (p = 0.030), and greater ECFV (p = 0.030), but not with FAI (p = 0.832) and ECFA (p = 0.445). On multivariable logistic regression analysis, vessel volume, vessel lumen volume, lesion remodeling index, ECFV, and lesion FFNC volume were independent predictors of CMD. The prevalence of CMD was about one-third in patients with intermediate stenosis in LAD regardless of the presence or absence of functional stenosis significance. The integrated CCTA assessment may help in the identification of CMD. • The coexistence of coronary microvascular dysfunction (CMD) and functionally significant stenosis was 34.3 %, whereas CMD in nonsignificant intermediate stenosis was 30.4 %. • Coronary computed tomography angiography (CCTA)-derived CMD characteristics were vessel volume, vessel lumen volume, remodeling index, epicardial fat volume, and fibrofatty necrotic core volume. • Integrated CCTA assessment may help identify the coexistence of CMD and epicardial stenosis.

The Comparison between Two Risk Scores as for the Prediction of Coronary Microvascular Obstruction during Primary Percutaneous Intervention.

ResumoFundamento:Para pacientes com infarto do miocárdio com elevação do segmento ST (IAMCST) que sofrem de obstrução coronariana microvascular funcional e estrutural (OCM) subsequente, nenhuma abordagem terapêutica específica e definitiva de atenuação foi comprovada como válida em testes de larga escala atuais, o que destaca a necessidade de abordar seu reconhecimento precoce.Objetivos:Este estudo teve como objetivo comparar o desempenho de dois escores de risco clínico com uma medida objetiva de OCM durante intervenção coronária percutânea (ICP) em casos de IAMCSTMétodos:A medição do índice de resistência microcirculatória (IRM) foi realizada e os parâmetros clínicos e angiográficos basais também foram registrados. Os pacientes foram divididos em entre os grupos OM (obstrução microvascular) e NOM (não-obstrução microvascular), de acordo com o valor de IRM pós-procedimento. O risco de OCM foi avaliado para todos os participantes pelos escores preditivos SAK e ATI, respectivamente. Cada sistema foi calculado somando-se as pontuações de todas as variáveis. As curvas de características do operador receptor (ROC) e a área sob a curva (AUC) de dois modelos de risco foram utilizadas para avaliar o desempenho discriminatório. Um ecocardiograma foi realizado sete dias após o procedimento para avaliar a fração de ejeção do ventrículo esquerdo (FEVE). Um valor P bicaudal de <0,05 foi considerado estatisticamente significativo.Resultados:Entre os 65 pacientes elegíveis com IAMCST, 48 foram alocados no grupo NOM e 17 no grupo OM, com uma incidência de OCM de 26,15%. Não houve diferença significativa na AUC entre os dois escores. A FEVE avaliada para o grupo NOM foi maior do que para o grupo OM.Conclusão:Os escores SAK e ATI tiveram bom desempenho para estimar o risco de OCM após ICP primário para pacientes com IAMCST.

Size of low wall shear stress areas in coronary arteries is related to epicardial physiology and not to microcirculatory resistance

Abstract Background Wall shear stress (WSS) plays an important role in coronary atherosclerosis. Low WSS is associated with inflammation, endothelial dysfunction, and progression of atherosclerosis; while high WSS leads to vulnerable plaque transformation and future myocardial infarction. Defining the relationship between WSS and the currently available coronary physiology indices would provide valuable insights into potential mechanisms for predicting future adverse cardiac events. Purpose To investigate the relationship between WSS and the coronary epicardial/microvascular physiology indices. Methods Patients undergoing coronary angiography and physiology testing were prospectively recruited. Physiology measurements were performed under resting and hyperaemic conditions using a pressure/temperature sensor guidewire. Fractional flow reserve (FFR), non-hyperaemic pressure ratios (NHPRs), coronary flow reserve (CFR), and corrected index of microcirculatory resistance (IMR) were measured. The NHPRs including resting full-cycle ratio (RFR), resting distal/aortic pressure (Pd/Pa), instantaneous wave-free ratio (iFR), diastolic pressure ratio (dPR) and diastolic hyperaemia-free ratio (DFR) were derived offline by a blinded expert reader. Values of FFR ≤0.80, NHPR ≤0.89, CFR &amp;lt;2, or IMR &amp;gt;25 were considered ischaemic/abnormal. Computational fluid dynamics analysis was performed and fluid motion equations were solved using finite-volume based software. The inlet and outlet boundary conditions were set to the patient-specific Pa and Pd respectively. The lesion WSS, mean WSS in five segments (WSSupstream = 5mm proximal to lesion, WSSprox = proximal third of lesion, WSSmid = middle third of lesion, WSSdistal = distal third of lesion, WSSdownstream = 5mm distal to lesion), and the total area of low WSS (defined as &amp;lt;1 Pa) along the entire vessel were calculated (Figure A). Results A total of 112 vessels from 93 patients were included in the study. The total area of low WSS was significantly larger in lesions with ischaemic FFR, NHPRs, and CFR values (Figure B), and not significantly different in lesions with abnormal IMR values. There was no significant difference in lesion WSS between groups stratified by all physiology indices. Within the lesion WSS sub-segments, WSSprox was significant higher in ischaemic lesions stratified by normal/abnormal FFR, iFR, and dPR (4.2 vs 3.3 Pa, 4.2 vs 3.3 Pa, 4.3 vs 3.3 Pa respectively, all p=0.04), and not significantly different when stratified by RFR, DFR, Pd/Pa, CFR, and IMR. Conclusion Functionally significant coronary lesions classified by the epicardial physiology indices have significantly larger total area of low WSS and higher WSSprox which may explain the higher cardiovascular event rates in patients with ischaemic lesions. There was no significant relationship between WSS and coronary microcirculatory resistance. Figure 1 Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National Heart Foundation of Australia Health Professional Scholarship

Mechanical and Pharmacological Revascularization Strategies for Prevention of Microvascular Dysfunction in ST-Segment Elevation Myocardial Infarction: Analysis from Index of Microcirculatory Resistance Registry Data.

Objectives We aimed to identify mechanical and pharmacological revascularization strategies correlated with the index of microcirculatory resistance (IMR) in ST-elevation myocardial infarction (STEMI) patients. Background Microvascular dysfunction (MVD) after STEMI is correlated with infarct size and poor long-term prognosis, and the IMR is a useful analytical method for the quantitative assessment of MVD. However, therapeutic strategies that can reliably reduce MVD remain uncertain. Methods Patients with STEMI who underwent primary percutaneous coronary intervention (PCI) were enrolled. The IMR was measured with a pressure sensor/thermistor-tipped guidewire immediately after primary PCI. High IMR was defined as values ≥66th percentile of IMR in enrolled patients (IMR > 30.9 IU). Results A total of 160 STEMI patients were analyzed (high IMR = 54 patients). Clinical factors for Killip class (P=0.006), delayed hospitalization from symptom onset (P=0.004), peak troponin-I level (P=0.042), and multivessel disease (P=0.003) were associated with high IMR. Achieving final thrombolysis in myocardial infarction myocardial perfusion grade 3 tended to be associated with low IMR (P=0.119), whereas the presence of distal embolization was significantly associated with high IMR (P=0.034). In terms of therapeutic strategies that involved adjusting clinical and angiographic factors associated with IMR, preloading of third-generation P2Y12 inhibitors correlated with reducing IMR value (β = −10.30, P < 0.001). Mechanical therapeutic strategies including stent diameter/length, preballoon dilatation, direct stenting, and thrombectomy were not associated with low IMR value (all P > 0.05), and postballoon dilatation was associated with high IMR (β = 8.30, P=0.020). Conclusions In our study, mechanical strategies were suboptimal in achieving myocardial salvage. Preloading of third-generation P2Y12 inhibitors revealed decreased IMR value, indicative of MVD prevention.

NEUTROPHIL-LYMPHOCYTE RATIO AND PLATELET-LYMPHOCYTE RATIO AS PREDICTORS OF CORONARY MICROCIRCULATORY DISEASE OCCURRENCE AND OUTCOME IN PATIENTS WITH CHRONIC CORONARY SYNDROME AND NO SIGNIFICANT CORONARY ARTERY STENOSIS

Introduction: Index of microcirculatory resistance assessment is an invasive method of measuring coronary microcirculation function. Association between impaired microcirculatory function and higher rate of cardiovascular events was proven. Neutrophil-lymphocyte ratio and platelet-lymphocyte ratio seem to be a promising parameters to predict coronary microcirculatory disease in patients with chronic coronary syndrome. The aim: To determine neutrophil-lymphocyte ratio and platelet-lymphocyte ratio levels in patients with coronary microcirculatory disease and potential association with clinical outcome. Material and methods: 82 consecutive patients with mean age of 67 years, 67% male, were tested for presence of coronary microcirculatory disease using index of microcirculatory resistance. Neutrophil-lymphocyte ratio and platelet-lymphocyte ratio were calculated based on admission full blood count. Follow-up with major adverse cardiac and cardiovascular events registration was performed (median 24 months). Results: The study showed significantly higher neutrophil-lymphocyte ratio and platelet-lymphocyte ratio in patients with coronary microcirculatory disease compared to control group (3.58±2.61 vs 2.54±1.09 and 164±87.9 vs 124±36.6 respectively). Higher level of platelet-lymphocyte ratio in patients with coronary microcirculatory disease results in worse MACCE-free survival. Optimal cut-off values of neutrophil-lymphocyte ratio and platelet-lymphocyte ratio to detect coronary microcirculatory disease were 3.2 and 181.3, respectively. Conclusions: Higher neutrophil-lymphocyte ratio and platelet-lymphocyte ratio are associated with increased index of microcirculatory resistance value. Platelet-lymphocyte ratio may be used as a predictor of worse outcome in patients with coronary microcirculatory disease.

Functional classification discordance in intermediate coronary stenoses between fractional flow reserve and angiography-based quantitative flow ratio

BackgroundMeasurement of the contrast-flow quantitative flow ratio (cQFR) is a novel method for rapid computational estimation of fractional flow reserve (FFR). Discordance between FFR and cQFR has not been completely...

Coronary Functional Abnormalities in Patients With Angina and Nonobstructive Coronary Artery Disease

BackgroundApproximately one-half of patients undergoing diagnostic coronary angiography for angina have no significant coronary stenosis, in whom coronary functional abnormalities could be involved. ObjectivesThis study examined the significance of coronary functional abnormalities in a comprehensive manner for both epicardial and microvascular coronary arteries in patients with angina and nonobstructive coronary artery disease (CAD). MethodsThis study prospectively enrolled 187 consecutive patients (male/female 113/74, 63.2 ± 12.3 years), who underwent acetylcholine provocation test for coronary spasm and measurement of index of microcirculatory resistance (IMR) to evaluate coronary microvascular function, and followed them for a median of 893 days. ResultsOf all subjects, acetylcholine test identified 128 patients with vasospastic angina (VSA) (68%), and cardiac events occurred in 10 patients (5.3%) during the follow-up. Multivariable analysis revealed that IMR correlated with the incidence of cardiac events (hazard ratio: 1.05; 95% confidence interval: 1.02 to 1.09; p = 0.002) and receiver-operating characteristics (ROC) curve analysis identified IMR of 18.0 as the optimal cut-off value. Among the 4 groups based on the cut-off value of IMR and the presence of VSA, the Kaplan-Meier survival analysis showed a significantly worse prognosis in the group with high IMR (≥18.0) and VSA compared with other groups (log rank, p = 0.002). Importantly, intracoronary administration of fasudil, a Rho-kinase inhibitor, significantly ameliorated IMR in the VSA patients with increased IMR (p < 0.0001). ConclusionsThese results indicate that in patients with angina and nonobstructive CAD, coexistence of epicardial coronary spasm and increased microvascular resistance is associated with worse prognosis, for which Rho-kinase activation may be involved.

Feasibility, safety and effectiveness in measuring microvascular resistance with regadenoson.

AIMThe study aims to test whether simultaneous measurement of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) is feasible, safe and effective during regadenoson-induced hyperemia.METHODS AND RESULTSFFR, CFR and IMR were measured simultaneously during regadenoson (Rapiscan 400 μg) -induced hyperemia in 50 patients with stable coronary artery disease with a SYNTAX score of <22. Simultaneous measurement of FFR, CFR and IMR was technically feasible in all cases (50/50). No side effects occurred and even patients fulfilling classical contraindications for the use of adenosine (10/50) could be included. Regadenoson-induced hyperemia remained stable after maximal pressure drop for more than 35 sec as measured by systemic aortic and distal coronary pressure. There was a significant drop in transit mean time from baseline to hyperemia of more than 50% (1.0 ± 0.6 s vs. 0.4 ± 0.2 s, p < 0.01). Patients' mean IMR value was 23.4, and IMR values above 75th percentile significantly correlated with metformin demanding diabetes mellitus with OR 21.76 and nicotine abuse with OR 10.28.CONCLUSIONA single intravenous regadenoson bolus via peripheral line increases coronary blood flow without harmful systemic side effects enabling interventionists to simultaneously assess FFR, CFR and IMR in patients with stable coronary artery disease.

Combined Primary PCI with Multiple Thrombus Burden Reduction Therapy Improved Cardiac Function in Patients with Acute Anterior Myocardial Infarction.

High thrombus burden induced slow-flow and no-reflow during primary percutaneous coronary intervention (PCI) and is associated with a poor prognosis. We aimed to investigate whether a combined thrombus burden reduction therapy during primary PCI, could improve microcirculation and enhance cardiac function in the long-term.Anterior wall STEMI patients with high thrombus burden were randomly assigned to receive a combined thrombus burden reduction therapy or thrombus aspiration alone. The primary end points included the percentage of patients with TMPG (TIMI myocardial perfusion grade) 3, STR (ST-segment resolution) above 70%, the index of microcirculatory resistance (IMR) and left ventricular ejection fraction (LVEF) difference.Twenty-two patients in the combined interventional group and 24 in the control group completed 1-year follow-up. The percentages of patients with TMPG 3 (68.2% versus 33.3%, P = 0.006) and STR above 70% (63.6% versus 25%, P = 0.016) were significantly higher in the combined group. IMR was significantly lower in the combined interventional group (31.50 ± 13.39 U versus 62.72 ± 22.80 U, P = 0.002). At 3 months and 1 year, the overall LVEF value was better in the combined interventional group (42.1% versus 40.0%, P = 0.049; 41.9% versus 39.8%, P = 0.042), respectively. The IMR value was negatively correlated with the EF value at 3 months (r = -0.145, P = 0.013) and 1 year (r = -0.333, P = 0.031).A combined thrombus burden reduction therapy during primary PCI can safely reduce thrombus burden, improve myocardial tissue perfusion, and improve cardiac function among STEMI patients with high thrombus burden. IMR might be a good predictor for post-myocardial infarction cardiac function.

Optical Coherence Tomography–Defined Plaque Vulnerability in Relation to Functional Stenosis Severity and Microvascular Dysfunction

ObjectivesThis study sought to investigate the relationship of unstable plaque features with physiological lesion severity and microvascular dysfunction. BackgroundThe functional severity of epicardial lesions and microvascular dysfunction are both related to adverse clinical outcomes. MethodsWe investigated 382 de novo intermediate and severe coronary lesions in 340 patients who underwent optical coherence tomography, fractional flow reserve (FFR), and index of microcirculatory resistance (IMR) examinations. Lesions were divided into tertiles based on either FFR or IMR values. The optical coherence tomography findings were compared among the tertiles of FFR and IMR. Each tertile was defined as follows: FFR-T1 (FFR <0.74), FFR-T2 (0.74 ≤ FFR ≤0.81), and FFR-T3 (FFR >0.81); and IMR-T1 (IMR ≥25), IMR-T2 (15 < IMR <25), and IMR-T3 (IMR ≤15). ResultsNo significant relationship was observed between FFR and IMR. The prevalence of optical coherence tomography–defined thin-cap fibroatheroma (TCFA) was significantly greater in IMR-T1 than in IMR-T2 and IMR-T3. An overall significant difference in the prevalence of TCFAs was detected among FFR tertiles, although no pairwise comparison revealed statistical significance. The prevalence of ruptured plaque was significantly greater in IMR-T1 than in IMR-T2 and IMR-T3, although no significant difference was observed between FFR tertiles. Multivariate analysis showed that FFR and IMR were independent predictors of the prevalence of TCFAs (odds ratio: 0.036; 95% confidence interval: 0.004 to 0342; p = 0.004; and odds ratio: 1.034; 95% confidence interval: 1.014 to 1.054; p = 0.001, respectively). ConclusionsLower FFR and higher IMR values were independent predictors of the presence of a TCFA in angiographically intermediate-to-severe stable lesions or nonculprit lesions in acute coronary syndrome.