Prognostic value of the index of microcirculatory resistance after percutaneous coronary intervention in patients with non-ST-segment elevation acute coronary syndrome

Phenotyping the Use of Cangrelor in Percutaneous Coronary Interventions

The use of antiplatelet agents is essential in percutaneous coronary interventions, both periprocedurally and in the post-interventional period. Procedural antiplatelet therapy, aiming to limit ischemic complications, is mostly administered with oral agents, including aspirin and P2Y12 inhibitors. However, there are several limitations in the use of oral P2Y12 inhibitors, including their difficult administration in patients presenting with cardiogenic shock and their relatively slower onset of action, leaving a significant period of the procedure with a suboptimal antiplatelet effect. These pitfalls could be avoided with the use of cangrelor, the only available intravenous P2Y12 inhibitor, which has a rapid onset and offset antiplatelet effect, as well as a favorable pharmacological profile. The use of cangrelor has been increasing in recent years, with several studies aiming to determine what the optimal patient phenotype to receive such treatment ultimately is and how its use could be adjunctive to oral P2Y12 inhibitors. Therefore, the aim of this review is to provide an overview of the pharmacological profile of cangrelor and an update regarding the clinical evidence supporting its use, as well as to discuss the optimal patient phenotype, related clinical algorithms, and future implications for larger implementation of this agent into everyday clinical practice.

FFR, iFR, CFR, and IMR: Results from clinical trials

In this review article, we provide an overview of the definition and application of fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), coronary flow reserve (CFR), and index of microvascular resistance (IMR) in the diagnosis, prognosis, and management of coronary microvascular dysfunction. We discuss their respective limitations as it relates to microvascular dysfunction. In each section, we review the most recent evidence supporting their use in microvascular and epicardial coronary artery disease. We also highlight specific clinical conditions with emerging indications for the use of these indices, including in the setting of microvascular dysfunction due to acute myocardial infarction, heart failure with preserved ejection fraction, and post-cardiac transplant.

Invasive assessment of coronary microvascular dysfunction and cardiovascular outcomes across the full spectrum of CHD: a meta-analysis

INTRODUCTION AND OBJECTIVES

Coronary microvascular dysfunction (CMD) is highly prevalent and is recognized as an important clinical entity in patients with coronary heart disease (CHD). Nevertheless, the association of CMD with adverse cardiovascular events in the spectrum of CHD has not been systemically quantified.

METHODS

We searched electronic databases for studies on patients with CHD in whom coronary microvascular function was measured invasively, and clinical events were recorded. The primary endpoint was major adverse cardiac events (MACE), and the secondary endpoint was all-cause death. Estimates of effect were calculated using a random-effects model from published risk ratios.

RESULTS

We included 27 studies with 11 404 patients. Patients with CMD assessed by invasive methods had a higher risk of MACE (RR, 2.18; 95%CI, 1.80-2.64; P<.01) and all-cause death (RR, 1.88; 95%CI, 1.55-2.27; P<.01) than those without CMD. There was no significant difference in the impact of CMD on MACE (interaction P value=.95) among different invasive measurement modalities. The magnitude of risk of CMD assessed by invasive measurements for MACE was greater in acute coronary syndrome patients (RR, 2.84, 95%CI, 2.26-3.57; P<.01) than in chronic coronary syndrome patients (RR, 1.77, 95%CI, 1.44-2.18; P<.01) (interaction P value<.01).

CONCLUSIONS

CMD based on invasive measurements was associated with a high incidence of MACE and all-cause death in patients with CHD. The magnitude of risk for cardiovascular events in CMD as assessed by invasive measurements was similar among different methods but varied among CHD populations.

CVIT expert consensus document on primary percutaneous coronary intervention (PCI) for acute coronary syndromes (ACS) in 2024

Primary Percutaneous Coronary Intervention (PCI) has significantly contributed to reducing the mortality of patients with ST-segment elevation myocardial infarction (STEMI) even in cardiogenic shock and is now the standard of care in most of Japanese institutions. The Task Force on Primary PCI of the Japanese Association of Cardiovascular Intervention and Therapeutics (CVIT) proposed an expert consensus document for the management of acute myocardial infarction (AMI) focusing on procedural aspects of primary PCI in 2018 and updated in 2022. Recently, the European Society of Cardiology (ESC) published the guidelines for the management of acute coronary syndrome in 2023. Major new updates in the 2023 ESC guideline include: (1) intravascular imaging should be considered to guide PCI (Class IIa); (2) timing of complete revascularization; (3) antiplatelet therapy in patient with high-bleeding risk. Reflecting rapid advances in the field, the Task Force on Primary PCI of the CVIT group has now proposed an updated expert consensus document for the management of ACS focusing on procedural aspects of primary PCI in 2024 version.

Prognostic Value of Coronary Angiography-Derived Index of Microcirculatory Resistance in Non-ST-Segment Elevation Myocardial Infarction Patients

BACKGROUND

The index of microcirculatory resistance is a reliable measure for evaluating coronary microvasculature, but its prognostic value in patients with non-ST-segment elevation myocardial infarction (NSTEMI) remains unclear.

OBJECTIVES

This study aimed to evaluate the prognostic impact of postpercutaneous coronary intervention (PCI) angiography-derived index of microcirculatory resistance (angio-IMR) in patients with NSTEMI.

METHODS

The culprit vessel's angio-IMR was measured after PCI in 2,212 NSTEMI patients at 3 sites. The primary endpoint was 2-year major adverse cardiac events (MACEs), defined as a composite of cardiac death, readmission for heart failure, myocardial reinfarction, and target vessel revascularization.

RESULTS

The mean post-PCI angio-IMR was 20.63 ± 4.17 in NSTEMI patients. A total of 206 patients were categorized as the high post-PCI angio-IMR group according to maximally selected log-rank statistics. Patients with angio-IMR >25 showed a higher rate of MACEs than those with angio-IMR ≤25 (32.52% vs 9.37%; P < 0.001). Post-PCI angio-IMR >25 was an independent predictor of MACEs (HR: 4.230; 95% CI: 3.151-5.679; P < 0.001) and showed incremental prognostic value compared with conventional risk factors (AUC: 0.774 vs 0.716; P < 0.001; net reclassification index: 0.317; P < 0.001; integrated discrimination improvement: 0.075; P < 0.001).

CONCLUSIONS

In patients undergoing PCI for NSTEMI, an increased post-PCI angio-IMR is associated with a higher risk of MACEs. The addition of post-PCI angio-IMR into conventional risk factors significantly improves the ability to reclassify patients and estimate the risk of MACEs. (Angiograph-Derived Index of Microcirculatory Resistance in Patients With Acute Myocardial Infarction; NCT05696379).

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.

Beyond Coronary Artery Disease: Assessing the Microcirculation

Ischemic heart disease (IHD) affects more than 20 million adults in the United States. Although classically attributed to atherosclerosis of the epicardial coronary arteries, nearly half of patients with stable angina and IHD who undergo invasive coronary angiography do not have obstructive epicardial coronary artery disease. Ischemia with nonobstructive coronary arteries is frequently caused by microvascular angina with underlying coronary microvascular dysfunction (CMD). Greater understanding the pathophysiology, diagnosis, and treatment of CMD holds promise to improve clinical outcomes of patients with ischemic heart disease.

Myocardial Ischemia: Differentiating between Epicardial Coronary Artery Atherosclerosis, Microvascular Dysfunction and Vasospasm in the Catheterization Laboratory

Ischemic heart disease is currently the most common cause of mortality and morbidity worldwide. Although myocardial ischemia is classically determined by epicardial coronary atherosclerosis, up to 40% of patients referred for coronary angiography have no obstructive coronary artery disease (CAD). Ischemia with non-obstructive coronary artery disease (INOCA) has typically been underestimated in the past because, until recently, its prognostic significance was not completely clear. This review aims to highlight differences and patterns in myocardial ischemia caused by epicardial obstructive CAD, coronary microvascular dysfunction (CMD) or vasomotor abnormalities and to elucidate the state of the art in correctly diagnosing these different patterns.

Prognostic Value of Integrated Assessment of Cardiac Magnetic Resonance-Derived Global Coronary Flow Reserve and Cardiopulmonary Exercise Testing-Derived Peak Oxygen Consumption in Patients With Acute Myocardial Infarction

Background: This study investigated the prognostic value of cardiovascular magnetic resonance (CMR)-derived global coronary flow reserve (G-CFR) in addition to cardiopulmonary exercise testing (CPET) variables in patients with acute myocardial infarction (AMI). Methods and Results: We investigated 127 patients with AMI who underwent primary or urgent percutaneous coronary intervention (PCI) and post-intervention CMR and CPET. The incidence of major cardiac and cerebrovascular events (MACCE), defined as all-cause death, recurrent non-fatal myocardial infarction, re-hospitalization due to congestive heart failure, and stroke, was evaluated (median follow-up, 2.8 years). Patients with MACCE (n=14) had lower ejection fraction (EF) (50 [43-59] vs. 58 [51-63]%; P=0.014), lower G-CFR (1.74 [1.19-2.20] vs. 2.40 [1.61-3.66]; P=0.008), and lower peak oxygen consumption (V̇O2) (15.16±2.64 vs. 17.19±3.70 mL/kg/min; P=0.049) than patients without MACCE. G-CFR<2.33 and peak V̇O2 <15.65 mL/kg/min (cut-off values derived from receiver operating characteristic curve analyses) were significantly associated with the incidence of MACCE (log-rank test, P=0.01). The combination of low G-CFR and low peak V̇O2 improved risk discrimination for MACCE when added to the reference clinical model including age, male sex, post-PCI peak creatine kinase, EF, and left anterior descending artery culprit lesion. Conclusions: G-CFR and peak V̇O2 showed incremental prognostic information compared with the reference model using historically important clinical risk factors, indicating that this approach may help identify high-risk patients who suffer subsequent adverse events.

Coronary slow flow and angiography-derived index of microcirculatory resistance as prognostic predictors in patients with angina and normal coronary arteries: a retrospective cohort study

BACKGROUND

This study aims to investigate prognostic implications of coronary slow flow (CSF) and angiography-derived index of microcirculatory resistance (caIMR) in patients with angina and normal coronary arteries.

METHODS

A total of 582 patients were enrolled with angiographically normal coronary arteries. caIMR was calculated using a commercial software. Patients were followed up for a median of 45 months. The primary endpoint was defined as major adverse cardiovascular events (MACEs) comprising death, myocardial infarction and readmission for angina or heart failure.

RESULTS

CSF was diagnosed when TIMI grade 2 flow presented in at least one coronary artery. Multivariate analysis indicated TIMI-flow-based determination of CSF was not significantly associated with MACEs [hazard ratio (HR): 2.14; 95% confidence interval (CI): 0.87-5.31; p = 0.099), while caIMR >42 (HR: 2.53; 95% CI: 1.02-6.32; p = 0.047) were independent predictors of MACEs. Incorporation of caIMR improved the area under the curve from 0.587 to 0.642.

CONCLUSIONS

caIMR was an independent prognostic factor of long-term cardiovascular events in patients with CSF. Evaluation of caIMR improved the risk stratification of patients with angiographically-normal coronary arteries.

Diagnostic value of angiography-derived index of microcirculatory resistance (AMR) for coronary microcirculatory dysfunction (CMD) and its prognostic significance in patients with chronic coronary syndromes in the smoking population

This study aims to analyze the prognostic significance of angiographic microvascular resistance (AMR) derived from functional coronary angiography in diagnosing coronary microvascular dysfunction (CMD) among patients with chronic coronary syndrome (CCS), particularly focusing on the prognostic significance of CMD in smokers. Additionally, this study assesses the prognostic significance of the diagnostic accuracy of the AMR index for CMD in CCS patients within the smoking population. Seventy-five CCS patients were studied for IMR measurement between June 2018 and December 2020, classified into CMD and non-CMD groups. Pearson correlation analyzed AMR and IMR relationship, while ROC curves determined AMR's predictive value for CMD with optimal cutoff value. An additional 223 CCS patients were included for AMR measurements. The study's primary endpoint was MACE occurrence, followed up through telephone calls. COX one-way analysis and Kaplan-Meier analysis evaluated the association between AMR and MACE risk. In the study, 52% of patients were diagnosed with CMD, and the AUC under the AMR curve for predicted IMR ≥ 25 was 0.90 (95% CI: 0.79-0.95). The CMD group had a higher proportion of female patients, smokers, and those with hypertension and diabetes mellitus compared to the non-CMD group (all P < .05). The CMD group exhibited higher AMR values than the non-CMD group (3.20 ± 0.5 vs 1.95 ± 0.45, P < .01), with a significant correlation between AMR and IMR (R2 = 0.81, P < .001). The ROC curve illustrated AMR's effectiveness in diagnosing CMD in CCS patients, using IMR as the gold standard, with the optimal cutoff value of AMR = 2.6mmHgs/cm (sensitivity: 90.5%, specificity: 81.5%). Patients with AMR ≥ 2.6mmHgs/cm had a higher risk of MACE events (HR = 6.00; 95% CI: 1.59-22.67). AMR in patients with CCS was significantly correlated with IMR and demonstrated good diagnostic accuracy. AMR ≥ 2.6 mm Hg*s/cm was associated with an increased risk of MACE occurrence and served as a valuable prognostic factor. In patients with CCS, AMR has a high diagnostic performance, In patients with CCS who smoke, impaired coronary microvascular function as assessed by AMR is significant and is an independent predictor of MACE.

Beyond Coronary Artery Disease: Assessing the Microcirculation

Ischemic heart disease (IHD) affects more than 20 million adults in the United States. Although classically attributed to atherosclerosis of the epicardial coronary arteries, nearly half of patients with stable angina and IHD who undergo invasive coronary angiography do not have obstructive epicardial coronary artery disease. Ischemia with nonobstructive coronary arteries is frequently caused by microvascular angina with underlying coronary microvascular dysfunction (CMD). Greater understanding the pathophysiology, diagnosis, and treatment of CMD holds promise to improve clinical outcomes of patients with ischemic heart disease.

Relationship between the Selvester QRS Score and Coronary Microvascular Dysfunction Assessed by the Index of Microcirculatory Resistance

Objective The index of microvascular resistance (IMR) is an invasive method for quantifying the coronary microvasculature independent of the presence and degree of epicardial stenosis during cardiac catheterization, whereas the Selvester QRS score, which is related to myocardial damage, is a relatively simple and non-invasive measurement procedure. We investigated the relationship between the QRS score and coronary microvascular dysfunction (CMD) assessed via IMR. Methods Data from 74 patients who underwent invasive coronary physiological measurements were retrospectively reviewed. Using a coronary wire, we measured IMR by the hyperemic mean transit time and distal coronary pressure. We also determined a simplified QRS score following the Selvester QRS score criteria by 12-lead electrocardiography. After determining the best cutoff value for the QRS score to predict IMR ≥25, which was defined as CMD by the Coronary Vasomotion Disorders International Study Group, patients were categorized into the QRS score ≥3 (n=16) and the QRS score 0-2 (n=58) groups. Results IMR in the QRS score ≥3 group was significantly higher in comparison to the QRS score 0-2 group (31; IQR: 19-57 vs. 20; IQR: 14-29, p<0.01). The percentage of patients with IMR ≥25 in the QRS score ≥3 group was significantly higher than that in the QRS score 0-2 group (69% vs. 34%, p=0.01). Conclusion A higher QRS score was associated with CMD, as estimated by IMR. The Selvester QRS score is noninvasive parameter that is potentially useful for predicting CMD.

Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 1

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of evidence that has led to major recommendations in clinical practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region based on updated information in the field that including both wire- and image-based physiologic assessment. This is Part 1 of the whole consensus document, which describes the general concept of coronary physiology, as well as practical information on the clinical application of physiologic indices and novel image-based physiologic assessment.

#FullPhysiology: a systematic step-by-step guide to implement intracoronary physiology in daily practice

#FullPhysiology is a comprehensive and systematic approach to evaluate patients with suspected coronary disease using PressureWire technology (Abbott Vascular, Santa Clara, CA, USA). This advancement in technology enables the investigation of each component of the coronary circulation, including epicardial, microvascular, and vasomotor function, without significantly increasing procedural time or technical complexity. By identifying the predominant physiopathology responsible for myocardial ischemia, #FullPhysiology enhances precision medicine by providing accurate diagnosis and facilitating tailored interventional or medical treatments. This overview aims to provide insights into modern coronary physiology and describe a systematic approach to assess epicardial flow-limiting disease, longitudinal physiological vessel analysis, microvascular and vasomotor dysfunction, as well as post- percutaneous coronary intervention (PCI) physiological results.

Early Effects of Ticagrelor Versus Clopidogrel on Peripheral Endothelial Function After Non-ST-Elevation Acute Coronary Syndrome and Assessment of Its Relationship With Coronary Microvascular Function

Peripheral endothelial dysfunction is an independent predictor of adverse long-term prognosis after acute coronary syndrome. Data are lacking on the effects of oral P2Y12-inhibitors on peripheral endothelial function in non-ST-elevation acute coronary syndrome (NSTEACS). Furthermore, the relation between peripheral endothelial function and invasive indexes of coronary microvascular function in NSTEACS is unclear. Between March 2018 and July 2020, hospitalized patients with NSTEACS were randomized (1:1) to ticagrelor or clopidogrel. Peripheral endothelial function was assessed with brachial artery flow-mediated vasodilation (FMD). Invasive indexes of coronary microvascular function were obtained using an intracoronary pressure-temperature sensor-tipped wire. In 70 patients included, mean age was 58.6 years, 78.6% (n = 55) were male and 20% (n = 14) had diabetes mellitus. Compared with clopidogrel, ticagrelor significantly improved FMD (14.2 ± 5.4% vs 8.9 ± 5.3%, p <0.001) after a median treatment time of 41.2 hours. The FMD was significantly correlated with the index of microcirculatory resistance (IMR) measured in the infarct-related artery (r = -0.38, p = 0.001), with a stronger correlation found in those who did not have percutaneous coronary intervention (r = -0.52, p = 0.03). Using receiver operating characteristic curve analysis, an FMD of 8.2% identified an IMR of >34 as the threshold, with 77.6% sensitivity and 52.4% specificity. In patients who did not have a percutaneous coronary intervention, an FMD of 11.49% identified an IMR of >34 with 84.6% sensitivity and 80% specificity. In conclusion, ticagrelor significantly improved peripheral endothelial function compared with clopidogrel in patients with NSTEACS. There was a significant correlation between brachial artery FMD and IMR of the infarct-related artery.

Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA): Focus on Coronary Microvascular Dysfunction and Genetic Susceptibility

Among the most common causes of death worldwide, ischemic heart disease (IHD) is recognized to rank first. Even if atherosclerotic disease of the epicardial arteries is known as the leading cause of IHD, the presence of myocardial infarction with non-obstructive coronary artery disease (MINOCA) is increasingly recognized. Notwithstanding the increasing interest, MINOCA remains a puzzling clinical entity that can be classified by distinguishing different underlying mechanisms, which can be divided into atherosclerotic and non-atherosclerotic. In particular, coronary microvascular dysfunction (CMD), classifiable in non-atherosclerotic mechanisms, is a leading factor for the pathophysiology and prognosis of patients with MINOCA. Genetic susceptibility may have a role in primum movens in CMD. However, few results have been obtained for understanding the genetic mechanisms underlying CMD. Future studies are essential in order to find a deeper understanding of the role of multiple genetic variants in the genesis of microcirculation dysfunction. Progress in research would allow early identification of high-risk patients and the development of pharmacological, patient-tailored strategies. The aim of this review is to revise the pathophysiology and underlying mechanisms of MINOCA, focusing on CMD and actual knowledge about genetic predisposition to it.

Beyond Coronary Artery Disease: Assessing the Microcirculation

Ischemic heart disease (IHD) affects more than 20 million adults in the United States. Although classically attributed to atherosclerosis of the epicardial coronary arteries, nearly half of patients with stable angina and IHD who undergo invasive coronary angiography do not have obstructive epicardial coronary artery disease. Ischemia with nonobstructive coronary arteries is frequently caused by microvascular angina with underlying coronary microvascular dysfunction (CMD). Greater understanding the pathophysiology, diagnosis, and treatment of CMD holds promise to improve clinical outcomes of patients with ischemic heart disease.

Diagnostic Performance of On-Site Computed Tomography Derived Fractional Flow Reserve on Non-Culprit Coronary Lesions in Patients with Acute Coronary Syndrome

The role of coronary computed tomography angiography (CCTA) derived fractional flow reserve (CT-FFR) in the assessment of non-culprit lesions (NCL) in patients with acute coronary syndrome (ACS) is debated. In this prospective clinical study, a total of 68 ACS patients with 89 moderate (30−70% diameter stenosis) NCLs were enrolled to evaluate the diagnostic accuracy of on-site CT-FFR compared to invasive fractional flow reserve (FFRi) and dobutamine stress echocardiography (DSE) as reference standards. CT-FFR and FFRi values ≤0.80, as well as new or worsening wall motion abnormality in ≥2 contiguous segments on the supplying area of an NCL on DSE, were considered positive for ischemia. Sensitivity, specificity, positive, and negative predictive value of CT-FFR relative to FFRi and DSE were 51%, 89%, 75%, and 74% and 37%, 77%, 42%, and 74%, respectively. CT-FFR value (β = 0.334, p < 0.001) and CT-FFR drop from proximal to distal measuring point [(CT-FFR drop), β = −0.289, p = 0.002)] were independent predictors of FFRi value in multivariate linear regression analysis. Based on comparing their receiver operating characteristics area under the curve (AUC) values, CT-FFR value and CT-FFR drop provided better discriminatory power than CCTA-based minimal lumen diameter stenosis to distinguish between an NCL with positive and negative FFRi [0.77 (95% Confidence Intervals, CI: 0.67−0.86) and 0.77 (CI: 0.67−0.86) vs. 0.63 (CI: 0.52−0.73), p = 0.029 and p = 0.043, respectively]. Neither CT-FFR value nor CT-FFR drop was predictive of regional wall motion score index at peak stress (β = −0.440, p = 0.441 and β = 0.403, p = 0.494) or was able to confirm ischemia on the territory of an NCL revealed by DSE (AUC = 0.54, CI: 0.43−0.64 and AUC = 0.55, CI: 0.44−0.65, respectively). In conclusion, on-site CT-FFR is superior to conventional CCTA-based anatomical analysis in the assessment of moderate NCLs; however, its diagnostic capacity is not sufficient to make it a gatekeeper to invasive functional evaluation. Moreover, based on its comparison with DSE, CT-FFR might not yield any information on the microvascular dysfunction in the territory of an NCL.

Prognostic value of coronary microvascular dysfunction assessed by coronary angiography-derived index of microcirculatory resistance in diabetic patients with chronic coronary syndrome

Background

Coronary microvascular dysfunction (CMD) is common and is associated with unfavorable cardiovascular events in patients with diabetes mellitus (DM). Coronary angiography-derived index of microcirculatory resistance (caIMR) is a recently developed wire- and hyperemic agent-free method to assess CMD. We aimed to investigate the prognostic impact of CMD assessed by caIMR on clinical outcomes in patients with DM and chronic coronary syndrome (CCS).

Methods

CCS patients who underwent coronary angiography between June 2015 to May 2018 were included. Coronary microvascular function was measured by caIMR, and CMD was defined as caIMR ≥ 25U. The primary endpoint was major adverse cardiac events (MACE). Kaplan-Meier analysis and Cox proportional hazards models were used to assess the relationship between caIMR and the risk of MACE.

Results

Of 290 CCS patients, 102 patients had DM. Compared with non-diabetic patients, CMD (caIMR ≥ 25U) was higher among DM patients (57.8% vs. 38.3%; p = 0.001). During a mean 35 months follow-up, 40 MACE had occurred. Patients with caIMR ≥ 25 had a higher rate of MACE than patients with caIMR < 25 (20.6% vs. 8.2%, p = 0.002). Of these, the MACE rate was higher among DM patients with caIMR ≥ 25 than those with caIMR < 25 (33.9% vs. 14.0%; p = 0.022). In multivariable Cox analysis, caIMR ≥ 25 was independently associated with MACE in the DM patients but not in non-DM patients (HR, 2.760; 95% CI, 1.066–7.146; P = 0.036).

Conclusion

CMD assessed by caIMR was common and is an independent predictor of MACE among diabetic patients with CCS. This finding potentially enables a triage of higher-risk patients to more intensive therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01653-y.

Coronary flow reserve and cardiovascular outcomes: a systematic review and meta-analysis

AIMS

This meta-analysis aims to quantify the association of reduced coronary flow with all-cause mortality and major adverse cardiovascular events (MACE) across a broad range of patient groups and pathologies.

METHODS AND RESULTS

We systematically identified all studies between 1 January 2000 and 1 August 2020, where coronary flow was measured and clinical outcomes were reported. The endpoints were all-cause mortality and MACE. Estimates of effect were calculated from published hazard ratios (HRs) using a random-effects model. Seventy-nine studies with a total of 59 740 subjects were included. Abnormal coronary flow reserve (CFR) was associated with a higher incidence of all-cause mortality [HR: 3.78, 95% confidence interval (CI): 2.39-5.97] and a higher incidence of MACE (HR 3.42, 95% CI: 2.92-3.99). Each 0.1 unit reduction in CFR was associated with a proportional increase in mortality (per 0.1 CFR unit HR: 1.16, 95% CI: 1.04-1.29) and MACE (per 0.1 CFR unit HR: 1.08, 95% CI: 1.04-1.11). In patients with isolated coronary microvascular dysfunction, an abnormal CFR was associated with a higher incidence of mortality (HR: 5.44, 95% CI: 3.78-7.83) and MACE (HR: 3.56, 95% CI: 2.14-5.90). Abnormal CFR was also associated with a higher incidence of MACE in patients with acute coronary syndromes (HR: 3.76, 95% CI: 2.35-6.00), heart failure (HR: 6.38, 95% CI: 1.95-20.90), heart transplant (HR: 3.32, 95% CI: 2.34-4.71), and diabetes mellitus (HR: 7.47, 95% CI: 3.37-16.55).

CONCLUSION

Reduced coronary flow is strongly associated with increased risk of all-cause mortality and MACE across a wide range of pathological processes. This finding supports recent recommendations that coronary flow should be measured more routinely in clinical practice, to target aggressive vascular risk modification for individuals at higher risk.

Index of microcirculatory resistance: state-of-the-art and potential applications in computational simulation of coronary artery disease

The dysfunction of coronary microcirculation is an important cause of coronary artery disease (CAD). The index of microcirculatory resistance (IMR) is a quantitative evaluation of coronary microcirculatory function, which provides a significant reference for the prediction, diagnosis, treatment, and prognosis of CAD. IMR also plays a key role in investigating the interaction between epicardial and microcirculatory dysfunctions, and is closely associated with coronary hemodynamic parameters such as flow rate, distal coronary pressure, and aortic pressure, which have been widely applied in computational studies of CAD. However, there is currently a lack of consensus across studies on the normal and pathological ranges of IMR. The relationships between IMR and coronary hemodynamic parameters have not been accurately quantified, which limits the application of IMR in computational CAD studies. In this paper, we discuss the research gaps between IMR and its potential applications in the computational simulation of CAD. Computational simulation based on the combination of IMR and other hemodynamic parameters is a promising technology to improve the diagnosis and guide clinical trials of CAD.

Association Between Thrombogenicity Indices and Coronary Microvascular Dysfunction in Patients With Acute Myocardial Infarction

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Our study supports the feasibility of measuring thrombogenicity in patients with acute myocardial infarction, with intent to predict periprocedural and long-term clinical events, in real-world clinical practice.

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Preprocedural assessment of ex vivo thrombogenicity (eg, platelet-fibrin clot strength by thromboelastography) was significantly associated with the risk of coronary microvascular dysfunction.

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A combined risk stratification with coronary microvascular dysfunction and platelet-fibrin clot strength increased the prognostic implication to predict the rates of long-term clinical outcomes.

The association between thrombogenicity and coronary microvascular dysfunction (CMD) has been poorly explored in patients with acute myocardial infarction (AMI). In our real-world clinical practice (N = 116), thrombogenicity was evaluated with thromboelastography and conventional hemostatic measures, and CMD was defined as index of microcirculatory resistance of >40 U using the invasive physiologic test. High platelet-fibrin clot strength (P-FCS) (≥68 mm) significantly increased the risk of postprocedural CMD (odds ratio: 4.35; 95% CI: 1.74-10.89). Patients with both CMD and high P-FCS had a higher rate of ischemic events compared to non-CMD subjects with low P-FCS (odds ratio: 5.58; 95% CI: 1.31-23.68). This study showed a close association between heightened thrombogenicity and CMD and their prognostic implications after reperfusion in acute myocardial infarction patients.

Prognostic impact of coronary microvascular dysfunction in patients with myocardial infarction with non-obstructive coronary arteries

BACKGROUND

Myocardial infarction with non-obstructive coronary arteries (MINOCA) has been and remained a puzzling heterogeneous entity. The index of microcirculatory resistance (IMR) is a quantitative and specific index for the assessment of microvascular function. However, the role of IMR in MINOCA has not yet been studied. This study aimed to evaluate the prognostic value of coronary microvascular function, as assessed by coronary angiography‑derived index of microvascular resistance (caIMR) in MINOCA patients.

METHOD

This study included 109 MINOCA patients. Microvascular function was assessed by caIMR and was analyzed in 280 coronary arteries. The primary endpoint of the study was MACE, defined as cardiovascular death, nonfatal MI, heart failure, stroke and angina rehospitalization. The best cut-off of caIMR was derived from ROC analysis based on MACE prediction.

RESULTS

The patients were classified into high caIMR (caIMR>43U) and low caIMR (caIMR≤43U) based on a caIMR cut-off value of 43U. High caIMR was observed in 55 (50.5%) patients. A total of 27 MACE occurred during the 2 years of follow-up. MACE rate was significantly higher in patients with high caIMR than in patients with low caIMR (36.4% vs 13.0%, P=0.005). The Kaplan-Meier curves showed a significantly increased risk of MACE in patients with high caIMR (log-rank P=0.001). Cox multivariate analysis showed that caIMR>43 was a highly independent predictor of MACE (HR, 3.08; 95% CI, 1.13 - 8.35; P=0.027).

CONCLUSIONS

caIMR is a strong predictor of clinical outcome among MINOCA patients. The evaluation of IMR can provide an objective risk stratification method for patients with MINOCA.

Impact of a micro-net mesh technology covering stent on coronary microvascular dysfunction in patients with high thrombus burden

BACKGROUND

Highly thrombotic coronary lesions continue to be a serious and clinically significant problem that is not effectively and completely addressed by current technology.

OBJECTIVES

We aimed to investigate whether a micro-net mesh (MNM) technology covering stent could preserve the index of microcirculatory resistance (IMR) after percutaneous coronary intervention (PCI) in patients with high thrombus burden.

METHODS AND RESULTS

Fifty-two patients with non-ST elevation myocardial infarction or ST Elevation Myocardial Infarction and high thrombus burden (TIMI thrombus grade ≥ 3) were randomized into two groups, PCI with a MNM covering stent (MNM group, n = 25) and PCI with any commercially available stent (DES group, n = 27). As the primary endpoint, IMR was measured immediately after PCI using a pressure-temperature sensor-tipped coronary wire. The secondary endpoint was left ventricular ejection fraction (LVEF) at 6 months of follow-up. The IMR in the MNM group was significantly lower in comparison to the DES group (33.2 [21.3, 48.9] vs. 57.2 [39.9, 98.0], p = 0.005). No significant differences were observed in baseline LVEF (54.5 ± 10.2% vs. 53.1 ± 6.87%, p = .57), while LVEF was significantly improved at follow-up in the MNM group (61.1 ± 7.1% vs. 53.9 ± 6.35%, p = .0001).

CONCLUSION

MNM technology significantly improved coronary microvascular dysfunction after PCI in patient with acute coronary syndrome and appears as a useful technological option for thrombus management.

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

Fundamento:

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 IAMCST

Métodos:

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.

Clinical implication of QFR in patients with ST-segment elevation myocardial infarction after drug-eluting stent implantation

The feasibility and prognostic value of quantitative flow ratio (QFR) after percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) patients have not been assessed. The aim of this study was to investigate the prognostic utility of post-PCI QFR to predict outcomes in STEMI and determine the influence of functional results, in both culprit and nonculprit lesions, after PCI. Patients undergoing PCI of culprit lesions and receiving staged procedures of nonculprit lesions after 7 days were enrolled from 2 centers and underwent post-PCI QFR. The primary outcome was the vessel-oriented composite endpoints (VOCEs), defined as vessel-related cardiovascular death, vessel-related myocardial infarction, and target vessel revascularization. Four hundred fifteen vessels (186 culprit lesions and 219 nonculprit lesions) in 186 patients were analyzed. Measured at staged PCI, the post-PCI QFR of culprit lesions was significantly lower than that of nonculprit lesions (0.92 ± 0.10 versus 0.95 ± 0.08, p < 0.001). The multivariable model demonstrated that low post-PCI QFR was an independent predictor of 2-year VOCE (20.8% versus 5.7%; hazard ratio 2.718; 95% CI 1.347-5.486; p = 0.005). In STEMI patients with a low angiography-derived index of microcirculatory resistance (≤ 40U), a good correlation and agreement between post-PCI QFR value of culprit lesions at primary and staged procedures (r = 0.942; mean difference: - 0.0017 [- 0.074 to 0.070]) was identified. In conclusion, culprit lesions suffered from suboptimal functional results more frequently compared to nonculprit lesions after PCI in STEMI patients. Low post-PCI QFR was associated with subsequent adverse clinical outcomes. After stenting, culprit lesions may feasibly be assessed through QFR without significant microvascular dysfunction.

Effects of different strategies on high thrombus burden in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary catheterization

OBJECTIVE

This study aimed at evaluating efficacy and safety of thrombus aspiration and intracoronary-targeted thrombolysis on coronary thrombus burden in ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous catheterization, comparing their effects on myocardial perfusion through index of microcirculatory resistance (IMR) and single-photon emission computed tomography (SPECT).

PARTICIPANTS AND METHODS

From January 2017 to January 2018, STEMI patients with high thrombus burden undergoing primary catheterization were enrolled and randomly assigned to receiving thrombus aspiration (TA group) or intracoronary thrombolysis (IT group). IMR, SPECT, and other conventional measurements were adopted to assess myocardial perfusion. Major adverse cardiovascular events (MACEs) and complications were recorded over a 90-day follow-up and a 12-month follow-up after the procedure.

RESULTS

The study consisted of 38 patients in the IT group and 33 in the TA group. After recanalization, thrombus burden score, corrected thrombolysis in myocardial infarction (TIMI) frame count, the proportion of TIMI myocardial perfusion 3 grade, and IMR in the IT group were significantly better than those of the TA group (P<0.05). During the 90-day follow-up, no difference was observed in cardiac function and MACEs. During the 12-month follow-up, there were significant differences in infarct size of SPECT (18.56±8.56 vs. 22.67±7.66, P=0.046), left ventricular ejection fraction of echocardiography (58.13±5.92 vs. 55.17±5.68, P=0.043), and the composite MACEs between the two groups (P=0.034).

CONCLUSION

Thrombus aspiration and intracoronary-targeted thrombolysis are effective and safe strategies in managing high coronary thrombus burden in STEMI patients. Compared with aspiration, intracoronary-targeted thrombolysis is more beneficial in improving myocardial microcirculation perfusion.

Why, When and How Should Clinicians Use Physiology in Patients with Acute Coronary Syndromes?

Current data support the use of coronary physiology in patients with acute coronary syndrome (ACS). In patients with ST-elevation MI, the extent of myocardial damage and microvascular dysfunction create a complex conundrum to assimilate when considering clinical management and risk stratification. In this setting, the index of microcirculatory resistance emerged as an accurate tool to identify patients at risk of suboptimal myocardial reperfusion after primary percutaneous coronary intervention who may benefit from novel adjunctive therapies. In the context of non-ST-elevation ACS, coronary physiology should be carefully interpreted and often integrated with intracoronary imaging, especially in cases of ambiguous culprit lesion. Conversely, the functional assessment of bystander coronary disease is favoured by the available evidence, aiming to achieve complete revascularisation. Based on everyday clinical scenarios, the authors illustrate the available evidence and provide recommendations for the functional assessment of infarct-related artery and non-culprit lesions in patients with ACS.

A randomized controlled trial of a physiology-guided percutaneous coronary intervention optimization strategy: Rationale and design of the TARGET FFR study

Post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) ≥0.90 confers an improved cardiac prognosis. There are currently limited data available to determine how often it is possible to improve an angiographically acceptable but physiologically suboptimal result. A physiology-guided optimization strategy can achieve a clinically meaningful increase in the proportion of patients achieving a final post-PCI FFR ≥0.90 compared to standard care. Following angiographically successful PCI procedures, 260 patients will be randomized (1:1) to receive either a physiology-guided incremental optimization strategy (intervention group) or blinded post-PCI coronary physiology measurements (control group). Patients undergoing successful, standard-of-care PCI for either stable angina or non-ST-segment-elevation myocardial infarction who meet the study's inclusion and exclusion criteria will be eligible for randomization. The primary endpoint is defined as the proportion of patients with a final post-PCI FFR result ≥0.90. Secondary endpoints include change from baseline in Seattle Angina Questionnaire and EQ-5D-5L scores at 3 months and the rate of target vessel failure and its components (cardiac death, myocardial infarction, stent thrombosis, unplanned rehospitalization with target vessel revascularization) at 3 months and 1 year. 260 individual patients were successfully randomized between March 2018 and November 2019. Key baseline demographics of the study population are reported within. TARGET FFR is an investigator-initiated, prospective, single-center, randomized controlled trial of an FFR-guided PCI optimization strategy. The study has completed recruitment and is now in clinical follow-up. It is anticipated that primary results will be presented in Autumn 2020. ClinicalTrials.gov Identifier: NCT03259815. [Correction added on Apr 3 2020, after first online publication: Clinical Trials identifier added.].

Comparison of the Effects of Ticagrelor and Clopidogrel on Microvascular Dysfunction in Patients With Acute Coronary Syndrome Using Invasive Physiologic Indices

Background:

Ticagrelor reduced the rate of myocardial infarction and death compared with clopidogrel in patients with acute coronary syndrome. However, little is understood about chronic treatment of ticagrelor on microvascular dysfunction. The objective of this study was to assess the impact of ticagrelor maintenance treatment on microvascular system and coronary flow in comparison with clopidogrel.

Methods:

This study was a nonblinded, open-label, parallel-group, prospective, randomized controlled trial that enrolled 120 patients with acute coronary syndrome requiring stent implantation. Patients were randomized into the ticagrelor (180 mg loading dose, 90 mg twice daily thereafter) or clopidogrel (300 to 600 mg loading dose, 75 mg daily thereafter) group. The primary end point was coronary microvascular dysfunction as measured by an index of microcirculatory resistance (IMR) at 6 months after treatment.

Results:

The baseline clinical characteristics and physiological parameters, such as fractional flow reserve, coronary flow reserve, and IMR, did not differ between the ticagrelor and clopidogrel groups. Six-month follow-up physiological data showed that the IMR value was significantly lower in the ticagrelor group than the clopidogrel group (15.57±5.65 versus 21.15±8.39, P <0.01), and coronary flow reserve was higher in the ticagrelor group than in the clopidogrel group (3.85±0.72 versus 3.37±0.76, P <0.01). However, there was no difference in fractional flow reserve (0.87±0.08 versus 0.87±0.09, P =0.94) between the 2 groups. The improvement in IMR after 6 months of treatment was higher in the ticagrelor group ( P <0.01). Analyses of 223 nonculprit vessels of registered patients based on physiological results showed no differences in baseline fractional flow reserve (0.93±0.13 versus 0.92±0.09, P =0.58), coronary flow reserve (3.62±1.27 versus 3.51±1.24, P =0.16), or IMR (21.37±12.37 versus 24.19±21.08, P =0.22) or in follow-up fractional flow reserve (0.91±0.09 versus 0.91±0.08, P =0.67), coronary flow reserve (3.91±1.22 versus 3.75±1.16, P =0.36), or IMR (19.43±10.32 versus 21.52±18.90, P =0.34) between the 2 groups.

Conclusions:

Compared with clopidogrel, 6 months of ticagrelor therapy significantly improved microvascular dysfunction in acute coronary syndrome patients with stent implantation.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02618733.

When small vessels become big problems! Microvascular dysfunction in NSTEMI

In a carefully selected cohort of 83 NSTEMI patients, there was a wide variation in the index of microcirculatory resistance (IMR) Elevated IMR, which correlates with microvascular obstruction by MRI, was an independent predictor of adverse cardiovascular outcomes in patients with NSTEMI Further investigation is warranted to understand the influence of the microvascular on prognosis following myocardial infarction.

Relationship between the ST-Segment Resolution and Microvascular Dysfunction in Patients Who Underwent Primary Percutaneous Coronary Intervention

Objectives

Incomplete ST-segment elevation resolution (STR) occasionally occurs despite successful revascularization of epicardial coronary artery after primary percutaneous coronary intervention (PPCI). The aim of this study was to evaluate the relationship between the degree of STR and the severity of microvascular dysfunction.

Methods

A total of 73 consecutive patients with ST-segment elevation myocardial infarction (STEMI) who underwent successful PPCI were evaluated. Serial 12-lead electrocardiography was performed at baseline and at 90 minutes after PPCI. Microvascular dysfunction was assessed by index of microvascular resistance (IMR) immediately after PPCI.

Results

Patients were classified into 2 groups: 50 patients with complete STR (STR ≥50%) and 23 patients with incomplete STR (STR <50%). The incomplete STR group had a higher IMR value and lower left ventricular ejection fraction (LVEF), compared with the complete STR group. The degree of STR was significantly correlated with IMR (r = −0.416, P=0.002) and LVEF (r = 0.300, P=0.011). These correlations were only observed in patients with left anterior descending artery (LAD) infarction but not observed in patients with non-LAD infarction. A cutoff IMR value was 27.3 for predicting incomplete STR after PPCI.

Conclusion

Incomplete STR after PPCI in patients with STEMI reflects the presence of microvascular and left ventricular dysfunction, especially in patients with LAD infarction.