Assessing and managing coronary microcirculation dysfunction in acute ST-segment elevation myocardial infarction

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.

Angiography-Derived and Sensor-Wire Methods to Assess Coronary Microvascular Dysfunction in Patients With Acute Myocardial Infarction

ST-segment elevation myocardial infarction (STEMI) treatment with primary percutaneous coronary intervention has dramatically impacted prognosis. However, despite satisfactory angiographic result, occurrence or persistence of coronary microvascular dysfunction after revascularization still affects long-term outcomes. The diagnostic and therapeutic value of understanding the status of coronary microcirculation is gaining attention in the cardiology community. However, current methods to assess microvascular function (namely, cardiac magnetic resonance and invasive wire-based coronary physiology) remain, at least in part, limited by technical and logistic aspects. On the other hand, angiography-based indices of microcirculatory resistance are emerging as valid and user-friendly tools with potential impact on prognostic stratification of patients with STEMI. This review provides an overview about conventional and novel methods to assess coronary microvascular dysfunction in patients with STEMI. The authors also provide a proposed procedural algorithm to facilitate optimal use of wire-based and angiography-based indices in the acute setting of STEMI.

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.

A novel CFD-based computed index of microcirculatory resistance (IMR) derived from coronary angiography to assess coronary microcirculation

OBJECTIVES

This study sought to present a novel approach for computation of the index of microcirculatory resistance (IMR) and to evaluate its diagnostic performance.

BACKGROUND

IMR is a quantitative assessment to identify coronary microvascular dysfunction. However, its clinical use remains extremely limited. Calculation of IMR from coronary angiography images may increase the utility of coronary microvasculature assessment.

METHODS

203 patients with 203 vessels were included in this study. Physiology measurements were obtained with pressure-wire in the whole cohort. The computational fluid dynamics (CFD)-based AccuIMR was computed and evaluated in a blinded fashion using wire-based IMR as the reference standard.

RESULTS

The overall diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of AccuIMR for detecting coronary microvascular disease were 91.1% (95% CI: 86.4% to 94.7%), 89.4% (95% CI: 80.9% to 95.0%), 92.4% (95% CI: 86.0% to 96.5%), 89.4% (95% CI: 81.8% to 94.1%), and 92.2% (95% CI: 86.7% to 95.8%), respectively. The correlation coefficient equaled to 0.81 (p < 0.001) between AccuIMR and wire-based IMR with the receiver-operating curve had area under the curve of 0.924 (95% CI: 0.878 to 0.956).

CONCLUSIONS

AccuIMR is a novel pressure-wire free approach to assess coronary microvascular disease with great diagnostic performance, which can be a valid, efficient, and cost-reducing tool to provide an easier routine assessment of coronary microcirculation.

Usefulness of echocardiographic myocardial work in evaluating the microvascular perfusion in STEMI patients after revascularization

Background

Left ventricular myocardial work (MW) assessed by echocardiography has recently been introduced as a new index of global and regional myocardial performance. The presence of microvascular obstruction after revascularization in ST-segment elevation myocardial infarction (STEMI) patients predicts poor clinical outcomes. This study aimed to explore the usefulness of MW in identifying impaired microvascular perfusion (MVP) in the patients with STEMI after revascularization.

Methods

One hundred and sixty STEMI patients who underwent myocardial contrast echocardiography (MCE) within 48 h after percutaneous coronary intervention (PCI) were included. Patients were divided into normal MVP and impaired MVP groups according to the myocardial perfusion score. The clinical data, coronary angiography results and echocardiographic data including Global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE) were collected.

Results

Impaired MVP was found in 60% of patients. Compared with the normal MVP group, GWI (909.2 ± 287.6 mmHg% vs. 1191.2 ± 378.2 mmHg%), GCW (1198.3 ± 339.6 mmHg% vs. 1525.9 ± 420.5 mmHg%), GWE (82.7 ± 7.8% vs. 86.8 ± 5.6%) and GLS (− 11.0 ± 3.4% vs. − 14.4 ± 3.8%) were significantly reduced in the impaired MVP group. Whereas there was no statistically significant difference in left ventricular ejection fraction (LVEF) and GWW, multivariate logistic regression analysis showed that peak troponin I (OR 1.017, 95% CI 1.006–1.029; P = 0.004), final TIMI flow ≤ 2 (OR 16.366, 95% CI 1.998–134.06; P = 0.009), left ventricular end-diastolic volume index (LVEDVi) (OR 1.139 95% CI 1.048–1.239; P = 0.002), and GWI (OR 0.997 95% CI 0.994–1.000; P = 0.029) were independently associated with impaired MVP. GWI showed a good sensitivity (86.8%) but low specificity (53.7%) in identifying impaired MVP (AUC 0.712, 95% CI 0.620–0.804; P < 0.001). Combination with GWI can improve the diagnostic value of TNI or LVEVi for impaired MVP.

Conclusion

Impaired MVP is relatively common in STEMI patients after revascularization and independently associated with left ventricular GWI assessed by echocardiography. GWI confer incremental value to MVP assessment in STEMI patients.

Pressure-controlled intermittent coronary sinus occlusion improves the vasodilatory microvascular capacity and reduces myocardial injury in patients with STEMI

BACKGROUND

Preliminary data suggest that pressure-controlled intermittent coronary sinus occlusion (PICSO) might reduce the infarct size (IS) in patients with anterior ST-elevation myocardial infarction (STEMI). However, the applicability of this therapy to patients with inferior STEMI and its exact mechanism of action is uncertain.

METHODS AND RESULTS

Thirty-six patients (27 anterior and 9 inferior) with STEMI underwent PICSO-assisted-primary percutaneous intervention (PPCI) and were compared with matched controls who underwent standard PCI (n = 72). Median age was 63 (55-70) years and 82% were male. Coronary microvascular status was assessed using thermodilution-derived index of microcirculatory resistance (IMR) and the vasodilatory capacity was assessed using the resistive reserve ratio (RRR). IS and microvascular obstruction (MVO) were assessed using cardiovascular magnetic resonance imaging (CMR) within 48 h and 6 months of follow-up. At completion of PPCI, IMR improved significantly in PICSO-treated patients compared with controls in patients with either anterior (63.7 [49.8-74.6] vs. 35.9 [27.9-47.6], p < 0.001) or inferior STEMI (60.0 [47.6-67.1] vs. 22.7 [18.4-35.0], p < 0.001). RRR significantly improved after PICSO treatment for anterior (1.21 [1.01-1.42] vs. 1.73 [1.51-2.16], p = 0.002) or inferior STEMI (1.39 [1.05-1.90] vs. 2.87 [2.17-3.78], p = 0.001), whereas it did not change in controls compared with baseline. Patients treated with PICSO presented significantly less frequently with MVO (66.6% vs. 86.1%, p = 0.024) and smaller 6-month IS compared with controls (26% [17%-30%] vs. 30% [21%-37%], p = 0.045).

CONCLUSION

PICSO therapy may improve microvascular function and vasodilatory capacity, which contributes to reducing IS in patients with STEMI undergoing PPCI.

Microcirculation during surgery

Throughout the long history of surgery, there has been great advancement in the hemodynamic management of surgical patients. Traditionally, hemodynamic management has focused on macrocirculatory monitoring and intervention to maintain appropriate oxygen delivery. However, even after optimization of macro-hemodynamic parameters, microcirculatory dysfunction, which is related to higher postoperative complications, occurs in some patients. Although the clinical significance of microcirculatory dysfunction has been well reported, little is known about interventions to recover microcirculation and prevent microcirculatory dysfunction. This may be at least partly caused by the fact that the feasibility of monitoring tools to evaluate microcirculation is still insufficient for use in routine clinical practice. However, considering recent advancements in these research fields, with more popular use of microcirculation monitoring and more clinical trials, clinicians may better understand and manage microcirculation in surgical patients in the future. In this review, we describe currently available methods for microcirculatory evaluation. The current knowledge on the clinical relevance of microcirculatory alterations has been summarized based on previous studies in various clinical settings. In the latter part, pharmacological and clinical interventions to improve or restore microcirculation are also presented.

The role of myocardial work in evaluating coronary microcirculation of STEMI patients after percutaneous coronary intervention

BACKGROUND

Despite of restoring epicardial infarct-related artery(IRA) patency after myocardial infarction, microvascular reperfusion were not achieved sometimes, and the deterioration of myocardial perfusion persists in a considerable number of patients. This phenomenon is known as microvascular obstruction (MVO). MVO is often observed in ST-Segment Elevation Myocardial Infarction(STEMI) patients, even if percutaneous coronary intervention (PCI) was successful. In addition, some evidence has indicated that the presence of MVO predicted poor clinical outcomes independent of myocardial infarct size. Noninvasive as well as invasive modes for assessing microvascular perfusion(MVP) are complex, time consuming, and expensive have, there is yet no simple method available at present to assess coronary microcirculation. In this research, we attempt to evaluate the usefulness of left ventricular myocardial work (LVMW), a new index of myocardial performance, for the assessment of MVP in STEMI patients after PCI.

METHODS

Forty-seven patients with STEMI treated by PCI were enrolled and underwent a transthoracic doppler echocardiography (TTE) within 24-72 hours after PCI. IRA were left anterior descending (LAD) artery (29,62%), left circumflex (LCX) artery(9,19%), right coronary artery (RCA) (9,19%) respectively. Myocardial contrast echocardiography (MCE) was used to evaluate MVP after PCI, then perfusion score index (PSI) was calculated referring to whether the ultrasonic enhancing agents was replenishment or not. Patients were divided into normal MVP and impaired MVP group according to PSI. Left ventricular global longitudinal strain (GLS) was generated by speckle tracking echocardiography(STE) and pressure-strain loops (PSLs) was used to generate global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE). GLS and the MW parameters (GWI, GCW, GWW, GWE) were compared between groups. Receiver operating characteristic (ROC) curves were calculated by plotting sensitivity versus (1-specificity), allowing calculation of the area under the curve (AUC) and the identification of LVMW parameters and GLS cutoff thresholds that best identify STEMI patients with impaired MVP after PCI.

RESULTS

In this study, a statistically significant difference was observed in GWI (1163±405 mm Hg% vs 1617±363 mm Hg%), GCW (1296±430 mm Hg% vs 1789±406 mm Hg%), GWE (83±8.52% vs 90±5.58%) and GLS (11.56±3.29 vs 16.65±3.59) between impaired MVP group and normal MVP group. However, there is no statistical significance difference in left ventricular ejection fraction (LVEF), and GWW. ROC analysis revealed that GCW (cut-off value: 1326 mm Hg%, AUC: .80, sensitivity: 95% and specificity: 56%), GWI (cut-off value: 1281 mm Hg%, AUC: .81, sensitivity: 90% and specificity: 70%), GWE (cut-off value: 90%, AUC: .77, sensitivity: 65% and specificity: 78%) and GLS (cut-off value: 12.5, AUC: .86, sensitivity: 90% and specificity: 67%) have appreciable AUC, sensitivity, and specificity to identify STEMI patients with impaired MVP after PCI.

CONCLUSION

Measuring LVMW indices of STEMI patients after PCI may add adjuvant value for the assessment of MVP.

Relationship Between Plasma Total Homocysteine Levels and Mean Corrected TIMI Frame Count in Patients with Acute Myocardial Infarction

Objective

To explore the relationship between the plasma total homocysteine (tHcy) levels and slow coronary flow (SCF) measured by mean corrected TIMI frame count (CTFC) in patients with acute myocardial infarction (AMI).

Methods

Ninety-one patients with primary myocardial infarction were enrolled in this study. The quantitative measurement of coronary blood flow was performed using the mean CTFC method. Plasma tHcy levels were determined using enzymatic assay from venous blood samples. Multivariable linear regression models indicated were used to estimate the effect size (β) of plasma tHcy levels on mean CTFC levels.

Results

Compared with patients with the mean CTFC ≤23.61 frames per second (FPS) group, there were increased plasma tHcy levels in patients of the second, third and highest mean CTFC quartiles (P < 0.001). Linear regression models indicated that plasma tHcy levels were positively associated with mean CTFC levels (adjusted-β per SD increase: 1.96, 95% CI 1.20 to 2.73, P < 0.001). Compared to the tHcy ≤12.30 μmol/L group, the third and highest tHcy-quartile groups had higher mean CTFC levels (adjusted-β: 2.52, 95% CI 0.39 to 4.65, P = 0.023; adjusted-β: 5.07, 95% CI 2.98 to 7.16, P < 0.001, respectively; P for trend <0.001). Moreover, this positive relationship was modified by diabetes mellitus (P-value for interaction was 0.046).

Conclusion

We found a positive relationship between plasma tHcy levels and mean CTFC levels in patients with AMI. Moreover, diabetes mellitus played an interactive role in this positive association between the plasma tHcy levels and mean CTFC levels.

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.

The role of arginase in the microcirculation in cardiovascular disease

In the microcirculation, the exchange of nutrients, water, gas, hormones, and waste takes place, and it is divided into the three main sections arterioles, capillaries, and venules. Disturbances in the microcirculation can be measured using surrogate parameters or be visualized either indirectly or directly.Arginase is a manganese metalloenzyme hydrolyzing L-arginine to urea and L-ornithine. It is located in different cell types, including vascular cells, but also in circulating cells such as red blood cells. A variety of pro-inflammatory factors, as well as interleukins, stimulate increased arginase expression. An increase in arginase activity consequently leads to a consumption of L-arginine needed for nitric oxide (NO) production by endothelial NO synthase. A vast body of evidence convincingly showed that increased arginase activity is associated with endothelial dysfunction in larger vessels of the vascular tree. Of note, arginase also influences the microcirculation. Arginase inhibition leads to an increase in the bioavailability of NO and reduces superoxide levels, resulting in improved endothelial function. Arginase inhibition might, therefore, be a potent treatment strategy in cardiovascular medicine. Recently, red blood cells emerged as an influential player in the development from increased arginase activity to endothelial dysfunction. As red blood cells directly interact with the microcirculation in gas exchange, this could constitute a potential link between arginase activity, endothelial dysfunction and microcirculatory disturbances.The aim of this review is to summarize recent findings revealing the role of arginase in regulating vascular function with particular emphasis on the microcirculation.

Reflectance spectral analysis for novel characterization and clinical assessment of aspirated coronary thrombi in patients with ST elevation myocardial infarction

OBJECTIVE

The visual appearance of coronary thrombi may be clinically informative in ST elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (pPCI). However, subjective assessment is poorly reproducible and cannot provide an objective basis for treatment decisions or patient stratification. We have assessed the feasibility of a novel reflectance spectroscopy technique to systematically characterize coronary artery thrombi retrieved by aspiration during pPCI in patients with STEMI, and the clinical utility for predicting distal microvascular obstruction.

APPROACH

Patients with STEMI treated with pPCI and thrombus aspiration (n = 288) were recruited from the Oxford Acute Myocardial Infarction (OxAMI) Study. Of these, 158 patients underwent cardiac magnetic resonance imaging within 48 h for assessment of microvascular obstruction (MVO). Coronary thrombi were imaged by reflectance spectroscopy across wavelengths 500-800 nm.

MAIN RESULTS

Spectral data were analysed using function fitting and multivariate models. The coefficient 'c _red' determined from the fitting procedure correlated with the visually-assessed colour of thrombi ('red' or 'white') and with MVO. When applied to a reduced data set, consisting of spectra from 20 patients with the largest MVO and from 20 propensity-score-matched patients with no MVO, three multivariate analysis methods were able to discriminate spectra of thrombi from patients without MVO and with the largest MVO.

SIGNIFICANCE

Reflectance spectral analysis of coronary thrombus provides new insights into the pathology of STEMI, with potential clinical implications for emergency patient care. Further studies are warranted for validation as a point-of-care stratification tool in predicting the degree of microvascular injury and clinical outcomes in STEMI.