Invasive Assessment of the Coronary Microcirculation in Reperfused ST-Segment-Elevation Myocardial Infarction Patients: Where Do We Stand?

Life-Saving Drug or Potential Threat? The Role of Mineralocorticoid Receptor Antagonists in Myocardial Infarction: A Meta-Analysis

Mineralocorticoid receptor antagonists (MRAs) have been studied as a potential therapeutic option to improve outcomes in patients with myocardial infarction (MI). Although several randomized controlled trials have evaluated the effectiveness of MRAs in post-MI patients, the specific effects remain debated. We systematically searched databases including Web of Science, PubMed, Embase, and Cochrane Library. The primary efficacy outcome was death from any cause. Secondary efficacy outcomes included death from cardiovascular causes, death from MI, and others. Subgroup analyses were performed based on the presence of heart failure and the type of MRA used. Safety outcomes included hyperkalemia, hypokalemia, breast tenderness, and gynecomastia. A total of 13 randomized controlled trials involving 17 851 patients were included. The results demonstrated that MRAs significantly reduced the risk of death from any cause (relative risk [RR] 0.87; 95% CI 0.79-0.95; P = .004). Subgroup analysis indicated that the effectiveness of MRAs varied based on the presence of heart failure. MRAs significantly reduced the risk of death from cardiovascular causes in heart failure patients (RR 0.87; 95% CI 0.78-0.97), but had no significant effect in patients without heart failure (RR 0.69; 95% CI 0.34-1.38). Furthermore, subgroup analysis based on different MRA drugs showed varying effects on outcomes. While some adverse events, such as hyperkalemia (RR 1.95; 95% CI 1.55-2.46; P < .01), were significantly more frequent, other safety events did not show significant differences. MRAs improve cardiovascular outcomes in MI patients, especially in those with heart failure. When choosing a specific MRA drug, eplerenone or spironolactone is recommended.

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.

Correlation between abnormal microvascular perfusion and quantitative flow ratio after primary PCI in patients with STEMI

AIMS

Timely assessment of abnormal microvascular perfusion (MVP) may improve prognosis in patients with ST-segment elevation myocardial infarction (STEMI). This study aimed to determine the clinical implications of contrast-flow quantitative flow ratio (cQFR) in evaluating abnormal MVP and subsequent outcomes among STEMI patients after successful primary percutaneous coronary intervention (PPCI).

METHODS

The study population consisted of 2 independent cohorts. The diagnostic cohort was used to evaluate the correlation and diagnostic accuracy of cQFR in predicting abnormal MVP. In this cohort, MVP and cQFR of the culprit vessel (n = 186) were assessed from a prospective consecutive registry. Abnormal MVP was determined using myocardial contrast perfusion echocardiography (MCE) in the culprit vessel after PPCI. The prognostic cohort consisted of STEMI patients undergoing PPCI who were followed for a minimum of 2 years (n = 1931). The primary outcome was all-cause mortality.

RESULTS

In the diagnostic cohort, cQFR exhibited a moderate correlation with abnormal MVP assessed by MCE. Specificity, sensitivity, and area under the curve of post-PPCI cQFR to predict abnormal MVP were 81.6 %, 50.9 % and 0.709 (95 % confidence interval: 0.635-0.783), respectively, with the best cut-off value of 0.875. In the prognostic cohort, patients with cQFR <0.875 showed a significantly higher risk of long-term mortality compared to those with cQFR ≥0.875 (median follow-up: 52 months; mortality: 8.0 % vs. 3.8 %; p < 0.001). Cox-regression analysis revealed that cQFR < 0.875 was an independent predictor of long-term mortality (adjusted HR: 2.132; 95 % CI: 1.358-3.346; p = 0.001) after adjusting for age, gender, diabetes mellitus, hyperlipidemia, symptom to balloon time, culprit vessel.

CONCLUSIONS

We found that cQFR demonstrated a relatively good performance in predicting abnormal MVP in patients with STEMI after successful PPCI. A cQFR value below 0.875 is an independent predictor of both abnormal MVP and long-term mortality. (Prognostic implication of cQFR in STEMI patients; NCT04996901).

ANOCA updated: From pathophysiology to modern clinical practice

Lately, a large number of stable ischemic patients, with no obstructed coronary arteries are being diagnosed. Despite this condition, which is being described as angina with no obstructive coronary arteries (ANOCA), was thought to be benign, recent evidence report that it is associated with increased risk for adverse cardiovascular outcomes. ANOCA is more frequent in women and, pathophysiologically, it is predominantly related with microvascular dysfunction, while other factors, such as endothelial dysfunction, inflammation and autonomic nervous system seem to also play a major role to its development, while other studies implicate ANOCA and microvascular dysfunction in the pathogenesis of heart failure with preserved ejection fraction. For establishing an ANOCA diagnosis, measurement including coronary flow reserve (CFR), microvascular resistance (IMR) and hyperemic microvascular resistance (HMR) are mostly used in clinical practice. In addition, new modalities, such as optical coherence tomography (OCT) are being tested and show promising results for future diagnostic use. Regarding management, pharmacotherapy consists of a wide selection of drugs, according to the respected pathophysiology of the disease (vasospastic angina or microvascular dysfunction), while research for new treatment options including interventional techniques, is currently ongoing. This review, therefore, aims to provide a comprehensive analysis of all aspects related to ANOCA, from pathophysiology to clinical managements, as well as clinical implications and suggestions for future research efforts, which will help advance our understanding of the syndrome and establish more, evidence-based, therapies.

PCSK9 Inhibitors: Is the Time Ripe for the "Fast Track" Use Independently on the LDL-C Baseline Values in Acute Coronary Syndrome?

The low-density lipoprotein cholesterol (LDL-C) lowering decreases the risk to develop major adverse cardiovascular events (MACE) in patients with acute coronary syndrome (ACS). Therefore, the "fast track" use of PCSK9 inhibitors (PCSK9i) has been introduced in ACS patients not achieving LDL-C target (70 mg/dl) despite an ongoing lipid lowering therapy with statin at maximum tolerated dosage plus ezetimibe or stain-naïve (LDL-C > 130 mg/dl). PCSK9i "fast track" use has shown to achieve the regression of "non-culprit" atherosclerotic plaques leading to a further MACE decrease. Interestingly, it has been also hypothesized a role of PCSK9i beyond the LDL-C lowering in ACS. PCSK9i have been demonstrated to decrease the inflammation of atherosclerotic plaques and myocardium, inhibit platelet aggregation, and improve the cardiomyocyte survival against the reperfusion injury. All these findings may positively impact on the prognosis and suggest the PCSK9i use in the acute phase of ACS independently on the baseline LDL-C values.

Empagliflozin Effects in Patients with ST-Elevation Myocardial Infarction Undergoing Primary PCI: The EMI-STEMI Randomized Clinical Trial

INTRODUCTION

Empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, improves cardiovascular outcomes in heart failure patients, but data regarding the efficacy of empagliflozin in the setting of acute myocardial infarction (AMI) is still unclear. The current study aimed to evaluate whether treatment with empagliflozin before primary percutaneous coronary intervention (PCI) improves parameters associated with patients' outcomes.

METHODS

We randomly assigned 101 non-diabetic and non-heart failure patients with ST-elevation myocardial infarction (STEMI) who underwent primary PCI to receive either empagliflozin (10 mg before PCI and once daily for 40 days) or placebo, in addition to the standard treatment. The primary outcomes were changes in left ventricular ejection fraction (LVEF) 40 days after PCI, changes in cardiac troponin I (cTnI) and estimates of its area under the curve (AUC) and the peak level, and resolution of ST-segment in > 50% of leads 90 min after PCI.

RESULTS

No significant difference was observed in terms of the occurrence of ST-segment resolution > 50% (46.0% versus 45.0%; p = 0.92) and the mean level of cTnI at each time point between the two groups. The estimated mean [standard deviation (SD)] AUC of cTnI was 955.0 (595.7) ng h/ml in the intervention and 999.7 (474.7) ng h/ml in the control groups (p = 0.85) without any significant difference in peak cTnI level. The mean (SD) LVEF 40 days after primary PCI was significantly higher in empagliflozin-treated patients than the placebo group [43.2% (5.8%) versus 39.2% (6.7%); p = 0.002].

CONCLUSION

In this study, no significant differences were observed across the groups in terms of cTnI levels and ST-segment resolution in patients with STEMI undergoing primary PCI. However, it shed light on the potential benefits of empagliflozin in improving LVEF following STEMI.

REGISTRATION

Iranian Registry of Clinical Trials Platform ( https://irct.behdasht.gov.ir/ ) identifier number IRCT20111206008307N42.

A simple angio-based coronary flow assessment of culprit vessels in primary percutaneous coronary intervention is associated with long-term prognosis after ST-segment-elevation myocardial infarction

BACKGROUND

Despite prompt reperfusion, the risk of adverse clinical outcomes following ST-segment-elevation myocardial infarction (STEMI) remains pronounced, owing partly to suboptimal reperfusion. However, coronary functional evaluation is seldom feasible during primary percutaneous coronary intervention (PPCI). We aimed to examine the clinical implication of a simple coronary assessment based on single-angiographic view (μQFR) during PPCI in discriminating impaired coronary flow and adverse outcomes for STEMI.

METHODS

STEMI Patients undergoing successful PPCI were enrolled and followed up prospectively from 4 medical centers in China. Post-PPCI μQFR of culprit vessels were analyzed. The primary outcome was major adverse cardiovascular events (MACE), defined as a composite of cardiac death, non-fatal MI, ischemia-driven target-vessel revascularization and readmission for heart failure.

RESULTS

A total of 570 patients with STEMI were enrolled, and post-PCI μQFR was analyzable in 557 (97.7%) patients, with a median of 0.94. Patients with low post-PCI μQFR showed higher incidence of adverse outcomes than those with high μQFR, showing a 2.5-fold increase in the risk for MACE (hazard ratio: 2.51, 95% confidence intervals: 1.33 to 4.72; P = 0.004). Moreover, post-PCI μQFR significantly increased discriminant ability for the occurrence of MACE when added to traditional GRACE risk score for STEMI (integrated discrimination improvement: 0.029; net reclassification index: 0.229; P < 0.05).

CONCLUSIONS

A low μQFR of culprit vessel in PPCI is independently associated with worse clinical outcomes in patients with STEMI. The single-angiographic-view-based coronary evaluation is a feasible tool for discriminating poor prognosis and could serve as a valuable complement in risk stratification for STEMI.

Impact of Coronary Microvascular Dysfunction on Functional Left Ventricular Remodeling and Diastolic Dysfunction

BACKGROUND

Coronary microvascular dysfunction (CMD) is a common complication of ST-segment-elevation myocardial infarction (STEMI) and can lead to adverse cardiovascular events. Whether CMD after STEMI is associated with functional left ventricular remodeling (FLVR) and diastolic dysfunction, has not been investigated.

METHODS AND RESULTS

This is a nonrandomized, observational, prospective study of patients with STEMI with multivessel disease. Coronary flow reserve and index of microcirculatory resistance of the culprit vessel were measured at 3 months post-STEMI. CMD was defined as index of microcirculatory resistance ≥25 or coronary flow reserve <2.0 with a normal fractional flow reserve. We examined the association between CMD, LV diastolic dysfunction, FLVR, and major adverse cardiac events at 12-month follow-up. A total of 210 patients were enrolled; 59.5% were men, with a median age of 65 (interquartile range, 58-76) years. At 3-month follow-up, 57 patients (27.14%) exhibited CMD. After 12 months, when compared with patients without CMD, patients with CMD had poorer LV systolic function recovery (-10.00% versus 8.00%; P<0.001), higher prevalence of grade 2 LV diastolic dysfunction (73.08% versus 1.32%; P<0.001), higher prevalence of group 3 or 4 FLVR (11.32% versus 7.28% and 22.64% versus 1.99%, respectively; P<0.001), and higher incidence of major adverse cardiac events (50.9% versus 9.8%; P<0.001). Index of microcirculatory resistance was independently associated with LV diastolic dysfunction and adverse FLVR.

CONCLUSIONS

CMD is present in ≈1 of 4 patients with STEMI during follow-up. Patients with CMD have a higher prevalence of LV diastolic dysfunction, adverse FLVR, and major adverse cardiac events at 12 months compared with those without CMD.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique Identifier: NCT05406297.

Coronary microvascular obstruction and dysfunction in patients with acute myocardial infarction

Despite prompt epicardial recanalization in patients presenting with ST-segment elevation myocardial infarction (STEMI), coronary microvascular obstruction and dysfunction (CMVO) is still fairly common and is associated with poor prognosis. Various pharmacological and mechanical strategies to treat CMVO have been proposed, but the positive results reported in preclinical and small proof-of-concept studies have not translated into benefits in large clinical trials conducted in the modern treatment setting of patients with STEMI. Therefore, the optimal management of these patients remains a topic of debate. In this Review, we appraise the pathophysiological mechanisms of CMVO, explore the evidence and provide future perspectives on strategies to be implemented to reduce the incidence of CMVO and improve prognosis in patients with STEMI.

Efficacy and safety of intracoronary pro-urokinase combined with low-pressure balloon pre-dilatation during percutaneous coronary intervention in patients with anterior ST-segment elevation myocardial infarction

BACKGROUND

The efficacy and safety of low-pressure balloon pre-dilatation before intracoronary pro-urokinase (pro-UK) in preventing no-reflow during percutaneous coronary intervention (PCI) remains unknown. This study aimed to evaluate the clinical outcomes of intracoronary pro-UK combined with low-pressure balloon pre-dilatation in patients with anterior ST-segment-elevation myocardial infarction (STEMI).

METHODS

This was a randomized, single-blind, investigator-initiated trial that included 179 patients diagnosed with acute anterior STEMI. All patients were eligible for PCI and were randomized into two groups: intracoronary pro-UK combined with (ICPpD group, n = 90) or without (ICP group, n = 89) low-pressure balloon pre-dilatation. The main efficacy endpoint was complete epicardial and myocardial reperfusion. The safety endpoints were major adverse cardiovascular events (MACEs), which were analyzed at 12 months follow-up.

RESULTS

Patients in the ICPpD group presented significantly higher TIMI myocardial perfusion grade 3 (TMPG3) compared to those in the ICP group (77.78% versus 68.54%, P = 0.013), and STR ≥ 70% after PCI 30 min (34.44% versus 26.97%, P = 0.047) or after PCI 90 min (40.0% versus 31.46%, P = 0.044). MACEs occurred in 23 patients (25.56%) in the ICPpD group and in 32 patients (35.96%) in the ICP group. There was no difference in hemorrhagic complications during hospitalization between the groups.

CONCLUSION

Patients with acute anterior STEMI presented more complete epicardial and myocardial reperfusion with adjunctive low-pressure balloon pre-dilatation before intracoronary pro-UK during PCI.

TRIAL REGISTRATION

2019xkj213.

The impact of primary percutaneous coronary intervention strategies during ST-elevation myocardial infarction on the prevalence of coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is a common complication of ST-segment elevation myocardial infarction (STEMI) and can lead to adverse cardiovascular events. This is a non-randomized, observational, prospective study of STEMI patients with multivessel disease who underwent primary PCI, grouped based on whether they underwent balloon pre-dilatation stenting or direct stenting of the culprit lesion. Coronary physiology measurements were performed 3 months post-PCI including coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) measurements at the culprit vessel. The primary endpoint was the prevalence of CMD at 3 months, defined as IMR ≥ 25 or CFR < 2.0 with a normal fractional flow reserve. Secondary endpoints included major adverse cardiovascular events (MACE) at 12 months. Two hundred ten patients were enrolled; most were men, 125 (59.5%), with a median age of 65 years. One hundred twelve (53.2%) underwent balloon pre-dilatation before stenting, and 98 (46.7%) underwent direct stenting. The prevalence of CMD at 3 months was lower in the direct stenting group than in the balloon pre-dilatation stenting group (12.24% vs. 40.18%; p < 0.001). Aspiration thrombectomy and administration of intracoronary glycoprotein IIb/IIIa inhibitors were associated with lower odds of CMD (OR = 0.175, p = 0.001 and OR = 0.113, p = 0.001, respectively). Notably, MACE in patients who underwent direct stenting was lower than in those who underwent balloon pre-dilatation before stenting (14.29% vs. 26.79%; p = 0.040). In STEMI patients with multivessel disease, direct stenting of the culprit lesion, aspiration thrombectomy and administration of intracoronary glycoprotein IIb/IIIa inhibitors were associated with a lower prevalence of CMD at 3 months and lower incidence of MACE at 12 months compared with balloon pre-dilatation stenting.This trial is registered at https://ichgcp.net/clinical-trials-registry/NCT05406297 .

Angio-based coronary functional assessment predicts 30-day new-onset heart failure after acute myocardial infarction

AIMS

Suboptimal perfusion leading to heart failure (HF) often occurs after ST-segment elevation myocardial infarction (STEMI), despite restoration of epicardial coronary flow in primary percutaneous coronary intervention (PPCI) era. We determined the clinical implications of angio-based coronary functional assessment in evaluation of suboptimal perfusion and further outcomes among STEMI patients after successful PPCI.

METHODS AND RESULTS

In this study, STEMI patients in the Chinese STEMI PPCI registry trial (NCT04996901) who achieved post-PPCI thrombolysis in myocardial infarction grade 3 flow were retrospectively screened. Post-procedural quantitative flow ratio (QFR), angio-based microvascular resistance (AMR), and coronary flow velocity (CFV) of the infarct-related artery were calculated. QFR and AMR measure epicardial stenosis severity and microvascular resistance, respectively. QFR+ was defined as QFR < 0.90 while QFR- was QFR ≥ 0.90. AMR+ was defined as AMR ≥ 250 mmHg*s/m while AMR- was AMR < 250 mmHg*s/m. The primary outcome was 30-day new-onset HF. The Kaplan-Meier curves were used to establish the associations between QFR, AMR, CFV, and HF incidences. The relationship between CFV and combined QFR and AMR indices was further assessed. Independent predictors were determined using Cox regression analysis. The receiver-operating characteristic curve was used to assess discriminant ability to predict HF. A total of 942 patients (mean age was 57.8 ± 11.7 years and 84.6% were men) were enrolled. Among them, 129 patients had new-onset HF episodes. Patients in the QFR-/AMR- group had a low risk of HF compared with those in the QFR+/AMR+ group (10.5% vs. 27.3%, P = 0.027). A higher CFV ≥ 17.4 cm/s was associated with low HF incidences as compared with CFV < 17.4 cm/s (10.3% vs. 16.8%, P = 0.005), whereas isolated QFR or AMR did not reveal any marked differences in HF incidences (P = 0.150 and 0.079, respectively). The highest and lowest medians of CFV were observed in the QFR-/AMR- and QFR+/AMR+ groups, respectively. CFV correlated well with the QFR/AMR ratio (adjusted R2  = 1, P < 0.001) and post-PPCI CFV was found to be an independent predictor of post-STEMI HF (adjusted hazard ratio: 0.61, 95% confidence interval: 0.41-0.90, P = 0.012). The area under curve estimate of the multivariable regression model was 0.749.

CONCLUSIONS

CFV is an integrated coronary physiological assessment approach that incorporates epicardial and microcirculatory contributions. Patients with post-PPCI CFV < 17.4 cm/s were strongly associated with a high risk for post-STEMI HF, even achieving thrombolysis in myocardial infarction grade 3 flow. The immediate angio-based coronary functional assessment is a feasible tool for evaluating suboptimal perfusion and risk stratification.

Coronary Microvascular Dysfunction: What Clinicians and Investigators Should Know

PURPOSE OF REVIEW

Abnormal structure and function of the coronary microvasculature have been implicated in the pathophysiology of multiple cardiovascular disease processes. This article reviews recent research progress related to coronary microvascular dysfunction (CMD) and salient clinical takeaways.

RECENT FINDINGS

CMD is prevalent in patients with signs and symptoms of ischemia and no obstructive epicardial coronary artery disease (INOCA), particularly in women. CMD is associated with adverse outcomes, including most frequently the development of heart failure with preserved ejection fraction. It is also associated with adverse outcomes in patient populations including hypertrophic cardiomyopathy, dilated cardiomyopathy, and acute coronary syndromes. In patients with INOCA, stratified medical therapy guided by invasive coronary function testing to define the subtype of CMD leads to improved symptoms. There are invasive and non-invasive methodologies to diagnose CMD that provide prognostic information and mechanistic information to direct treatment. Available treatments improve symptoms and myocardial blood flow; ongoing investigations aim to develop therapy to improve adverse outcomes related to CMD.

Coronary Microcirculation: The Next Frontier in the Management of STEMI

Although the widespread adoption of timely invasive reperfusion strategies over the last two decades has significantly improved the prognosis of patients with ST-segment elevation myocardial infarction (STEMI), up to half of patients after angiographically successful primary percutaneous coronary intervention (PCI) still have signs of inadequate reperfusion at the level of coronary microcirculation. This phenomenon, termed coronary microvascular dysfunction (CMD), has been associated with impaired prognosis. The aim of the present review is to describe the collected evidence on the occurrence of CMD following primary PCI, means of assessment and its association with the infarct size and clinical outcomes. Therefore, the practical role of invasive assessment of CMD in the catheterization laboratory, at the end of primary PCI, is emphasized, with an overview of available technologies including thermodilution- and Doppler-based methods, as well as recently developing functional coronary angiography. In this regard, we review the conceptual background and the prognostic value of coronary flow reserve (CFR), index of microcirculatory resistance (IMR), hyperemic microvascular resistance (HMR), pressure at zero flow (PzF) and angiography-derived IMR. Finally, the so-far investigated therapeutic strategies targeting coronary microcirculation after STEMI are revisited.

Practical Approach to Diagnosis, Prevention, and Management of Coronary No-Reflow

Coronary no-reflow (NR) defined as inadequate myocardial perfusion despite restoration of coronary artery patency is a bane for an interventional cardiologist. It can complicate percutaneous coronary interventions especially in the setting of STEMI and dampens the potential benefits of PPCI. Broadly classified as Reperfusion NR and Interventional NR, mechanism is multifactorial. The basic underlying culprit is microvascular obstruction either secondary to distal embolization, intravascular plugging, or ischemic reperfusion injury. Coronary angiogram is an easy, readily available, and essential modality to diagnose no-reflow, but the gold standard is gadolinium-enhanced cardiovascular magnetic resonance imaging. Preventive strategies for NR should be integral part of prePCI planning especially in clinical scenario where NR is expected such as STEMI with delayed presentation and high thrombus burden, atherectomy, and SVG PCI. The cornerstone of treatment for NR is local vasodilators and antiplatelet therapy to ameliorate vasospasm and thromboembolism respectively, and different combinations of the two should be used in no specific order to achieve reversal of NR. NR phenomenon is associated with poor short-term and long-term prognosis and every attempt should be made to avoid or reverse it. Therapeutic hypothermia, hyperoxemic reperfusion therapy, targeted anti-inflammatory approach, and cellular approach appear proising but further research is mandatory.

Microcirculation function assessment in acute myocardial infarction: A systematic review of microcirculatory resistance indices

BACKGROUND

Up to 50% of acute myocardial infarction (MI) patients present with microvascular dysfunction, after a successful percutaneous coronary intervention (PCI), which leads to worse clinical outcomes. The main purpose of this study is to provide a critical appraisal of the emerging role of invasive microvascular resistance indices in the MI setting, using the index of microcirculatory resistance (IMR), hyperemic microvascular resistance (HMR) and zero-flow pressure (Pzf).

METHODS

We systematically explored relevant studies in the context of MI that correlated microcirculation resistance indices with microvascular dysfunction on cardiac magnetic resonance (CMR), microvascular dysfunction occurring in infarct related arteries (IRA) and non-IRA and its relation to clinical outcomes.

RESULTS

The microcirculation resistance indices correlated significantly with microvascular obstruction (MVO) and infarct size (IS) on CMR. Although HMR and Pzf seem to have better diagnostic accuracy for MVO and IS, IMR has more validation data. Although, both IMR and HMR were independent predictors of adverse cardiovascular events, HMR has no validated cut-off value and data is limited to small observational studies. The presence of microvascular dysfunction in non-IRA does not impact prognosis.

CONCLUSION

Microvascular resistance indices are valuable means to evaluate microcirculation function following MI. Microvascular dysfunction relates to the extent of myocardial damage and clinical outcomes after MI.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021228432], identifier [CRD42021228432].

The Dynamic Relationship Between Invasive Microvascular Function and Microvascular Injury Indicators, and Their Association With Left Ventricular Function and Infarct Size at 1-Month After Reperfused ST-Segment-Elevation Myocardial Infarction

BACKGROUND

The invasive microvascular function indices, coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR), exhibit a dynamic pattern after ST-segment-elevation myocardial infarction. The effects of microvascular injury on the evolution of the microvascular function and the prognostic significance of the evolution of microvascular function are unknown. We investigated the relationship between the temporal changes of CFR and IMR, and cardiovascular magnetic resonance-derived microvascular injury characteristics in reperfused ST-segment-elevation myocardial infarction patients, and their association with 1-month left ventricular ejection fraction and infarct size (IS).

METHODS

In 109 ST-segment-elevation myocardial infarction patients who underwent angiography for primary percutaneous coronary intervention (PPCI) and at 1-month follow-up, invasive assessment of CFR and IMR were performed in the culprit artery during both procedures. Cardiovascular magnetic resonance was performed 2 to 7 days after PPCI and at 1 month and provided assessment of left ventricular ejection fraction, IS, microvascular obstruction, and intramyocardial hemorrhage.

RESULTS

CFR and IMR significantly changed over 1 month (both, P<0.001). The absolute IMR change over 1 month (ΔIMR) showed association with both microvascular obstruction and intramyocardial hemorrhage presence (both, P=0.01). ΔIMR differed between patients with/without microvascular obstruction (P=0.02) and with/without intramyocardial hemorrhage (P=0.04) but not ΔCFR for both. ΔIMR demonstrated association with both left ventricular ejection fraction and IS at 1 month (P<0.001, P=0.001, respectively), but not ΔCFR for both. Receiver-operating characteristics curve analysis of ΔIMR showed a larger area under the curve than post-PPCI CFR and IMR, and ΔCFR to be associated with both 1-month left ventricular ejection fraction >50% and extensive IS (the highest quartile).

CONCLUSIONS

In reperfused ST-segment-elevation myocardial infarction patients, CFR and IMR significantly improved 1 month after PPCI; the temporal change in IMR is closely related to the presence/absence of microvascular damage and IS. ΔIMR exhibits a stronger association for 1-month functional outcome than post-PPCI CFR, IMR, or ΔCFR.

Culprit Lesion Morphology of Rapidly Progressive and Extensive Anterior-Wall ST-Segment Elevation Myocardial Infarction

BACKGROUND

Rapidly progressive, extensive myocardial injury/infarction (RPEMI) beyond the concept of wave-front phenomenon can be observed even when achieving timely reperfusion; however, the pathogenesis of RPEMI remains unknown. This retrospective study investigated clinical and lesion characteristics of RPEMI, focusing on culprit-lesion morphology (CLM).

METHODS

Among patients with extensive anterior-wall ST-segment elevation myocardial infarction due to proximal left anterior descending artery lesions who had reperfusion within 3 hours of symptom onset, 60 patients undergoing both intravascular ultrasound and cardiac magnetic resonance imaging were enrolled. Myocardial injury/infarction before reperfusion therapy was assessed by QRS scores at hospitalization electrocardiogram, and the extent of myocardial injury/infarction was evaluated by cardiac magnetic resonance imaging, which measured area at risk, infarct size, myocardial salvage index, microvascular obstruction, and left ventricular ejection fraction. RPEMI was defined as lower left ventricular ejection fraction (less median value) with microvascular obstruction.

RESULTS

Despite comparable onset-to-door and onset-to-reperfusion times and area at risk, patients with RPEMI showed higher QRS scores at hospitalization (5 [4.3-6] versus 3 [2-4], P<0.001) and infarct size (26.5±9.1 versus 20.4±10.5%, P=0.04), and a tendency toward lower myocardial salvage index (0.27±0.14 versus 0.36±0.20, P=0.10) compared with those without. Patients with versus without RPEMI more frequently observed specific CLM on intravascular ultrasound, characterized by the combination of vulnerable plaques, plaque ruptures, and/or large thrombi. When stratified by CLM-score composed of these 3 criteria, higher CLM-scores were or tended to be associated with higher QRS scores and incidence of RPEMI. In multivariate analyses including no-reflow phenomenon and final coronary-flow deterioration, increased CLM-score (≥2) was independently associated with high QRS scores and RPEMI (odd ratio 11.25 [95% CI, 2.43-52.00]; P=0.002).

CONCLUSIONS

Vulnerable CLM was a consistent determinant of advanced myocardial injury/infarction both before and after reperfusion therapy and may play a pivotal role in the development of RPEMI.

"No-Reflow" Phenomenon: A Contemporary Review

Primary percutaneous angioplasty (pPCI), represents the reperfusion strategy of choice for patients with STEMI according to current international guidelines of the European Society of Cardiology. Coronary no-reflow is characterized by angiographic evidence of slow or no anterograde epicardial flow, resulting in inadequate myocardial perfusion in the absence of evidence of mechanical vessel obstruction. No reflow (NR) is related to a functional and structural alteration of the coronary microcirculation and we can list four main pathophysiological mechanisms: distal atherothrombotic embolization, ischemic damage, reperfusion injury, and individual susceptibility to microvascular damage. This review will provide a contemporary overview of the pathogenesis, diagnosis, and treatment of NR.

Value of Fast MVO Identification From Contrast-Enhanced Cine (CE-SSFP) Combined With Myocardial Strain in Predicting Adverse Events in Patients After ST-Elevation Myocardial Infarction

OBJECTIVES

Cardiac magnetic resonance imaging (CMR) can be used for a one-step evaluation of myocardial function and pathological features after acute ST-elevation myocardial infarction (STEMI). We aimed to evaluate the value of fast microvascular occlusion (MVO) identification from contrast-enhanced steady-state free precession (CE-SSFP) combined with myocardial strain in predicting major cardiovascular adverse events (MACEs) in primary percutaneous coronary intervention (pPCI) patients with STEMI.

METHODS

In total, 237 patients with STEMI who received pPCI and completed CMR scans within the following week were enrolled, MVO identification and the myocardial strain analysis were performed in CE-SSFP images without an additional method. The primary endpoint was the presence of MACE, which is defined as a composite of death, reinfarction, and congestive heart failure (HF).

RESULTS

After 13 months of follow-up [interquartile range (IQR): 11-24], 30 patients (14%) developed MACE; the MVO (hazard ratio (HR) was 3.10; 95% CI: 1.14-8.99, p = 0.028), and the infarct size (IS) (HR: 1.03; 95% CI: 1.0-1.06, p = 0.042) and global longitudinal strain (GLS) (HR: 1.08; 95% CI: 1.01-1.17, p = 0.029) were finally associated with MACE. Receiver operating characteristic (ROC) analyses show that the area under the curve (AUC) of GLS was large (0.73 [95% CI, 0.63-0.82], p = 0.001), and the best cut-off was -11.8%, with 76.7% sensitivity and 58.9% specificity, which are greater than those of IS (0.70, 95% CI, 0.60-0.81, p < 0.001) and MVO (0.68, 95% CI, 0.58-0.78, p < 0.001). However, combining MVO and GLS resulted in a much greater finding (AUC = 0.775, 95% CI: 0.727-0.824, p < 0.001) and better sensitivity and specificity (83.3%, 66.5%).

CONCLUSION

Microvascular occlusion identification from contrast-enhanced cine combined with myocardial strain could be a quick and reliable option for patients with STEMI who underwent pPCI; it correlates well with the prognosis of patients with STEMI in terms of MACE.

Intravenous nicorandil during primary percutaneous coronary intervention in patients with ST-Elevation myocardial infarction: Rationale and design of the Clinical Efficacy and Safety of Intravenous Nicorandil (CLEAN) trial

BACKGROUND

The efficacy and safety of intravenous infusion of nicorandil during primary percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI) remain uncertain.

OBJECTIVES

The primary objective of the CLinical Efficacy and sAfety of intravenous Nicorandil (CLEAN) trial is to evaluate the long-term efficacy and safety of intravenous administration of nicorandil as adjuncts to reperfusion therapy in patients with STEMI undergoing primary PCI.

DESIGN

The CLEAN trial is a multicenter, randomized, double-blind, placebo-controlled trial that will enroll 1,500 patients from 40 centers across china. patients were randomly (1:1) assigned to receive intravenous nicorandil (6 mg as a bolus before reperfusion, followed by 48 hours of continuous infusion at a dose of 6 mg/h after coronary intervention) or the same dose of placebo according to randomization. The primary efficacy outcome was a composite of death from cardiovascular causes, nonfatal myocardial infarction, target vessel revascularization, and unplanned hospitalization for heart failure within 12 months. The secondary efficacy outcomes included the individual components of the combined efficacy endpoint, incidence of slow coronary flow after PCI, and incidence of complete ST-segment resolution at 2 hours after PCI. the safety outcomes included the incidence of hypotension after drug infusion and other adverse events during medication.

SUMMARY

CLEAN will determine whether the addition of intravenous nicorandil as adjuncts to reperfusion therapy reduces the major adverse cardiovascular events in STEMI patients undergoing primary PCI.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04665648.

The Index of Microcirculatory Resistance after Primary Percutaneous Coronary Intervention Predicts Long-Term Clinical Outcomes in Patients with ST-Segment Elevation Myocardial Infarction

The index of microcirculatory resistance (IMR) is a simple method that can measure microvascular function after primary percutaneous coronary intervention (PCI) in patients with ST-segment Elevation Myocardial Infarction (STEMI). This study is to find out whether IMR predicts clinical long-term outcomes in STEMI patients. A total of 316 patients with STEMI who underwent primary PCI from 2005 to 2015 were enrolled. The IMR was measured using pressure sensor/thermistor-tipped guidewire after primary PCI. The primary endpoint was the rate of death or hospitalization for heart failure (HF) over a mean follow-up period of 65 months. The mean corrected IMR was 29.4 ± 20.0. Patients with an IMR > 29 had a higher rate of the primary endpoint compared to patients with an IMR ≤ 29 (10.3% vs. 2.1%, p = 0.001). During the follow-up period, 13 patients (4.1%) died and 6 patients (1.9%) were hospitalized for HF. An IMR > 29 was associated with an increased risk of death or hospitalization for HF (OR 5.378, p = 0.004). On multivariable analysis, IMR > 29 (OR 3.962, p = 0.022) remained an independent predictor of death or hospitalization for HF with age (OR 1.048, p = 0.049) and symptom-to-balloon time (OR 1.002, p = 0.049). High IMR was an independent predictor for poor long-term clinical outcomes in STEMI patients after primary PCI.

Effects of Intracoronary Pro-urokinase or Tirofiban on Coronary Flow During Primary Percutaneous Coronary Intervention for Acute Myocardial Infarction: A Multi-Center, Placebo-Controlled, Single-Blind, Randomized Clinical Trial

Background: To determine whether intracoronary pro-urokinase or tirofiban improves myocardial reperfusion during primary percutaneous coronary intervention (PCI) for acute ST-segment elevation myocardial infarction (STEMI).

Methods: The study included patients with acute STEMI presenting within 12 h of symptoms at 11 hospitals in China between November 2015 and July 2017. Patients were randomized to receive selective intracoronary infusion of recombinant pro-urokinase (20 mg), tirofiban (10 μg/kg), or saline (20 mL) proximal to the infarct-related lesion over a 3-min period before stent implantation during primary PCI. The primary outcome was final corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) after PCI.

Results: This study included 345 patients. Initial angiography identified a high-grade thrombus (TIMI 4–5) in 80% of patients. Final CTFC after PCI was significantly lower in the pro-urokinase (P < 0.001) and tirofiban (P < 0.001) groups than in the saline group and similar between the pro-urokinase and tirofiban groups (P > 0.05). The pro-urokinase (P = 0.008) and tirofiban groups (P = 0.022) had more complete ST-segment resolution at 2 h and lower peak creatine kinase-MB levels after PCI than the saline group (P = 0.006 and P = 0.023). The 30-day incidence of major adverse cardiac events was 4.5% in the pro-urokinase group, 3.4% in the tirofiban group, and 2.6% in the saline group. The incidence of in-hospital TIMI major bleeding events was low and comparable between groups.

Conclusions: Adjunctive intracoronary pro-urokinase or tirofiban given before stent implantation during primary PCI improves myocardial reperfusion without increasing the incidence of major bleeding events.

The Predictive Value of Baseline Target Lesion SYNTAX Score for No-Reflow during Urgent Percutaneous Coronary Intervention in Acute Myocardial Infarction

OBJECTIVES

To evaluate the predictive value of target lesion SYNTAX score (TL-SS) for no-reflow in the patients with acute myocardial infarction undergoing urgent percutaneous coronary intervention (PCI).

BACKGROUND

Risk assessment, prevention, and prompt management of no-reflow in urgent PCI are crucial but remain challenging. SYNTAX score emerged as a tool for prediction, but may contain redundant information.

METHODS

After screening of consecutive patients who underwent urgent PCI in Fuwai Hospital from January 2013 to December 2013, 487 patients with 528 lesions were involved. The endpoint was no-reflow during the PCI procedure.

RESULTS

No-reflow occurred in 52 patients (10.7%) and 53 lesions (10.0%). High TL-SS levels were strongly associated with increased risks of no-reflow in the urgent PCI procedure (all adjusted P < 0.05). TL-SS displayed good discrimination ability for no-reflow (C-statistics = 0.76, 95% CI 0.72-0.80), which was better than that of SYNTAX score (P=0.016). Following categorizing the lesions into two groups according to the Youden Index, the high-risk group (TL-SS ≥8) showed significantly higher no-reflow rate compared with the low-risk group (TL-SS <8) (20.6% vs. 3.6%, odds ratio 6.86, 95% confidence interval 3.50-13.41, P < 0.001). In the target lesions that underwent balloon predilation, maximum predilation pressure >10 atm was associated with higher rate of no-reflow in the high-risk group (odds ratio 3.81, 95% confidence interval 1.10-13.17).

CONCLUSIONS

TL-SS is a potential predictor for risk stratification of no-reflow in urgent PCI. In the high TL-SS lesions that underwent balloon predilation, maximum predilation pressure >10 atm was associated with higher risk of no-reflow.

Coronary Microvascular Dysfunction

Many patients with chest pain undergoing coronary angiography do not show significant obstructive coronary lesions. A substantial proportion of these patients have abnormalities in the function and structure of coronary microcirculation due to endothelial and smooth muscle cell dysfunction. The coronary microcirculation has a fundamental role in the regulation of coronary blood flow in response to cardiac oxygen requirements. Impairment of this mechanism, defined as coronary microvascular dysfunction (CMD), carries an increased risk of adverse cardiovascular clinical outcomes. Coronary endothelial dysfunction accounts for approximately two-thirds of clinical conditions presenting with symptoms and signs of myocardial ischemia without obstructive coronary disease, termed "ischemia with non-obstructive coronary artery disease" (INOCA) and for a small proportion of "myocardial infarction with non-obstructive coronary artery disease" (MINOCA). More frequently, the clinical presentation of INOCA is microvascular angina due to CMD, while some patients present vasospastic angina due to epicardial spasm, and mixed epicardial and microvascular forms. CMD may be associated with focal and diffuse epicardial coronary atherosclerosis, which may reinforce each other. Both INOCA and MINOCA are more common in females. Clinical classification of CMD includes the association with conditions in which atherosclerosis has limited relevance, with non-obstructive atherosclerosis, and with obstructive atherosclerosis. Several studies already exist which support the evidence that CMD is part of systemic microvascular disease involving multiple organs, such as brain and kidney. Moreover, CMD is strongly associated with the development of heart failure with preserved ejection fraction (HFpEF), diabetes, hypertensive heart disease, and also chronic inflammatory and autoimmune diseases. Since coronary microcirculation is not visible on invasive angiography or computed tomographic coronary angiography (CTCA), the diagnosis of CMD is usually based on functional assessment of microcirculation, which can be performed by both invasive and non-invasive methods, including the assessment of delayed flow of contrast during angiography, measurement of coronary flow reserve (CFR) and index of microvascular resistance (IMR), evaluation of angina induced by intracoronary acetylcholine infusion, and assessment of myocardial perfusion by positron emission tomography (PET) and magnetic resonance (CMR).

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.

Pathophysiology and diagnosis of coronary microvascular dysfunction in ST-elevation myocardial infarction

Early mechanical reperfusion of the epicardial coronary artery by primary percutaneous coronary intervention (PCI) is the guideline-recommended treatment for ST-elevation myocardial infarction (STEMI). Successful restoration of epicardial coronary blood flow can be achieved in over 95% of PCI procedures. However, despite angiographically complete epicardial coronary artery patency, in about half of the patients perfusion to the distal coronary microvasculature is not fully restored, which is associated with increased morbidity and mortality. The exact pathophysiological mechanism of post-ischaemic coronary microvascular dysfunction (CMD) is still debated. Therefore, the current review discusses invasive and non-invasive techniques for the diagnosis and quantification of CMD in STEMI in the clinical setting as well as results from experimental in vitro and in vivo models focusing on ischaemic-, reperfusion-, and inflammatory damage to the coronary microvascular endothelial cells. Finally, we discuss future opportunities to prevent or treat CMD in STEMI patients.

Lancaster G, W. Zarich S. Invasive Evaluation of the Microvasculature in Acute Myocardial Infarction: Coronary Flow Reserve versus the Index of Microcirculatory Resistance

Acute myocardial infarction (AMI) is one of the most common causes of death in both the developed and developing world. It has high associated morbidity despite prompt institution of recommended therapy. The focus over the last few decades in ST-segment elevation AMI has been on timely reperfusion of the epicardial vessel. However, microvascular consequences after reperfusion, such as microvascular obstruction (MVO), are equally reliable predictors of outcome. The attention on the microcirculation has meant that traditional angiographic/anatomic methods are insufficient. We searched PubMed and the Cochrane database for English-language studies published between January 2000 and November 2019 that investigated the use of invasive physiologic tools in AMI. Based on these results, we provide a comprehensive review regarding the role for the invasive evaluation of the microcirculation in AMI, with specific emphasis on coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR).

The coronary circulation in acute myocardial ischaemia/reperfusion injury: a target for cardioprotection

The coronary circulation is both culprit and victim of acute myocardial infarction. The rupture of an epicardial atherosclerotic plaque with superimposed thrombosis causes coronary occlusion, and this occlusion must be removed to induce reperfusion. However, ischaemia and reperfusion cause damage not only in cardiomyocytes but also in the coronary circulation, including microembolization of debris and release of soluble factors from the culprit lesion, impairment of endothelial integrity with subsequently increased permeability and oedema formation, platelet activation and leucocyte adherence, erythrocyte stasis, a shift from vasodilation to vasoconstriction, and ultimately structural damage to the capillaries with eventual no-reflow, microvascular obstruction (MVO), and intramyocardial haemorrhage (IMH). Therefore, the coronary circulation is a valid target for cardioprotection, beyond protection of the cardiomyocyte. Virtually all of the above deleterious endpoints have been demonstrated to be favourably influenced by one or the other mechanical or pharmacological cardioprotective intervention. However, no-reflow is still a serious complication of reperfused myocardial infarction and carries, independently from infarct size, an unfavourable prognosis. MVO and IMH can be diagnosed by modern imaging technologies, but still await an effective therapy. The current review provides an overview of strategies to protect the coronary circulation from acute myocardial ischaemia/reperfusion injury. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Cardiovascular Magnetic Resonance in Acute ST-Segment-Elevation Myocardial Infarction: Recent Advances, Controversies, and Future Directions

Although mortality after ST-segment elevation myocardial infarction (MI) is on the decline, the number of patients developing heart failure as a result of MI is on the rise. Apart from timely reperfusion by primary percutaneous coronary intervention, there is currently no established therapy for reducing MI size. Thus, new cardioprotective therapies are required to improve clinical outcomes after ST-segment-elevation MI. Cardiovascular magnetic resonance has emerged as an important imaging modality for assessing the efficacy of novel therapies for reducing MI size and preventing subsequent adverse left ventricular remodeling. The recent availability of multiparametric mapping cardiovascular magnetic resonance imaging has provided new insights into the pathophysiology underlying myocardial edema, microvascular obstruction, intramyocardial hemorrhage, and changes in the remote myocardial interstitial space after ST-segment-elevation MI. In this article, we provide an overview of the recent advances in cardiovascular magnetic resonance imaging in reperfused patients with ST-segment-elevation MI, discuss the controversies surrounding its use, and explore future applications of cardiovascular magnetic resonance in this setting.

Mineralocorticoid receptor antagonist pre-treatment and early post-treatment to minimize reperfusion injury after ST-elevation myocardial infarction: The MINIMIZE STEMI trial

Background

Mineralocorticoid receptor antagonist (MRA) therapy has been shown to prevent adverse left ventricular (LV) remodeling in ST-segment elevation myocardial infarction (STEMI) patients with heart failure. Whether initiating MRA therapy prior to primary percutaneous coronary intervention (PPCI) accrues additional benefit of reducing myocardial infarct size and preventing adverse LV remodeling is not known. We aimed to investigate whether MRA therapy initiated prior to reperfusion reduces myocardial infarct (MI) size and prevents adverse LV remodeling in STEMI patients.

Methods

STEMI patients presenting within 12 hours and with a proximal coronary artery occlusion with Thrombolysis In Myocardial Infarction flow grade 0 were consented and randomized to either an intravenous bolus of potassium canrenoate, followed by oral spironolactone for 3 months or matching placebo. The primary endpoint was MI size by cardiovascular magnetic resonance at 3 months.

Results

Sixty-seven patients completed the study. There was no significant difference in the final MI size at 3 months between the 2 groups (placebo: 17 ± 11%, MRA: 16 ± 10%, P = .574). There was also no difference in acute MI size (26 ± 16% versus 23 ± 14%, P = .425) or myocardial salvage (26 ± 12% versus 24 ± 8%, P = .456). At follow-up, there was a trend towards an improvement in LVEF (placebo: 49 ± 8%, MRA: 54 ± 11%, P = .053), and the MRA group had significantly greater percentage decrease in LVEDV (mean difference: −12.2 (95% CI −20.3 to −4.4)%, P = .003) and LVESV (mean difference: −18.2 (95% CI −30.1 to −6.3)%, P = .003).

Conclusion

This pilot study showed no benefit of MRA therapy in reducing MI size in STEMI patients when initiated prior to reperfusion, but there was an improvement in LV remodeling at 3 months. Adequately powered studies are warranted to confirm these findings.

Index of Microcirculatory Resistance as a Tool to Characterize Microvascular Obstruction and to Predict Infarct Size Regression in Patients With STEMI Undergoing Primary PCI

OBJECTIVES

This study aimed to compare the value of the index of microcirculatory resistance (IMR) and microvascular obstruction (MVO) measured by cardiac magnetic resonance (CMR) in patients treated for and recovering from ST-segment elevation myocardial infarction.

BACKGROUND

IMR can identify patients with microvascular dysfunction acutely after primary percutaneous coronary intervention (pPCI), and a threshold of >40 has been shown to be associated with an adverse clinical outcome. Similarly, MVO is recognized as an adverse feature in patients with ST-segment elevation myocardial infarction. Even though both IMR and MVO reflect coronary microvascular status, the interaction between these 2 parameters is uncertain.

METHODS

A total of 110 patients treated with pPCI were included, and IMR was measured immediately at completion of pPCI. Infarct size (IS) as a percentage of left ventricular mass was quantified at 48 h (38.4 ± 12.0 h) and 6 months (194.0 ± 20.0 days) using CMR. MVO was identified and quantified at 48 h by CMR.

RESULTS

Overall, a discordance between IMR and MVO was observed in 36.7% of cases, with 31 patients having MVO and IMR ≤40. Compared with patients with MVO and IMR ≤40, patients with both MVO and IMR >40 had an 11.9-fold increased risk of final IS >25% at 6 months (p = 0.001). Patients with MVO and IMR ≤40 had a significantly smaller IS at 6 months (p = 0.001), with significant regression in IS over time (34.4% [interquartile range (IQR): 27.3% to 41.0%] vs. 22.3% [IQR: 16.0% to 30.0%]; p = 0.001).

CONCLUSIONS

Discordant prognostic information was obtained from IMR and MVO in nearly one-third of cases; however, IMR can be helpful in grading the degree and severity of MVO.

Nicorandil prior to primary percutaneous coronary intervention improves clinical outcomes in patients with acute myocardial infarction: a meta-analysis of randomized controlled trials

Background: Nicorandil prior to reperfusion by primary percutaneous coronary intervention (PCI) in patients with ST-segment elevated myocardial infarction (STEMI) has been suggested to be beneficial. However, results of previous randomized controlled trials (RCTs) were not consistent. We aimed to perform a meta-analysis to systematically evaluate the effect of periprocedural nicorandil in these patients. Methods: Related studies were obtained by searching PubMed, Embase and Cochrane's Library. Effects of perioperative nicorandil on the incidence of no-reflow phenomenon (NRP), corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC), wall motion score (WMS), left ventricular ejection fraction (LVEF), heart failure (HF) exacerbation of rehospitalization and incidence of major cardiovascular adverse events (MACE) were analyzed. Results: Eighteen RCTs with 2,055 patients were included. Treatment of nicorandil prior to PCI significantly reduced the incidence of NRP (risk ratio [RR]: 0.47, P<0.001), and reduced CTFC (weighed mean difference [WMD]: -4.54, P<0.001) immediately after PCI. Moreover, although nicorandil did not significantly affect WMS (WMD: 0.04, P=0.91), treatment of nicorandil significantly increased LVEF in STEMI patients undergoing primary PCI (WMD: 1.89%, P<0.001). In addition, nicorandil significantly reduced the risk of HF exacerbation or rehospitalization (RR: 0.44, P=0.001) and the incidence of MACE (RR: 0.68, P<0.001). Further analyses showed that effects of nicorandil on LVEF, HF exacerbation and MACE were consistent within one month after PCI and during follow-up. Conclusions: Periprocedural nicorandil improves coronary blood flow, cardiac systolic function and prognosis in STEMI patients receiving primary PCI.

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

INTRODUCTION

Microvascular dysfunction in the setting of acute ST-segment elevation myocardial infarction (STEMI) is an indicator of poor long-term prognosis. Prompt assessment and pharmacological or procedural therapy (prophylactic or post onset of dysfunction) may improve outcomes in STEMI post-primary percutaneous intervention. Areas covered: The aim of this review is to provide a comprehensive analysis of the evidence available about the assessment and management of coronary microcirculatory injury/dysfunction in STEMI. We also aim to elucidate the possible strategies that could be applied in clinical practice to support the application of already available or novel therapeutic strategies for the prevention and management of microvascular impairment. Expert commentary: There are multiple established methods in assessing microvascular dysfunction, both non-invasively and invasively. Invasive physiological measurements allow real-time assessment of microvascular dysfunction and have prognostic cut-off values. Multiple therapeutic modalities exist for both preventing and treating microvascular dysfunction. These can be either pharmacological or mechanical, and there is no algorithm to guide if, how and when to apply them. Future research into both procedural and pharmacological therapy guided by physiological measurements is needed, with the aim of recognizing high-risk patients who would benefit from therapy.

Coronary Microvascular Disease Pathogenic Mechanisms and Therapeutic Options: JACC State-of-the-Art Review

Coronary microvascular disease (CMD) refers to the subset of disorders affecting the structure and function of the coronary microcirculation, is prevalent in patients across a broad spectrum of cardiovascular risk factors, and is associated with an increased risk of adverse events. Contemporary evidence supports that most patients with CMD also have macrovessel atherosclerosis, which has important implications for their prognosis and management. In this state-of-the-art review, the authors summarize the pathophysiology of CMD, provide an update of diagnostic testing strategies, and classify CMD into phenotypes according to severity and coexistence with atherosclerosis. They examine emerging data highlighting the significance of CMD in specific populations, including obesity and insulin resistance, myocardial injury and heart failure with preserved ejection fraction, and nonobstructive and obstructive coronary artery disease. Finally, they discuss the role of CMD as a potential target for novel interventions beyond conventional approaches, representing a new frontier in cardiovascular disease reduction.

Deferred vs Immediate Stenting in Primary Percutaneous Coronary Intervention: A Collaborative Meta-analysis of Randomized Trials With Cardiac Magnetic Resonance Imaging Data

BACKGROUND

The role of deferred vs immediate stenting during primary percutaneous coronary intervention (PCI) for patients with ST-segment elevation myocardial infarction (STEMI) remains controversial.

METHODS

We undertook a collaborative meta-analysis of study-level data by searching electronic scientific databases for investigations of primary PCI patients randomized to deferred or immediate stenting and subsequent cardiac magnetic resonance imaging. Primary angiographic and imaging outcomes were slow/no-reflow and microvascular obstruction (MVO), respectively. Main secondary outcome was recurrent ischemia.

RESULTS

Among 4 trials, a total of 1570 patients with STEMI were assigned to primary PCI with either deferred (n = 779) or immediate stenting (n = 791). Of these, 797 participants had analyzable cardiac magnetic resonance imaging examinations. Median clinical follow-up was 9 months. Patients treated with deferred stenting showed a lower risk of developing slow/no-reflow in the culprit vessel (risk ratio [RR], 0.54 [95% confidence interval (CI), 0.41-0.72]; P < 0.001), a similar risk for MVO (RR, 0.93 [95% CI, 0.76-1.14]; P = 0.51), and trended higher in the risk of recurrent ischemia (RR, 2.42 [95% CI, 0.88-6.63]; P = 0.09) compared with those treated with immediate stenting. The treatment effect for slow/no-reflow and MVO correlated with a thrombus score grade > 3 at the baseline angiography and with the total stent length implanted in the culprit artery.

CONCLUSIONS

A strategy of deferred stenting during primary PCI improves angiographic but not imaging or clinical outcomes compared with immediate stenting. The potential lower risk for myocardial injury by deferred stenting in primary PCI patients with STEMI and high thrombus burden requires a confirmation in adequately sized randomized trials.

Protein kinases are involved in the cardioprotective effects activated by platelet glycoprotein IIb/IIIa inhibitor tirofiban at reperfusion in rats in vivo

The thrombolytic effect of platelet glycoprotein IIb/IIIa inhibitors (GP IIb/IIIa inhibitors) in myocardial infarction has been well established. Nevertheless, data on the mechanism of the cardioprotective effect of GP IIb/IIIa inhibitors in ischemic-reperfusion injury (IR) are lacking. Sprague-Dawley rats received 120 min of coronary ischemia and 180 min of reperfusion. A GP IIb/IIIa inhibitor was given via continuous intravenous infusion at a rate of 2 μg/kg/min 30 min prior to reperfusion with/without inhibitors of PKCε (chelerythrine), PI3 kinase and Akt (wortmannin), p38 MAPK (SB203582), p42/44 MAPK (PD98059) and ERK1/2 (u0126) 15 min prior to the GP IIb/IIIa inhibitor. Protein isolation and analysis were performed by Western blot analysis. The cardioprotective effects were measured as the ratio of myocardial necrotic area to the area at risk (AAR) and the apoptotic index (AI) calculated as the percentage of myocytes positive for terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling of all myocytes stained by 4', 6-diamidino-2-phenylindole. The GP IIb/IIIa inhibitor reduced the ratio of myocardial necrotic area to AAR and AI, and also exerted an immediate cardioprotective effect by activating multiple signaling pathways including phosphorylation and activation of PKCε, PI3 kinase, Akt, p38 MAPK, p42/44 MAPK and ERK1/2. However, there were no significant increases in the phosphorylation of Raf and MEK1/2. We concluded that the GP IIb/IIIa inhibitor reduced the extent of cardiac IR and significantly ameliorate the apoptosis of myocytes in the rats. In addition, the cardioprotective effect was mediated through the activation of multiple signal transduction pathways.