Invasive Evaluation of the Microvasculature in Acute Myocardial Infarction: Coronary Flow Reserve versus the Index of Microcirculatory Resistance

Pre-hospital pulse glucocorticoid therapy in patients with ST-segment elevation myocardial infarction transferred for primary percutaneous coronary intervention: a randomized controlled trial (PULSE-MI)

BACKGROUND

Inflammation in ST-segment elevation myocardial infarction (STEMI) is an important contributor to both acute myocardial ischemia and reperfusion injury after primary percutaneous coronary intervention (PCI). Methylprednisolone is a glucocorticoid with potent anti-inflammatory properties with an acute effect and is used as an effective and safe treatment of a wide range of acute diseases. The trial aims to investigate the cardioprotective effects of pulse-dose methylprednisolone administered in the pre-hospital setting in patients with STEMI transferred for primary PCI.

METHODS

This trial is a randomized, blinded, placebo-controlled prospective clinical phase II trial. Inclusion will continue until 378 patients with STEMI have been evaluated for the primary endpoint. Patients will be randomized 1:1 to a bolus of 250 mg methylprednisolone intravenous or matching placebo over a period of 5 min in the pre-hospital setting. All patients with STEMI transferred for primary PCI at Rigshospitalet, Copenhagen University Hospital, Denmark, will be screened for eligibility. The main eligibility criteria are age ≥ 18 years, acute onset of chest pain with < 12 h duration, STEMI on electrocardiogram, no known allergy to glucocorticoids or no previous coronary artery bypass grafting, previous acute myocardial infarction in assumed culprit, or a history with previous maniac/psychotic episodes. Primary outcome is final infarct size measured by late gadolinium enhancement on cardiac magnetic resonance (CMR) 3 months after STEMI. Secondary outcomes comprise key CMR efficacy parameters, clinical endpoints at 3 months, the peak of cardiac biomarkers, and safety.

DISCUSSION

We hypothesize that pulse-dose methylprednisolone administrated in the pre-hospital setting decreases inflammation and thus reduces final infarct size in patients with STEMI treated with primary PCI.

TRIAL REGISTRATION

EU-CT number: 2022-500762-10-00; Submitted May 5, 2022.

CLINICALTRIALS

gov Identifier: NCT05462730; Submitted July 7, 2022, first posted July 18, 2022.

Comparison of intracoronary versus intravenous tirofiban in acute ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention

OBJECTIVE

This study aimed to investigate the effect of intracoronary (IC) tirofiban compared to intravenously administered tirofiban in STEMI patients treated with PPCI.

METHODS

This study included 180 STEMI patients who were underwent PPCI. Patients were randomized into an IC group (n = 90) and intravenous (IV) group (n = 90). During the procedure, the both groups were administered IC or IV injections of tirofiban, respectively, followed by an IV infusion of tirofiban for 24 hours. Changes in TIMI flow grading, TMP grade 3, Sum-STR two hours after the operation, the number of thrombus aspirations during the operation, myocardial enzyme, inflammatory factors,cardiac functional parameters, MACE and bleeding were investigated.

RESULTS

Following treatment, TIMI flow grading and TMP grade 3 were improved in the IC tirofiban compared to the IV group (P = 0.022 and P = 0.014, respectively). Additionally, the Sum-STR two hours after operation, the incidence of MACEs, levels of AST, CRP, ESR, and TNI in the IC group was improved, compared with the IV group (all P < 0.05). Furthermore. Cardiac function including CO and LVEF were significantly improved in the IC group 6 months after discharge.

CONCLUSION

This study found that IC administration of tirofiban in patients with STEMI who underwent PPCI improved TIMI, TMP flow and cardiac function 6 months after discharge, and reduced CRP, ESR, and TNI. However, the incidence of bleeding between the two groups was comparable. These findings suggest that IC administration should be applied in certain acute STEMI patients.

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.

Index of microcirculatory resistance predicts long term cardiac systolic function in patients with STEMI undergoing primary PCI

Background

To evaluate the predictive value of the index of microcirculatory resistance (IMR) for long-term cardiac systolic function after primary percutaneous coronary intervention (pPCI) in patients with acute anterior wall ST-segment elevation myocardial infarction (STEMI).

Methods

A total of 53 acute anterior wall STEMI patients were included and followed up within 1-year. IMR was measured to evaluate the immediate intraoperative reperfusion. IMR > 40 U was defined as the high IMR group and ≤ 40 U was defined as the low IMR group. Left ventricular ejection fraction (LVEF) was measured by echocardiography at 24 h, 1 month, 3 months, and 1 year after PCI to analyze the correlation between IMR and cardiac systolic function. Heart failure was estimated according to classification within one year.

Results

The ratio of TMPG (TIMI myocardial perfusion grade) 3 (85.7% vs. 52%, p = 0.015) and STR (ST-segment resolution) > 70% (82.1% vs. 48%, p = 0.019) were significantly higher in the low IMR group. The LVEF in the low IMR group was significantly higher than that in the high IMR group at 3 months (43.06 ± 2.63% vs. 40.20 ± 2.67%, p < 0.001) and 1 year (44.16 ± 2.40% vs. 40.13 ± 3.48%, p < 0.001). IMR was negatively correlated with LVEF at 3 months (r = − 0.1014, p = 0.0040) and 1 year (r = − 0.1754, p < 0.0001).

Conclusions

The IMR showed significant negative correlation with the LVEF value after primary PCI. The high IMR is a strong predictor of heart failure within 1 year after anterior myocardial infarction.

Determining the Significance of Coronary Plaque Lesions: Physiological Stenosis Severity and Plaque Characteristics

The evaluation of coronary lesions has evolved in recent years. Physiologic-guided revascularization (particularly with pressure-derived fractional flow reserve (FFR)) has led to superior outcomes compared to traditional angiographic assessment. A greater importance, therefore, has been placed on the functional significance of an epicardial lesion. Despite the improvements in the limitations of angiography, insights into the relationship between hemodynamic significance and plaque morphology at the lesion level has shown that determining the implications of epicardial lesions is rather complex. Investigators have sought greater understanding by correlating ischemia quantified by FFR with plaque characteristics determined on invasive and non-invasive modalities. We review the background of the use of these diagnostic tools in coronary artery disease and discuss the implications of analyzing physiological stenosis severity and plaque characteristics concurrently.

Invasive Assessment of the Myocardial Microcirculation during Beating Heart Coronary Artery Bypass Grafting

Coronary artery bypass grafting may be associated with several cardiac complications, including ischemia, acute myocardial infarction, arrhythmias, or hemodynamic instability. Accumulating evidence suggests that well-developed coronary collateral circulation may protect against adverse effects, including myocardial ischemia. Assessment of myocardial microvascular perfusion is, therefore, of great clinical interest in beating heart surgery. In this paper, myocardial microvascular perfusion is continuously assessed on the beating heart using laser Doppler flowmetry in consecutive patients who underwent coronary artery bypass grafting procedures. No significant (p = 0.110) differences were found between the averaged perfusion signal (n = 42) at the baseline, during artery occlusion, or after reperfusion (732.4 ± 148.0 vs. 711.4 ± 144.1 vs. 737.0 ± 141.2, respectively). In contrast, significantly different (p < 0.001) mean perfusion signals (n = 12) were found (805.4 ± 200.1 vs. 577.2 ± 212.8 vs. 649.3 ± 220.8) in a subset of patients who presented with hemodynamic instability and myocardial ischemia. Additionally, a strong positive correlation between the plasma levels of high-sensitivity troponin I and perfusion decrease level after artery occlusion was found (r = 0.854, p < 0.001). This study argues that myocardial microvascular perfusion remains constant during coronary artery bypass grafting on the beating heart in advanced coronary artery disease. This phenomenon is most likely due to an extensive coronary collateral circulation.