ST-segment resolution and late (6-month) left ventricular remodeling after acute myocardial infarction

A review of therapeutic approaches for post-infarction left ventricular remodeling

Left ventricular remodeling is an adaptive process initially developed in response to acute myocardial infarction (AMI), but it ends up with negative adverse outcomes such as infarcted wall thinning, ventricular dilation, and cardiac dysfunction. A prolonged excessive inflammatory reaction to cardiomyocytes death and necrosis plays the crucial role in the pathophysiological mechanisms. The pharmacological treatment includes nitroglycerine, β-blockers, ACEi/ARBs, SGLT2i, mineralocorticoid receptor antagonists, and some miscellaneous aspects. Stem cells therapy, CD34+ cells transplantation and gene therapy constitute the promissing therapeutic approaches for post AMI cardiac remodeling, thereby enhancing angiogenesis, cardiomyocytes differenciation and left ventricular function on top of inhibiting apoptosis, inflammation, and collagen deposition. All these lead to reduce infarct size, scar formation and myocardial fibrosis.

Severe Impairment of Left Ventricular Regional Strain in STEMI Patients Is Associated with Post-Infarct Remodeling

Background: Measures of global left ventricular (LV) systolic function have limitations for the prediction of post-infarct LV remodeling (LVR). Therefore, we tested the association between a new measure of regional LV systolic function—the percentage of severely altered strain (%SAS)- and LVR after acute ST-elevation myocardial infarction (STEMI). As a secondary objective, we also evaluated the association between %SAS and clinical events during follow-up. Methods: Of 177 patients undergoing echocardiography within 24 h from primary percutaneous coronary angioplasty, 172 were studied for 3 months, 167 for 12 months, and 10 died. The %SAS was calculated by dividing the number of LV myocardial segments with ≥−5% peak systolic longitudinal strain by the total number of segments. LVR was defined as the increase in end-diastolic volume >20% at its first occurrence compared to baseline. Results: LVR percentage was 10.2% and 15.8% at 3 and 12 months, respectively. Based on univariable analysis, a number of clinical, laboratory, electrocardiographic and echocardiographic variables were associated with LVR. Based on multivariable analysis, %SAS and TnI peak remained associated with LVR (for %SAS 5% increase, OR 1.226, 95% CI 1.098−1.369, p < 0.0005; for TnI peak, OR 1.025, 95% CI 1.004−1.047, p = 0.022). %SAS and LVR were also associated with occurrence of clinical events at a median follow-up of 43 months (HR 1.02, 95% CI 1.0−1.04, p = 0.0165). Conclusions: In patients treated for acute STEMI, acute %SAS is associated with post-infarct LVR. Therefore, we suggest performing such evaluations on a routine basis to identify, as early as possible, STEMI patients at higher risk.

Effects of Ticagrelor and Clopidogrel on Coronary Microcirculation in Patients with Acute Myocardial Infarction

Introduction

Clopidogrel has been demonstrated to be effective in improving coronary microcirculation (CM) among patients with ST-elevation myocardial infarction (STEMI) treated with fibrinolytics. Ticagrelor is a more potent adenosine diphosphate (ADP) receptor blocker proven to be superior to clopidogrel among patients with acute coronary syndromes. The present study aimed to compare the effects of ticagrelor and clopidogrel on CM in patients with STEMI treated with fibrinolytics.

Methods

The present study prospectively included 48 patients participating in the TREAT trial, which randomly assigned patients with STEMI undergoing fibrinolysis to ticagrelor versus clopidogrel. The primary endpoint of this study was the evaluation of the CM using the global myocardial perfusion score index (global MPSI) obtained by myocardial contrast echocardiography (MCE). Platelet aggregation to ADP was evaluated by Multiplate® and expressed as area under the curve (AUC).

Results

The global MPSI demonstrated no differences between the groups [mean 1.4 (1.2–1.5) in the ticagrelor group and 1.2 (1.2–1.5) in the clopidogrel group (p = 0.41)]. Platelet aggregability was lower in the ticagrelor group (18.1 ± 9.7 AUC), compared to the clopidogrel group (26.1 ± 12.5 AUC, p = 0.01).

Conclusion

We found no improvement in coronary microcirculation with ticagrelor compared to clopidogrel among patients with STEMI treated with fibrinolytics, despite the fact that platelet aggregation to ADP was lower with ticagrelor.

Clinical Trials Registration

NCT03104062.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-022-02061-0.

Sonothrombolysis in ST-Segment Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention

BACKGROUND

Preclinical studies have demonstrated that high mechanical index (MI) impulses from a diagnostic ultrasound transducer during an intravenous microbubble infusion (sonothrombolysis) can restore epicardial and microvascular flow in acute ST-segment elevation myocardial infarction (STEMI).

OBJECTIVES

This study tested the clinical effectiveness of sonothrombolysis in patients with STEMI.

METHODS

Patients with their first STEMI were prospectively randomized to either diagnostic ultrasound-guided high MI impulses during an intravenous Definity (Lantheus Medical Imaging, North Billerica, Massachusetts) infusion before, and following, emergent percutaneous coronary intervention (PCI), or to a control group that received PCI only (n = 50 in each group). A reference first STEMI group (n = 203) who arrived outside the randomization window was also analyzed. Angiographic recanalization before PCI, ST-segment resolution, infarct size by magnetic resonance imaging, and systolic function (LVEF) at 6 months were compared.

RESULTS

ST-segment resolution occurred in 16 (32%) high MI PCI versus 2 (4%) PCI-only patients before PCI, and angiographic recanalization was 48% in high MI/PCI versus 20% in PCI only and 21% in the reference group (p < 0.001). Infarct size was reduced (29 ± 22 g high MI/PCI vs. 40 ± 20 g PCI only; p = 0.026). LVEF was not different between groups before treatment (44 ± 11% vs. 43 ± 10%), but increased immediately after PCI in the high MI/PCI group (p = 0.03), and remained higher at 6 months (p = 0.015). Need for implantable defibrillator (LVEF ≤30%) was reduced in the high MI/PCI group (5% vs. 18% PCI only; p = 0.045).

CONCLUSIONS

Sonothrombolysis added to PCI improves recanalization rates and reduces infarct size, resulting in sustained improvements in systolic function after STEMI. (Therapeutic Use of Ultrasound in Acute Coronary Artery Disease; NCT02410330).

Stem-cell therapy in ST-segment elevation myocardial infarction with reduced ejection fraction: A multicenter, double-blind randomized trial

BACKGROUND

Left ventricular ejection fraction (LVEF) is a major determinant of long-term prognosis after ST-segment elevation myocardial infarction (STEMI). STEMI patients with reduced LVEF have a poor prognosis, despite successful reperfusion and the use of renin-angiotensin-aldosterone inhibitors.

HYPOTHESIS

Intracoronary infusion of bone marrow-derived mononuclear cells (BMMC) may improve LVEF in STEMI patients successfully reperfused.

METHODS

The main inclusion criteria for this double-blind, randomized, multicenter study were patient age 30 to 80 years, LVEF ≤50%, successful angioplasty of infarct-related artery, and regional dysfunction in the infarct-related area analyzed before cell injection. Cardiac magnetic resonance imaging was used to assess LVEF, left ventricular volumes, and infarct size at 7 to 9 days and 6 months post-myocardial infarction.

RESULTS

One hundred and twenty-one patients were included (66 patients in the BMMC group and 55 patients in the placebo group). The primary endpoint, mean LVEF, was similar between both groups at baseline (44.63% ± 10.74% vs 42.23% ± 10.33%; P = 0.21) and at 6 months (44.74% ± 12.95 % vs 43.50 ± 12.43%; P = 0.59). The groups were also similar regarding the difference between baseline and 6 months (0.11% ± 8.5% vs 1.27% ± 8.93%; P = 0.46). Other parameters of left ventricular remodeling, such as systolic and diastolic volumes, as well as infarct size, were also similar between groups.

CONCLUSIONS

In this randomized, multicenter, double-blind trial, BMMC intracoronary infusion did not improve left ventricular remodeling or decrease infarct size.

In patients with acute myocardial infarction, the impact of hyperglycemia as a risk factor for mortality is not homogeneous across age-groups

OBJECTIVE

To assess the impact of hyperglycemia in different age-groups of patients with acute myocardial infarction (AMI).

RESEARCH DESIGN AND METHODS

A total of 2,027 patients with AMI were categorized into one of five age-groups: <50 years (n = 301), ≥50 and <60 (n = 477), ≥60 and <70 (n = 545), ≥70 and <80 (n = 495), and ≥80 years (n = 209). Hyperglycemia was defined as initial glucose ≥115 mg/dL.

RESULTS

The adjusted odds ratios for hyperglycemia predicting hospital mortality in groups 1-5 were, respectively, 7.57 (P = 0.004), 3.21 (P = 0.046), 3.50 (P = 0.003), 3.20 (P < 0.001), and 2.16 (P = 0.021). The adjusted P values for correlation between glucose level (as a continuous variable) and mortality were 0.007, <0.001, 0.043, <0.001, and 0.064. The areas under the ROC curves (AUCs) were 0.785, 0.709, 0.657, 0.648, and 0.613. The AUC in group 1 was significantly higher than those in groups 3-5.

CONCLUSIONS

The impact of hyperglycemia as a risk factor for hospital mortality in AMI is more pronounced in younger patients.

Baseline glucose and left ventricular remodeling after acute myocardial infarction

In patients with acute myocardial infarction (AMI), the mechanisms behind the increased mortality related to glucose levels (GL) are poorly understood. The main purpose of this study is to analyze the relationship between baseline glucose and left ventricular enlargement (LVE). We analyzed 52 patients with a first ST-elevation AMI <24 h of evolution. Glucose levels were obtained upon admission (median time, 3 h after the beginning of chest pain). The median GL was 123.5 mg/dl, and patients above this limit were considered hyperglycemic (n=26). Left ventricular enlargement was analyzed comparing two radionuclide ventriculographies, the first obtained within 4 days post-AMI (median, 55 h) and the second 6 months later (median, 188.5 days), taking into account the difference in the obtained end-systolic volumes. Myocardial reperfusion was evaluated comparing ST resolution between a first ECG done immediately upon hospital arrival with a second ECG performed 2 h after treatment. By univariate analysis, LVE correlated significantly with baseline hyperglycemia (P<.001), failed reperfusion by ECG criteria (P<.001), and no use of ACE inhibitors or AT1 blockers (P=.046) and aspirin (P=.046). A history of previous diabetes did not correlate significantly with LVE at 6 months. In the adjusted model, basal hyperglycemia (P<.001) and failed reperfusion (P=.001) were the only variables independently correlated with LVE. In conclusion, baseline glucose is a powerful and independent predictor of LVE after AMI, which reinforces the importance of a tight glucose control during the initial phase of the disease.

ST-segment analysis to predict infarct size and functional outcome in acute myocardial infarction treated with primary coronary intervention and adjunctive abciximab therapy

ST-segment resolution is used to classify the response to reperfusion therapy in acute myocardial infarction, but the possibility to predict outcome in individual patients is unclear, particularly in the setting of primary percutaneous coronary intervention (PCI) and abciximab therapy. We studied 213 patients who underwent successful revascularization with PCI. Maximal ST-segment elevation was measured before and 30 minutes after PCI. Patient outcome was defined on the basis of infarct size and left ventricular ejection fraction (EF) as derived from gated single-photon emission computed tomography that was acquired 1 month after infarction. Patients who had > or =50% ST resolution showed a smaller infarct (15.1 +/- 13.6% vs 19.9 +/- 15.7%, p < 0.05) but not a higher left ventricular EF (48.7 +/- 12.3% vs 45.2 +/- 11.8%) than did patients who had <50% resolution. According to cluster analysis of infarct size and left ventricular EF, 132 patients had favorable outcome (central values: infarct size 7.5%, left ventricular EF 55%) and 81 did not (central values: infarct size 30%, left ventricular EF 36%). Using receiver-operating characteristic curve analysis, the optimal ST-resolution cutoff was >60%, with 77% sensitivity and 51% specificity for predicting favorable outcome. ST-segment elevation < or =4.5 mV before PCI was 80% sensitive and 48% specific, and ST-segment elevation < or =1 mV after PCI was 74% sensitive and 60% specific for predicting favorable outcome. In conclusion, in the setting of primary PCI and abciximab therapy, ST-segment elevation resolution requires a high threshold (>60%) to effectively classify patients; the capability of ST-segment analysis to predict patient outcome is limited, with ST-segment elevation after PCI showing the best compromise between sensitivity and specificity.

Role of Sam68 as an adaptor protein in signal transduction

Sam68, the substrate of Src in mitosis, belongs to the family of RNA binding proteins. Sam68 contains consensus sequences to interact with other proteins via specific domains. Thus, Sam68 has various proline-rich sequences to interact with SH3 domain-containing proteins. Moreover, Sam68 also has a C-terminal domain rich in tyrosine residues that is a substrate for tyrosine kinases. Tyrosine phosphorylation of Sam68 promotes its interaction with SH2 containing proteins. The association of Sam68 with SH3 domain-containing proteins, and its tyrosine phosphorylation may negatively regulate its RNA binding activity. The presence of these consensus sequences to interact with different domains allows this protein to participate in signal transduction pathways triggered by tyrosine kinases. Thus, Sam68 participates in the signaling of T cell receptors, leptin and insulin receptors. In these systems Sam68 is tyrosine phosphorylated and recruited to specific signaling complexes. The participation of Sam68 in signaling suggests that it may function as an adaptor molecule, working as a dock to recruit other signaling molecules. Finally, the connection between this role of Sam68 in protein-protein interaction with RNA binding activity may connect signal transduction of tyrosine kinases with the regulation of RNA metabolism.