Mesenchymal stromal cells for improvement of cardiac function following acute myocardial infarction: a matter of timing.

Acute myocardial infarction (AMI) is the leading cause of cardiovascular death and remains the most common cause of heart failure. Reopening of the occluded artery, i.e., reperfusion, is the only way to save the myocardium. However, the expected benefits of reducing infarct size are disappointing due to the reperfusion paradox, which also induces specific cell death. These ischemia-reperfusion (I/R) lesions can account for up to 50% of final infarct size, a major determinant for both mortality and the risk of heart failure (morbidity). In this review, we provide a detailed description of the cell death and inflammation mechanisms as features of I/R injury and cardioprotective strategies such as ischemic postconditioning as well as their underlying mechanisms. Due to their biological properties, the use of mesenchymal stromal/stem cells (MSCs) has been considered a potential therapeutic approach in AMI. Despite promising results and evidence of safety in preclinical studies using MSCs, the effects reported in clinical trials are not conclusive and even inconsistent. These discrepancies were attributed to many parameters such as donor age, in vitro culture, and storage time as well as injection time window after AMI, which alter MSC therapeutic properties. In the context of AMI, future directions will be to generate MSCs with enhanced properties to limit cell death in myocardial tissue and thereby reduce infarct size and improve the healing phase to increase postinfarct myocardial performance.

FFR-Guided Complete or Culprit-Only PCI in Patients with Myocardial Infarction.

BACKGROUND: The benefit of fractional flow reserve (FFR)-guided complete revascularization in patients with ST-segment elevation myocardial infarction (STEMI) and multivessel coronary artery disease remains unclear. METHODS: In this multinational, registry-based, randomized trial, we assigned patients with STEMI or very-high-risk non-STEMI (NSTEMI) and multivessel disease who were undergoing primary percutaneous coronary intervention (PCI) of the culprit lesion to receive either FFR-guided complete revascularization of nonculprit lesions or no further revascularization. The primary outcome was a composite of death from any cause, myocardial infarction, or unplanned revascularization. The two key secondary outcomes were a composite of death from any cause or myocardial infarction and unplanned revascularization. RESULTS: A total of 1542 patients underwent randomization, with 764 assigned to receive FFR-guided complete revascularization and 778 assigned to receive culprit-lesion-only PCI. At a median follow-up of 4.8 years (interquartile range, 4.3 to 5.2), a primary-outcome event had occurred in 145 patients (19.0%) in the complete-revascularization group and in 159 patients (20.4%) in the culprit-lesion-only group (hazard ratio, 0.93; 95% confidence interval [CI], 0.74 to 1.17; P = 0.53). With respect to the secondary outcomes, no apparent between-group differences were observed in the composite of death from any cause or myocardial infarction (hazard ratio, 1.12; 95% CI, 0.87 to 1.44) or unplanned revascularization (hazard ratio, 0.76; 95% CI, 0.56 to 1.04). There were no apparent between-group differences in safety outcomes. CONCLUSIONS: Among patients with STEMI or very-high-risk NSTEMI and multivessel coronary artery disease, FFR-guided complete revascularization was not shown to result in a lower risk of a composite of death from any cause, myocardial infarction, or unplanned revascularization than culprit-lesion-only PCI at 4.8 years. (Funded by the Swedish Research Council and others; FULL REVASC ClinicalTrials.gov number, NCT02862119.).

Beta-Blockers after Myocardial Infarction and Preserved Ejection Fraction.

BACKGROUND: Most trials that have shown a benefit of beta-blocker treatment after myocardial infarction included patients with large myocardial infarctions and were conducted in an era before modern biomarker-based diagnosis of myocardial infarction and treatment with percutaneous coronary intervention, antithrombotic agents, high-intensity statins, and renin-angiotensin-aldosterone system antagonists. METHODS: In a parallel-group, open-label trial performed at 45 centers in Sweden, Estonia, and New Zealand, we randomly assigned patients with an acute myocardial infarction who had undergone coronary angiography and had a left ventricular ejection fraction of at least 50% to receive either long-term treatment with a beta-blocker (metoprolol or bisoprolol) or no beta-blocker treatment. The primary end point was a composite of death from any cause or new myocardial infarction. RESULTS: From September 2017 through May 2023, a total of 5020 patients were enrolled (95.4% of whom were from Sweden). The median follow-up was 3.5 years (interquartile range, 2.2 to 4.7). A primary end-point event occurred in 199 of 2508 patients (7.9%) in the beta-blocker group and in 208 of 2512 patients (8.3%) in the no-beta-blocker group (hazard ratio, 0.96; 95% confidence interval, 0.79 to 1.16; P = 0.64). Beta-blocker treatment did not appear to lead to a lower cumulative incidence of the secondary end points (death from any cause, 3.9% in the beta-blocker group and 4.1% in the no-beta-blocker group; death from cardiovascular causes, 1.5% and 1.3%, respectively; myocardial infarction, 4.5% and 4.7%; hospitalization for atrial fibrillation, 1.1% and 1.4%; and hospitalization for heart failure, 0.8% and 0.9%). With regard to safety end points, hospitalization for bradycardia, second- or third-degree atrioventricular block, hypotension, syncope, or implantation of a pacemaker occurred in 3.4% of the patients in the beta-blocker group and in 3.2% of those in the no-beta-blocker group; hospitalization for asthma or chronic obstructive pulmonary disease in 0.6% and 0.6%, respectively; and hospitalization for stroke in 1.4% and 1.8%. CONCLUSIONS: Among patients with acute myocardial infarction who underwent early coronary angiography and had a preserved left ventricular ejection fraction (≥50%), long-term beta-blocker treatment did not lead to a lower risk of the composite primary end point of death from any cause or new myocardial infarction than no beta-blocker use. (Funded by the Swedish Research Council and others; REDUCE-AMI ClinicalTrials.gov number, NCT03278509.).

Restrictive or Liberal Transfusion Strategy in Myocardial Infarction and Anemia.

BACKGROUND: A strategy of administering a transfusion only when the hemoglobin level falls below 7 or 8 g per deciliter has been widely adopted. However, patients with acute myocardial infarction may benefit from a higher hemoglobin level. METHODS: In this phase 3, interventional trial, we randomly assigned patients with myocardial infarction and a hemoglobin level of less than 10 g per deciliter to a restrictive transfusion strategy (hemoglobin cutoff for transfusion, 7 or 8 g per deciliter) or a liberal transfusion strategy (hemoglobin cutoff, <10 g per deciliter). The primary outcome was a composite of myocardial infarction or death at 30 days. RESULTS: A total of 3504 patients were included in the primary analysis. The mean (±SD) number of red-cell units that were transfused was 0.7±1.6 in the restrictive-strategy group and 2.5±2.3 in the liberal-strategy group. The mean hemoglobin level was 1.3 to 1.6 g per deciliter lower in the restrictive-strategy group than in the liberal-strategy group on days 1 to 3 after randomization. A primary-outcome event occurred in 295 of 1749 patients (16.9%) in the restrictive-strategy group and in 255 of 1755 patients (14.5%) in the liberal-strategy group (risk ratio modeled with multiple imputation for incomplete follow-up, 1.15; 95% confidence interval [CI], 0.99 to 1.34; P = 0.07). Death occurred in 9.9% of the patients with the restrictive strategy and in 8.3% of the patients with the liberal strategy (risk ratio, 1.19; 95% CI, 0.96 to 1.47); myocardial infarction occurred in 8.5% and 7.2% of the patients, respectively (risk ratio, 1.19; 95% CI, 0.94 to 1.49). CONCLUSIONS: In patients with acute myocardial infarction and anemia, a liberal transfusion strategy did not significantly reduce the risk of recurrent myocardial infarction or death at 30 days. However, potential harms of a restrictive transfusion strategy cannot be excluded. (Funded by the National Heart, Lung, and Blood Institute and others; MINT ClinicalTrials.gov number, NCT02981407.).

Extracorporeal Life Support in Infarct-Related Cardiogenic Shock.

BACKGROUND: Extracorporeal life support (ECLS) is increasingly used in the treatment of infarct-related cardiogenic shock despite a lack of evidence regarding its effect on mortality. METHODS: In this multicenter trial, patients with acute myocardial infarction complicated by cardiogenic shock for whom early revascularization was planned were randomly assigned to receive early ECLS plus usual medical treatment (ECLS group) or usual medical treatment alone (control group). The primary outcome was death from any cause at 30 days. Safety outcomes included bleeding, stroke, and peripheral vascular complications warranting interventional or surgical therapy. RESULTS: A total of 420 patients underwent randomization, and 417 patients were included in final analyses. At 30 days, death from any cause had occurred in 100 of 209 patients (47.8%) in the ECLS group and in 102 of 208 patients (49.0%) in the control group (relative risk, 0.98; 95% confidence interval [CI], 0.80 to 1.19; P = 0.81). The median duration of mechanical ventilation was 7 days (interquartile range, 4 to 12) in the ECLS group and 5 days (interquartile range, 3 to 9) in the control group (median difference, 1 day; 95% CI, 0 to 2). The safety outcome consisting of moderate or severe bleeding occurred in 23.4% of the patients in the ECLS group and in 9.6% of those in the control group (relative risk, 2.44; 95% CI, 1.50 to 3.95); peripheral vascular complications warranting intervention occurred in 11.0% and 3.8%, respectively (relative risk, 2.86; 95% CI, 1.31 to 6.25). CONCLUSIONS: In patients with acute myocardial infarction complicated by cardiogenic shock with planned early revascularization, the risk of death from any cause at the 30-day follow-up was not lower among the patients who received ECLS therapy than among those who received medical therapy alone. (Funded by the Else Kröner Fresenius Foundation and others; ECLS-SHOCK ClinicalTrials.gov number, NCT03637205.).

Complete or Culprit-Only PCI in Older Patients with Myocardial Infarction.

BACKGROUND: The benefit of complete revascularization in older patients (≥75 years of age) with myocardial infarction and multivessel disease remains unclear. METHODS: In this multicenter, randomized trial, we assigned older patients with myocardial infarction and multivessel disease who were undergoing percutaneous coronary intervention (PCI) of the culprit lesion to receive either physiology-guided complete revascularization of nonculprit lesions or to receive no further revascularization. Functionally significant nonculprit lesions were identified either by pressure wire or angiography. The primary outcome was a composite of death, myocardial infarction, stroke, or any revascularization at 1 year. The key secondary outcome was a composite of cardiovascular death or myocardial infarction. Safety was assessed as a composite of contrast-associated acute kidney injury, stroke, or bleeding. RESULTS: A total of 1445 patients underwent randomization (720 to receive complete revascularization and 725 to receive culprit-only revascularization). The median age of the patients was 80 years (interquartile range, 77 to 84); 528 patients (36.5%) were women, and 509 (35.2%) were admitted for ST-segment elevation myocardial infarction. A primary-outcome event occurred in 113 patients (15.7%) in the complete-revascularization group and in 152 patients (21.0%) in the culprit-only group (hazard ratio, 0.73; 95% confidence interval [CI], 0.57 to 0.93; P = 0.01). Cardiovascular death or myocardial infarction occurred in 64 patients (8.9%) in the complete-revascularization group and in 98 patients (13.5%) in the culprit-only group (hazard ratio, 0.64; 95% CI, 0.47 to 0.88). The safety outcome did not appear to differ between the groups (22.5% vs. 20.4%; P = 0.37). CONCLUSIONS: Among patients who were 75 years of age or older with myocardial infarction and multivessel disease, those who underwent physiology-guided complete revascularization had a lower risk of a composite of death, myocardial infarction, stroke, or ischemia-driven revascularization at 1 year than those who received culprit-lesion-only PCI. (Funded by Consorzio Futuro in Ricerca and others; FIRE ClinicalTrials.gov number, NCT03772743.).

Advanced Cardiac Patches for the Treatment of Myocardial Infarction.

Myocardial infarction is a cardiovascular disease characterized by a high incidence rate and mortality. It leads to various cardiac pathophysiological changes, including ischemia/reperfusion injury, inflammation, fibrosis, and ventricular remodeling, which ultimately result in heart failure and pose a significant threat to global health. Although clinical reperfusion therapies and conventional pharmacological interventions improve emergency survival rates and short-term prognoses, they are still limited in providing long-lasting improvements in cardiac function or reversing pathological progression. Recently, cardiac patches have gained considerable attention as a promising therapy for myocardial infarction. These patches consist of scaffolds or loaded therapeutic agents that provide mechanical reinforcement, synchronous electrical conduction, and localized delivery within the infarct zone to promote cardiac restoration. This review elucidates the pathophysiological progression from myocardial infarction to heart failure, highlighting therapeutic targets and various cardiac patches. The review considers the primary scaffold materials, including synthetic, natural, and conductive materials, and the prevalent fabrication techniques and optimal properties of the patch, as well as advanced delivery strategies. Last, the current limitations and prospects of cardiac patch research are considered, with the goal of shedding light on innovative products poised for clinical application.

Half-Life and Clearance of Cardiac Troponin I and Troponin T in Humans.

BACKGROUND: Cardiac troponin (cTn) is key in diagnosing myocardial infarction (MI). After MI, the clinically observed half-life of cTn has been reported to be 7 to 20 hours, but this estimate reflects the combined elimination and simultaneous release of cTn from cardiomyocytes. More precise timing of myocardial injuries necessitates separation of these 2 components. We used a novel method for determination of isolated cTn elimination kinetics in humans. METHODS: Patients with MI were included within 24 hours after revascularization and underwent plasmapheresis to obtain plasma with a high cTn concentration. After at least 3 weeks, patients returned for an autologous plasma retransfusion followed by blood sampling for 8 hours. cTn was measured with 5 different high-sensitivity cTn assays. RESULTS: Of 25 included patients, 20 participants (mean age, 64.5 years; SD, 8.2 years; 4 women [20%]) received a retransfusion after a median of 5.8 weeks (interquartile range, 5.0-6.9 weeks) after MI. After retransfusion of a median of 620 mL (range, 180-679 mL) autologous plasma, the concentration of cTn in participants' blood increased 4 to 445 times above the upper reference level of the 5 high-sensitivity cTn assays. The median elimination half-life ranged from 134.1 minutes (95% CI, 117.8-168.0) for the Elecsys high-sensitivity cTnT assay to 239.7 minutes (95% CI, 153.7-295.1) for the Vitros high-sensitivity cTnI assay. The median clearance of cTnI ranged from 40.3 mL/min (95% CI, 32.0-44.9) to 52.7 mL/min (95% CI, 42.2-57.8). The clearance of cTnT was 77.0 mL/min (95% CI, 45.2-95.0). CONCLUSIONS: This novel method showed that the elimination half-life of cTnI and cTnT was 5 to 16 hours shorter than previously reported. This indicates a considerably longer duration of cardiomyocyte cTn release after MI than previously thought. Improved knowledge of timing of myocardial injury may call for changes in the management of MI and other disorders with myocardial injury.

Regeneration of Nonhuman Primate Hearts With Human Induced Pluripotent Stem Cell-Derived Cardiac Spheroids.

BACKGROUND: The clinical application of human induced pluripotent stem cell-derived cardiomyocytes (CMs) for cardiac repair commenced with the epicardial delivery of engineered cardiac tissue; however, the feasibility of the direct delivery of human induced pluripotent stem cell-derived CMs into the cardiac muscle layer, which has reportedly induced electrical integration, is unclear because of concerns about poor engraftment of CMs and posttransplant arrhythmias. Thus, in this study, we prepared purified human induced pluripotent stem cell-derived cardiac spheroids (hiPSC-CSs) and investigated whether their direct injection could regenerate infarcted nonhuman primate hearts. METHODS: We performed 2 separate experiments to explore the appropriate number of human induced pluripotent stem cell-derived CMs. In the first experiment, 10 cynomolgus monkeys were subjected to myocardial infarction 2 weeks before transplantation and were designated as recipients of hiPSC-CSs containing 2×107 CMs or the vehicle. The animals were euthanized 12 weeks after transplantation for histological analysis, and cardiac function and arrhythmia were monitored during the observational period. In the second study, we repeated the equivalent transplantation study using more CMs (6×107 CMs). RESULTS: Recipients of hiPSC-CSs containing 2×107 CMs showed limited CM grafts and transient increases in fractional shortening compared with those of the vehicle (fractional shortening at 4 weeks after transplantation [mean ± SD]: 26.2±2.1%; 19.3±1.8%; P<0.05), with a low incidence of posttransplant arrhythmia. Transplantation of increased dose of CMs resulted in significantly greater engraftment and long-term contractile benefits (fractional shortening at 12 weeks after transplantation: 22.5±1.0%; 16.6±1.1%; P<0.01, left ventricular ejection fraction at 12 weeks after transplantation: 49.0±1.4%; 36.3±2.9%; P<0.01). The incidence of posttransplant arrhythmia slightly increased in recipients of hiPSC-CSs containing 6×107 CMs. CONCLUSIONS: We demonstrated that direct injection of hiPSC-CSs restores the contractile functions of injured primate hearts with an acceptable risk of posttransplant arrhythmia. Although the mechanism for the functional benefits is not fully elucidated, these findings provide a strong rationale for conducting clinical trials using the equivalent CM products.

ABCG2-Expressing Clonal Repopulating Endothelial Cells Serve to Form and Maintain Blood Vessels.

BACKGROUND: Most organs are maintained lifelong by resident stem/progenitor cells. During development and regeneration, lineage-specific stem/progenitor cells can contribute to the growth or maintenance of different organs, whereas fully differentiated mature cells have less regenerative potential. However, it is unclear whether vascular endothelial cells (ECs) are also replenished by stem/progenitor cells with EC-repopulating potential residing in blood vessels. It has been reported recently that some EC populations possess higher clonal proliferative potential and vessel-forming capacity compared with mature ECs. Nevertheless, a marker to identify vascular clonal repopulating ECs (CRECs) in murine and human individuals is lacking, and, hence, the mechanism for the proliferative, self-renewal, and vessel-forming potential of CRECs is elusive. METHODS: We analyzed colony-forming, self-renewal, and vessel-forming potential of ABCG2 (ATP binding cassette subfamily G member 2)-expressing ECs in human umbilical vessels. To study the contribution of Abcg2-expressing ECs to vessel development and regeneration, we developed Abcg2CreErt2;ROSA TdTomato mice and performed lineage tracing during mouse development and during tissue regeneration after myocardial infarction injury. RNA sequencing and chromatin methylation chromatin immunoprecipitation followed by sequencing were conducted to study the gene regulation in Abcg2-expressing ECs. RESULTS: In human and mouse vessels, ECs with higher ABCG2 expression (ABCECs) possess higher clonal proliferative potential and in vivo vessel-forming potential compared with mature ECs. These cells could clonally contribute to vessel formation in primary and secondary recipients after transplantation. These features of ABCECs meet the criteria of CRECs. Results from lineage tracing experiments confirm that Abcg2-expressing CRECs (AbcCRECs) contribute to arteries, veins, and capillaries in cardiac tissue development and vascular tissue regeneration after myocardial infarction. Transcriptome and epigenetic analyses reveal that a gene expression signature involved in angiogenesis and vessel development is enriched in AbcCRECs. In addition, various angiogenic genes, such as Notch2 and Hey2, are bivalently modified by trimethylation at the 4th and 27th lysine residue of histone H3 (H3K4me3 and H3K27me3) in AbcCRECs. CONCLUSIONS: These results are the first to establish that a single prospective marker identifies CRECs in mice and human individuals, which holds promise to provide new cell therapies for repair of damaged vessels in patients with endothelial dysfunction.

Safety and Efficacy of Ticagrelor Monotherapy in Patients With Acute Coronary Syndromes Undergoing Percutaneous Coronary Intervention: An Individual Patient Data Meta-Analysis of TWILIGHT and TICO Randomized Trials.

BACKGROUND: Dual antiplatelet therapy with a potent P2Y12 inhibitor coupled with aspirin for 1 year is the recommended treatment for patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI). As an alternative, monotherapy with a P2Y12 inhibitor after a short period of dual antiplatelet therapy has emerged as a bleeding reduction strategy. METHODS: We pooled individual patient data from randomized trials that included patients with ACS undergoing PCI treated with an initial 3-month course of dual antiplatelet therapy followed by ticagrelor monotherapy versus continued ticagrelor plus aspirin. Patients sustaining a major ischemic or bleeding event in the first 3 months after PCI were excluded from analysis. The primary outcome was Bleeding Academic Research Consortium type 3 or 5 bleeding occurring between 3 and 12 months after index PCI. The key secondary end point was the composite of death, myocardial infarction, or stroke. Hazard ratios and 95% CIs were generated using Cox regression with a one-stage approach in the intention-to-treat population. RESULTS: The pooled cohort (n=7529) had a mean age of 62.8 years, 23.2% were female, and 55% presented with biomarker-positive ACS. Between 3 and 12 months, ticagrelor monotherapy significantly reduced Bleeding Academic Research Consortium 3 or 5 bleeding compared with ticagrelor plus aspirin (0.8% versus 2.1%; hazard ratio, 0.37 [95% CI, 0.24-0.56]; P<0.001). Rates of all-cause death, myocardial infarction, or stroke were not significantly different between groups (2.4% versus 2.7%; hazard ratio, 0.91 [95% CI, 0.68-1.21]; P=0.515). Findings were unchanged among patients presenting with biomarker-positive ACS. CONCLUSIONS: Among patients with ACS undergoing PCI who have completed a 3-month course of dual antiplatelet therapy, discontinuation of aspirin followed by ticagrelor monotherapy significantly reduced major bleeding without incremental ischemic risk compared with ticagrelor plus aspirin. REGISTRATION: URL: https://www.crd.york.ac.uk/prospero; Unique identifier: CRD42023449646.

Inhalable Stem Cell Exosomes Promote Heart Repair After Myocardial Infarction.

BACKGROUND: Exosome therapy shows potential for cardiac repair after injury. However, intrinsic challenges such as short half-life and lack of clear targets hinder the clinical feasibility. Here, we report a noninvasive and repeatable method for exosome delivery through inhalation after myocardial infarction (MI), which we called stem cell-derived exosome nebulization therapy (SCENT). METHODS: Stem cell-derived exosomes were characterized for size distribution and surface markers. C57BL/6 mice with MI model received exosome inhalation treatment through a nebulizer for 7 consecutive days. Echocardiographies were performed to monitor cardiac function after SCENT, and histological analysis helped with the investigation of myocardial repair. Single-cell RNA sequencing of the whole heart was performed to explore the mechanism of action by SCENT. Last, the feasibility, efficacy, and general safety of SCENT were demonstrated in a swine model of MI, facilitated by 3-dimensional cardiac magnetic resonance imaging. RESULTS: Recruitment of exosomes to the ischemic heart after SCENT was detected by ex vivo IVIS imaging and fluorescence microscopy. In a mouse model of MI, SCENT ameliorated cardiac repair by improving left ventricular function, reducing fibrotic tissue, and promoting cardiomyocyte proliferation. Mechanistic studies using single-cell RNA sequencing of mouse heart after SCENT revealed a downregulation of Cd36 in endothelial cells (ECs). In an EC-Cd36fl/- conditional knockout mouse model, the inhibition of CD36, a fatty acid transporter in ECs, led to a compensatory increase in glucose utilization in the heart and higher ATP generation, which enhanced cardiac contractility. In pigs, cardiac magnetic resonance imaging showed an enhanced ejection fraction (Δ=11.66±5.12%) and fractional shortening (Δ=5.72±2.29%) at day 28 after MI by SCENT treatment compared with controls, along with reduced infarct size and thickened ventricular wall. CONCLUSIONS: In both rodent and swine models, our data proved the feasibility, efficacy, and general safety of SCENT treatment against acute MI injury, laying the groundwork for clinical investigation. Moreover, the EC-Cd36fl/- mouse model provides the first in vivo evidence showing that conditional EC-CD36 knockout can ameliorate cardiac injury. Our study introduces a noninvasive treatment option for heart disease and identifies new potential therapeutic targets.

Myocardial Infarction with Nonobstructive Coronary Arteries.

Myocardial infarction with nonobstructive coronary arteries (MINOCA) is an important subtype of myocardial infarction (MI) that occurs in approximately 6-8% of patients with spontaneous MI who are referred for coronary angiography. MINOCA disproportionately affects women, but men are also affected. Pathogenesis is more variable than in MI with obstructive coronary artery disease (MI-CAD). Dominant mechanisms include atherosclerosis, thrombosis, and coronary artery spasm. Management of MINOCA varies based on the underlying mechanism of infarction. Therefore, systematic approaches to diagnosis are recommended. The combination of invasive coronary angiography, multivessel intracoronary imaging, provocative testing for coronary spasm, and cardiac magnetic resonance imaging provides the greatest diagnostic yield. Current clinical practice guidelines for the secondary prevention of MI are based largely on data from patients with MI-CAD. Thus, optimal medications after MINOCA are uncertain. Clinical trials focused on the treatment of patients with MINOCA are urgently needed to define optimal care.

Fractional Flow Reserve or Intravascular Ultrasonography to Guide PCI.

BACKGROUND: In patients with coronary artery disease who are being evaluated for percutaneous coronary intervention (PCI), procedures can be guided by fractional flow reserve (FFR) or intravascular ultrasonography (IVUS) for decision making regarding revascularization and stent implantation. However, the differences in clinical outcomes when only one method is used for both purposes are unclear. METHODS: We randomly assigned 1682 patients who were being evaluated for PCI for the treatment of intermediate stenosis (40 to 70% occlusion by visual estimation on coronary angiography) in a 1:1 ratio to undergo either an FFR-guided or IVUS-guided procedure. FFR or IVUS was to be used to determine whether to perform PCI and to assess PCI success. In the FFR group, PCI was to be performed if the FFR was 0.80 or less. In the IVUS group, the criteria for PCI were a minimal lumen area measuring either 3 mm2 or less or measuring 3 to 4 mm2 with a plaque burden of more than 70%. The primary outcome was a composite of death, myocardial infarction, or revascularization at 24 months after randomization. We tested the noninferiority of the FFR group as compared with the IVUS group (noninferiority margin, 2.5 percentage points). RESULTS: The frequency of PCI was 44.4% among patients in the FFR group and 65.3% among those in the IVUS group. At 24 months, a primary-outcome event had occurred in 8.1% of the patients in the FFR group and in 8.5% of those in the IVUS group (absolute difference, -0.4 percentage points; upper boundary of the one-sided 97.5% confidence interval, 2.2 percentage points; P = 0.01 for noninferiority). Patient-reported outcomes as reported on the Seattle Angina Questionnaire were similar in the two groups. CONCLUSIONS: In patients with intermediate stenosis who were being evaluated for PCI, FFR guidance was noninferior to IVUS guidance with respect to the composite primary outcome of death, myocardial infarction, or revascularization at 24 months. (Funded by Boston Scientific; FLAVOUR ClinicalTrials.gov number, NCT02673424.).

Polypill Strategy in Secondary Cardiovascular Prevention.

BACKGROUND: A polypill that includes key medications associated with improved outcomes (aspirin, angiotensin-converting-enzyme [ACE] inhibitor, and statin) has been proposed as a simple approach to the secondary prevention of cardiovascular death and complications after myocardial infarction. METHODS: In this phase 3, randomized, controlled clinical trial, we assigned patients with myocardial infarction within the previous 6 months to a polypill-based strategy or usual care. The polypill treatment consisted of aspirin (100 mg), ramipril (2.5, 5, or 10 mg), and atorvastatin (20 or 40 mg). The primary composite outcome was cardiovascular death, nonfatal type 1 myocardial infarction, nonfatal ischemic stroke, or urgent revascularization. The key secondary end point was a composite of cardiovascular death, nonfatal type 1 myocardial infarction, or nonfatal ischemic stroke. RESULTS: A total of 2499 patients underwent randomization and were followed for a median of 36 months. A primary-outcome event occurred in 118 of 1237 patients (9.5%) in the polypill group and in 156 of 1229 (12.7%) in the usual-care group (hazard ratio, 0.76; 95% confidence interval [CI], 0.60 to 0.96; P = 0.02). A key secondary-outcome event occurred in 101 patients (8.2%) in the polypill group and in 144 (11.7%) in the usual-care group (hazard ratio, 0.70; 95% CI, 0.54 to 0.90; P = 0.005). The results were consistent across prespecified subgroups. Medication adherence as reported by the patients was higher in the polypill group than in the usual-care group. Adverse events were similar between groups. CONCLUSIONS: Treatment with a polypill containing aspirin, ramipril, and atorvastatin within 6 months after myocardial infarction resulted in a significantly lower risk of major adverse cardiovascular events than usual care. (Funded by the European Union Horizon 2020; SECURE ClinicalTrials.gov number, NCT02596126; EudraCT number, 2015-002868-17.).

Uterine Immunoprivileged Cells Restore Cardiac Function of Male Recipients After Myocardial Infarction.

It has been documented that the uterus plays a key cardio-protective role in pre-menopausal women, which is supported by uterine cell therapy, to preserve cardiac functioning post-myocardial infarction, being effective among females. However, whether such therapies would also be beneficial among males is still largely unknown. In this study, we aimed to fill in this gap in knowledge by examining the effects of transplanted uterine cells on infarcted male hearts. We identified, based on major histocompatibility complex class I (MHC-I) expression levels, 3 uterine reparative cell populations: MHC-I(neg), MHC-I(mix), and MHC-I(pos). In vitro, MHC-I(neg) cells showed higher levels of pro-angiogenic, pro-survival, and anti-inflammatory factors, compared to MHC-I(mix) and MHC-I(pos). Furthermore, when cocultured with allogeneic mixed leukocytes, MHC-I(neg) had lower cytotoxicity and leukocyte proliferation. In particular, CD8+ cytotoxic T cells significantly decreased, while CD4+CD25+ Tregs and CD4-CD8- double-negative T cells significantly increased when cocultured with MHC-I(neg), compared to MHC-I(mix) and MHC-I(pos) cocultures. In vivo, MHC-I(neg) as well as MHC-I(mix) were found under both syngeneic and allogeneic transplantation in infarcted male hearts, to significantly improve cardiac function and reduce the scar size, via promoting angiogenesis in the infarcted area. All of these findings thus support the view that males could also benefit from the cardio-protective effects observed among females, via cell therapy approaches involving the transplantation of immuno-privileged uterine reparative cells in infarcted hearts.

Surface engineering enhances the therapeutic potential of systemically delivered extracellular vesicles following acute myocardial infarction.

The objective of the study was to assess the therapeutic efficacy of targeting remote zone cardiomyocytes with cardiosphere-derived cell (CDC) extracellular vesicles (EVs) delivered via intramyocardial and intravenous routes following acute myocardial infarction (MI). Cardiomyocyte (CM) cell death plays a significant role in left ventricular (LV) remodeling and cardiac dysfunction following MI. While EVs secreted by CDCs have shown efficacy in promoting cardiac repair in preclinical models of MI, their translational potential is limited by their biodistribution and requirement for intramyocardial delivery. We hypothesized that engineering the surface of EVs to target cardiomyocytes would enhance their therapeutic efficacy following systemic delivery in a model of acute MI. CDC-derived EVs were engineered to express a CM-specific binding peptide (CMP) on their surface and characterized for size, morphology, and protein expression. Mice with acute MI underwent both intramyocardial and intravenous delivery of EVs, CMP-EVs and placebo in a double-blind study. LVEF was assessed by echo at 2- and 28-days post-MI and tissue samples processed for assessment of EV biodistribution and histological endpoints. CMP-EVs demonstrated superior cardiac targeting and retention when compared with unmodified EVs 24 h post-MI. Mice treated with IV delivered CMP-EVs demonstrated a significant improvement in LVEF and a significant reduction in remote zone cardiomyocyte apoptosis when compared with IV delivered non-targeted EVs at 28-day post-MI. Systemic administration of CMP-EVs improved cardiac function and reduced remote zone cardiomyocyte apoptosis compared with IV-administered unmodified EVs, demonstrating a strategy to optimize therapeutic EV delivery post-MI.

MicroRNA therapy stimulates uncontrolled cardiac repair after myocardial infarction in pigs.

Prompt coronary catheterization and revascularization have markedly improved the outcomes of myocardial infarction, but have also resulted in a growing number of surviving patients with permanent structural damage of the heart, which frequently leads to heart failure. There is an unmet clinical need for treatments for this condition1, particularly given the inability of cardiomyocytes to replicate and thereby regenerate the lost contractile tissue2. Here we show that expression of human microRNA-199a in infarcted pig hearts can stimulate cardiac repair. One month after myocardial infarction and delivery of this microRNA through an adeno-associated viral vector, treated animals showed marked improvements in both global and regional contractility, increased muscle mass and reduced scar size. These functional and morphological findings correlated with cardiomyocyte de-differentiation and proliferation. However, subsequent persistent and uncontrolled expression of the microRNA resulted in sudden arrhythmic death of most of the treated pigs. Such events were concurrent with myocardial infiltration of proliferating cells displaying a poorly differentiated myoblastic phenotype. These results show that achieving cardiac repair through the stimulation of endogenous cardiomyocyte proliferation is attainable in large mammals, however dosage of this therapy needs to be tightly controlled.

In acute MI and anemia, restrictive vs. liberal transfusion did not differ for a composite of recurrent MI or death at 30 d.

SOURCE CITATION: Carson JL, Brooks MM, Hebert PC, et al; MINT Investigators. Restrictive or liberal transfusion strategy in myocardial infarction and anemia. N Engl J Med. 2023;389:2446-2456. 37952133.

Trends and Disparities in Ambulatory Follow-Up After Cardiovascular Hospitalizations : A Retrospective Cohort Study.

BACKGROUND: Timely follow-up after cardiovascular hospitalization is recommended to monitor recovery, titrate medications, and coordinate care. OBJECTIVE: To describe trends and disparities in follow-up after acute myocardial infarction (AMI) and heart failure (HF) hospitalizations. DESIGN: Retrospective cohort study. SETTING: Medicare. PARTICIPANTS: Medicare fee-for-service beneficiaries hospitalized between 2010 and 2019. MEASUREMENTS: Receipt of a cardiology visit within 30 days of discharge. Multivariable logistic regression models were used to estimate changes over time overall and across 5 sociodemographic characteristics on the basis of known disparities in cardiovascular outcomes. RESULTS: The cohort included 1 678 088 AMI and 4 245 665 HF hospitalizations. Between 2010 and 2019, the rate of cardiology follow-up increased from 48.3% to 61.4% for AMI hospitalizations and from 35.2% to 48.3% for HF hospitalizations. For both conditions, follow-up rates increased for all subgroups, yet disparities worsened for Hispanic patients with AMI and patients with HF who were Asian, Black, Hispanic, Medicaid dual eligible, and residents of counties with higher levels of social deprivation. By 2019, the largest disparities were between Black and White patients (AMI, 51.9% vs. 59.8%, difference, 7.9 percentage points [pp] [95% CI, 6.8 to 9.0 pp]; HF, 39.8% vs. 48.7%, difference, 8.9 pp [CI, 8.2 to 9.7 pp]) and Medicaid dual-eligible and non-dual-eligible patients (AMI, 52.8% vs. 60.4%, difference, 7.6 pp [CI, 6.9 to 8.4 pp]; HF, 39.7% vs. 49.4%, difference, 9.6 pp [CI, 9.2 to 10.1 pp]). Differences between hospitals explained 7.3 pp [CI, 6.7 to 7.9 pp] of the variation in follow-up for AMI and 7.7 pp [CI, 7.2 to 8.1 pp]) for HF. LIMITATION: Generalizability to other payers. CONCLUSION: Equity-informed policy and health system strategies are needed to further reduce gaps in follow-up care for patients with AMI and patients with HF. PRIMARY FUNDING SOURCE: National Institute on Aging.