Chronic Myocardial Infarction Research Articles

Remnant cholesterol, not LDL cholesterol, explains peripheral artery disease risk conferred by apolipoprotein B: a cohort study

Abstract Background Elevated apolipoprotein B (apoB)-containing lipoproteins (=remnants + low-density lipoproteins [LDL]) are a major risk factor for atherosclerotic cardiovascular disease, including peripheral artery disease (PAD) and myocardial infarction. We tested the hypothesis that remnants and LDL both explain part of the increased risk of PAD conferred by elevated apoB-containing lipoproteins. For comparison, we also studied risk of chronic limb-threatening ischemia and myocardial infarction. Methods ApoB, remnant cholesterol, and LDL cholesterol were measured in 93,461 individuals without statin use at baseline from the Copenhagen General Population Study (2003-2015). During up to 15 years of follow-up, 1,207 had PAD, 552 had chronic limb threatening ischemia, and 2,022 had myocardial infarction in the national Danish Patient Registry. Remnant and LDL cholesterol were calculated from a standard-lipid profile. Remnant and LDL particle counts were additionally measured with nuclear magnetic resonance spectroscopy in 25,347 of the individuals. Results were replicated in 302,167 individuals without statin use from the UK Biobank (2004-2010). Results In the Copenhagen General Population Study, multivariable adjusted hazard ratios for risk of PAD per 1 mmol/L (39 mg/dL) increment in remnant and LDL cholesterol were 1.9 (95% confidence interval: 1.5-2.4) and 1.1 (1.0-1.2), respectively; corresponding results in the UK Biobank were 1.7 (1.4-2.1) and 0.9 (0.9-1.0), respectively. In the association from elevated apoB to increased risk of PAD, remnant and LDL cholesterol explained 73% (32-100%) and 8% (0-46%), respectively; corresponding results were 63% (30-100%) and 0% (0-33%) for risk of chronic limb-threatening ischemia, and 41% (27-55%) and 54% (38-70%) for risk of myocardial infarction; results for remnant and LDL particle counts corroborated these findings. Conclusions PAD risk conferred by elevated apoB-containing lipoproteins was explained mainly by elevated remnants, while myocardial infarction risk was explained by both elevated remnants and LDL.

The incidence of atrial fibrillation in patients with interatrial shunt: is it reduced after surgical or transcatheter closure of the shunt?

Abstract Background Atrial fibrillation (AF) is a prevalent diagnosis among individuals with interatrial shunts, and the prevalence increases with age (1). Since the 1990s, interventionists have introduced transcatheter techniques, to close interatrial shunts, while surgical procedures reserved in cases of technical complexity (2). Despite the potential reduction in AF incidence post interatrial shunt closure, discernible modifications in the cardiac conduction system may persist (3). Notwithstanding, reports indicate an incidence of new-onset AF in approximately 10-25% of patients after interatrial shunt closure, with a pronounced prevalence among elderly (4). This study aims to delineate the incidence of AF subsequent to interatrial shunt, surgical och transcatheter, closure within a national cohort in Sweden. Methods The study includes all patients diagnosed with an interatrial shunt, atrial septal defect and patent foramen ovale, classified using the International Classification of Diseases, 10th edition (ICD-10), as documented in the Swedish National Patient Register, along with data sourced from the Cause of Death Register. Patients with multiple diagnoses of other congenital heart diseases are excluded, and interventions performed between 1997 and 2017 are identified using the NOMESCO surgical classification. Comorbidities such as chronic ischemic heart disease, myocardial infarction, heart failure, hypertension, and diabetes are considered, with the primary endpoint being the incidence of AF post-intervention. Results A total of 3,426 patients with interatrial shunts underwent intervention between 1997 and 2017, with a mean follow-up duration of 6.2 years. Among these, 49% (n=1,725) underwent transcatheter closure, while 41 patients underwent both transcatheter and surgical procedures. The mean age was 36 years, with 9% presenting with heart failure at baseline. Before the intervention, 14% (n=483) had AF, increasing to 22% (n=755) post-intervention. Of those developing AF post-intervention, 16% (n=119) experienced the AF event within 60 days, evenly distributed between transcatheter and surgical procedures. Over 40% of patients with post-intervention AF had an average age of 62. The incidence of AF post-intervention was 1.6 per 100 patient-years (see Figure). Stroke incidence was 3.6 per 100 patient-years and the mortality rate was 7% (n=257) during follow up (see Table). Conclusions Patients with interatrial shunts exhibit a high incidence of AF, which further escalates following closure of the interatrial shunt, not only within the first few days post-intervention, particularly among the elderly population. This can relate to high incidence of ischemic stroke.Figure

Quantification of myocardial oxygen extraction fraction on noncontrast MRI enabled by deep learning

Abstract Purpose To develop a new deep learning enabled cardiovascular magnetic resonance (CMR) approach for noncontrast quantification of myocardial oxygen extraction fraction (mOEF) and myocardial blood volume (MBV) in vivo. Materials and Methods An asymmetric-spin-echo prepared CMR sequence was created in a 3 T MRI clinical system. A UNet-based fully connected neural network was developed based on a theoretical model of CMR signals to calculate mOEF and MBV. Twenty healthy volunteers (20–30 years old, 11 females) underwent CMR scans at three short-axial slices (16 myocardial segments) on two different days. The reproducibility was assessed by the coefficient of variation (CV). Ten patients with chronic myocardial infarction were examined to evaluate the feasibility of this CMR method to detect abnormality of mOEF and MBV. Results Among the volunteers, the average global mOEF and MBV on both days was 0.58 ± 0.07 and 9.5% ± 1.5%, respectively, which agreed well with data measured by other imaging modalities. The CV of mOEF was 8.4%, 4.5%, and 2.6%, on a basis of segment, slice, and participant, respectively. No significant difference in mOEF was shown among three slices or among different myocardial segments. Female participants showed significantly higher segmental mOEF than male participants (p < 0.001). Regional mOEF decrease 40% in CMR confirmed myocardial infarction core, compared to normal myocardial regions. Conclusion The new deep learning enabled CMR approach allows noncontrast quantification of mOEF and MBV with good to excellent reproducibility. This technique could provide an objective contrast-free means to assess and serially measure hypoxia-relief effects of therapeutic interventional strategies to save viable myocardial tissues.

Impact of Multidirectional Pacing on Activation and Repolarization Parameters to Localize Ischemic Ventricular Tachycardia Circuits.

In ventricular tachycardia (VT), optimal substrate mapping strategies identifying arrhythmogenic sites are not established. This study sought to evaluate multidirectional pacing on the distribution of specific conduction and repolarization metrics to localize re-entrant VT sites in a porcine infarct model. Substrate maps were created in 13 pigs with chronic myocardial infarction using the Advisor HD Grid (Abbott) during right ventricular (RV), left ventricular, biventricular pacing (BIV), and sinus rhythm (SR). Critical VT sites of early-, mid-, and late-diastolic signals were delineated. Vulnerable sites to re-entry were defined as sites of latest activation timing within and post-QRS complex, largest activation and activation-recovery interval gradients. Distances between the 20 most vulnerable sites and diastolic VT points were measured, and identification of VT points was assessed using the area under the receiver-operating characteristic curve. A total of 34 VTs were mapped, and 48 sinus and pacing maps were obtained (10 BIV, 13 left ventricular, 13 RV, 12 SR). Late potential mapping in SR was taken as the established clinical standard for comparison. Latest activation time with BIV pacing provided the closest localization for VT isthmus (median 5.5mm; IQR: 7.15mm; P< 0.005). The gradient of activation-recovery interval using RV pacing had closest localization for VT exit and entrance (median 10.6mm; IQR: 5.0mm; P< 0.005 and 9.4mm; IQR: 8.0mm; P< 0.05). Global sensitivity and specificity analysis showed that gradient of activation-recovery interval in SR achieved the highest area under the receiver-operating characteristic curve, with similar results from the gradient of activation timing. Multidirectional pacing in combination with conduction and repolarization parameters enables better localization of VT diastolic critical sites vs SR late potentials.

Long-term transcranial ultrasound stimulation regulates neuroinflammation to ameliorate post–myocardial infarction cardiac arrhythmia and remodeling

BackgroundSympathetic overactivation and neuroinflammation in the paraventricular nucleus (PVN) are crucial factors in post–myocardial infarction (MI) cardiac remodeling and ventricular arrhythmias (VAs). Prior study has indicated that low-intensity focused ultrasound stimulation could attenuate sympathetic neuroinflammation within the PVN to prevent the occurrence of VAs in an acute MI model. Meanwhile, the cGAS-STING pathway has shown potential to ameliorate the neuroinflammatory response. However, the effect and mechanisms of long-term transcranial ultrasound stimulation (LTUS) for modulating neuroinflammation in the chronic stage of MI remain unclear. ObjectiveThis study aimed to ascertain whether LTUS could mitigate post-MI neuroinflammation and improve cardiac arrhythmia and remodeling through the cGAS-STING pathway. MethodsThirty-six SD rats were equally randomized to the sham group (pseudo-MI modeling), chronic MI group (MI modeling), and LTUS group (MI modeling and long-term ultrasound stimulation). Transcranial ultrasound stimulation (15 min/d) was conducted on the PVN for 4 consecutive weeks. After 4-week intervention, echocardiography, electrophysiologic experiments, and histopathologic staining were performed to assess the role of LTUS on post-MI neuroinflammation and cardiac remodeling. ResultsThe results indicated that LTUS significantly facilitated microglial M1 to M2 polarization through the cGAS-STING signaling pathway within the PVN. Furthermore, LTUS inhibited MI-induced sympathetic neuroinflammation, thereby improving cardiac dysfunction, ameliorating cardiac remodeling, and reducing VA inducibility. ConclusionLong-term ultrasound stimulation of the PVN was found to alleviate post-MI neuroinflammation and to improve cardiac remodeling, which might inspire novel insights and clinical strategies for noninvasive neuromodulation and the treatment of post-MI VAs.

In silico evaluation of cell therapy in acute versus chronic infarction: role of automaticity, heterogeneity and Purkinje in human

Human-based modelling and simulation offer an ideal testbed for novel medical therapies to guide experimental and clinical studies. Myocardial infarction (MI) is a common cause of heart failure and mortality, for which novel therapies are urgently needed. Although cell therapy offers promise, electrophysiological heterogeneity raises pro-arrhythmic safety concerns, where underlying complex spatio-temporal dynamics cannot be investigated experimentally. Here, after demonstrating credibility of the modelling and simulation framework, we investigate cell therapy in acute versus chronic MI and the role of cell heterogeneity, scar size and the Purkinje system. Simulations agreed with experimental and clinical recordings from ionic to ECG dynamics in acute and chronic infarction. Following cell delivery, spontaneous beats were facilitated by heterogeneity in cell populations, chronic MI due to tissue depolarisation and slow sinus rhythm. Subsequent re-entrant arrhythmias occurred, in some instances with Purkinje involvement and their susceptibility was enhanced by impaired Purkinje-myocardium coupling, large scars and acute infarction. We conclude that homogeneity in injected ventricular-like cell populations minimises their spontaneous beating, which is enhanced by chronic MI, whereas a healthy Purkinje-myocardium coupling is key to prevent subsequent re-entrant arrhythmias, particularly for large scars.

Microparticle Mediated Delivery of Apelin Improves Heart Function in Post Myocardial Infarction Mice.

Apelin is an endogenous prepropeptide that regulates cardiac homeostasis and various physiological processes. Intravenous injection has been shown to improve cardiac contractility in patients with heart failure. However, its short half-life prevents studying its impact on left ventricular remodeling in the long term. Here, we aim to study whether microparticle-mediated slow release of apelin improves heart function and left ventricular remodeling in mice with myocardial infarction (MI). A cardiac patch was fabricated by embedding apelin-containing microparticles in a fibrin gel scaffold. MI was induced via permanent ligation of the left anterior descending coronary artery in adult C57BL/6J mice followed by epicardial patch placement immediately after (acute MI) or 28 days (chronic MI) post-MI. Four groups were included in this study, namely sham, MI, MI plus empty microparticle-embedded patch treatment, and MI plus apelin-containing microparticle-embedded patch treatment. Cardiac function was assessed by transthoracic echocardiography. Cardiomyocyte morphology, apoptosis, and cardiac fibrosis were evaluated by histology. Cardioprotective pathways were determined by RNA sequencing, quantitative polymerase chain reaction, and Western blot. The level of endogenous apelin was largely reduced in the first 7 days after MI induction and it was normalized by day 28. Apelin-13 encapsulated in poly(lactic-co-glycolic acid) microparticles displayed a sustained release pattern for up to 28 days. Treatment with apelin-containing microparticle-embedded patch inhibited cardiac hypertrophy and reduced scar size in both acute and chronic MI models, which is associated with improved cardiac function. Data from cellular and molecular analyses showed that apelin inhibits the activation and proliferation of cardiac fibroblasts by preventing transforming growth factor-β-mediated activation of Smad2/3 (supporessor of mothers against decapentaplegic 2/3) and downstream profibrotic gene expression. Poly(lactic-co-glycolic acid) microparticles prolonged the apelin release time in the mouse hearts. Epicardial delivery of the apelin-containing microparticle-embedded patch protects mice from both acute and chronic MI-induced cardiac dysfunction, inhibits cardiac fibrosis, and improves left ventricular remodeling.

MRI Accurately Visualizes RF Ablation Delivery Targeted to MRI-Defined Arrhythmia Substrates in the Left Ventricle.

Investigate the capacity of MRI to evaluate efficacy of radiofrequency (RF) ablations delivered to MRI-defined arrhythmogenic substrates. Baseline MRI was performed at 3T including 3D LGE in a swine model of chronic myocardial infarct (N=8). MRI-derived maps of scar and heterogeneous tissue channels (HTCs) were generated using ADAS 3D. Animals underwent electroanatomic mapping and ablation of the left ventricle in CARTO3, guided by MRI-derived scar maps. Post-ablation MRI (in vivo at 3T in 5/8 animals; ex vivo at 1.5T in 3/8) included 3D native T1-weighted IR-SPGR (TI=700-800ms) to visualize RF lesions. T1-derived RF lesions were compared against excised tissue. The locations of T1-derived RF lesions were compared against CARTO ablation tags, and segment-wise sensitivity and specificity of lesion detection were calculated within the AHA 17-segment model. RF lesions were clearly visualized in HTCs, scar, and myocardium. Ablation patterns delivered in CARTO matched T1-derived RF lesion patterns with high sensitivity (88.9%) and specificity (94.7%), and were closely matched in registered MR-EP data sets, with a displacement of 5.4 ±3.8mm (N=152 ablation tags). Integrating MRI into ablative procedures for RF lesion assessment is feasible. Patterns of RF lesions created using a standard 3D EAM system are accurately reflected by MRI visualization in healthy myocardium, scar, and HTCs comprising the MRI-defined arrhythmia substrate. MRI visualization of RF lesions can provide near-immediate (<24h) assessment of ablation, potentially indicating whether critical MRI-defined ventricular tachycardia substrates have been adequately ablated.

Regional variation in technetium pyrophosphate (PYP) uptake in transthyretin cardiac amyloidosis (ATTR-CA) and concomitant myocardial infarction: A case series

- Diffuse and patchy myocardial uptake of Tc-99m PYP is well established in cases of ATTR-CA. - Chronic myocardial infarction leads to regional myocardial thinning and lack of vascular supply can present as regional sparing 'cold spot' on Tc-99m PYP imaging. - The absence of Tc-99m PYP uptake in vascular regions should raise the possibility of underlying scar.

Spatial and temporal tracking of multi-layered cells sheet using reporter gene imaging with human sodium iodide symporter: a preclinical study using a rat model of myocardial infarction.

This study aimed to evaluate a novel technique for cell tracking by visualising the activity of the human sodium/iodide symporter (hNIS) after transplantation of hNIS-expressing multilayered cell sheets in a rat model of chronic myocardial infarction. Triple-layered cell sheets were generated from mouse embryonic fibroblasts (MEFs) derived from mice overexpressing hNIS (hNIS-Tg). Myocardial infarction was induced by permanent ligation of the left anterior descending coronary artery in F344 athymic rats, and a triple-layered MEFs sheets were transplanted to the infarcted area two weeks after surgery. To validate the temporal tracking and kinetic analysis of the transplanted MEFs sheets, sequential cardiac single-photon emission computed tomography (SPECT) examinations with a 99mTcO4- injection were performed. The cell sheets generated using MEFs of wild-type mice (WT) served as controls. A significantly higher amount of 99mTcO4- was taken into the hNIS-Tg MEFs than into WT MEFs (146.1 ± 30.9-fold). The obvious accumulation of 99mTcO4- was observed in agreement with the region where hNIS-Tg MEFs were transplanted, and these radioactivities peaked 40-60min after 99mTcO4- administration. The volume of distribution of the hNIS-Tg MEF sheets declined gradually after transplantation, implying cellular malfunction and a loss in the number of transplanted cells. The reporter gene imaging with hNIS enables the serial tracking and quantitative kinetic analysis of cell sheets transplanted to infarcted hearts.

The cold temperature associated with new-onset heart failure after incorporating dynamic status of multimorbidity: nationwide cohort, Taiwan 2012-2019.

Cold temperatures are known to affect heart failure (HF) hospitalizations, but the dynamic status of multi-morbidity of HF was rarely incorporated. We investigated the relationship between temperature and new-onset HF by risk strata. This nationwide cohort study analysed daily data on ambient temperature, the dynamic status of risk factors (age, diabetes, chronic obstructive pulmonary disease, coronary artery disease, chronic kidney disease, hypertension, myocardial infarction, and atrial fibrillation), and new-onset HF among the Taiwan population from 2012 to 2019. Poisson regression, Austin's algorithm, and classification and regression tree (CART) were used to determine risk strata and obtain the predicted HF rate. 148 708 patients developed new-onset HF over 152.52 million person-years. Three risk strata for HF were identified: Stratum 1 was predominantly those without any comorbidity (89.9%); Stratum 2 was those aged 60-69 with 2-3 comorbidities or aged 70+ with 1-2 comorbidities (9.0%), and Stratum 3 was those aged 70+ and had four or more comorbidity (1.1%). The HF incidence rates for these three strata were 25.54, 555.27, and 2315.52 per 100 000 person-years, respectively. The R2 of the Poisson regression with the three risk strata and the daily minimum temperature on the ln HF incidence rates was 77.99%. The risk of HF increased as temperatures decreased, and the slopes were 1.032, 1.040, and 1.034 for Strata 1-3, respectively. The rate ratios of HF at the winter median temperature of 17°C vs. the summer median temperature of 29°C were 1.45, 1.58, and 1.49 for Strata 1-3, respectively. Cross-validation reveals a good fit and predicted HF rates by ambient temperature for the three strata were provided. Cold temperatures are associated with an increased risk of new-onset HF. Stratum 2 (aged 60-69 with 2-3 comorbidities or aged 70+ with 1-2 comorbidities) are particularly susceptible to cold-related new-onset HF.

Abstract We065: Sex Differences in Autoimmune Signatures After Myocardial Infarction in Mice

Introduction: Myocardial infarction (MI) is caused by ischemic injury to the left ventricle (LV), leading to an inflammatory response, scar formation, and loss of LV function. The role of the autoimmune (AI) response during chronic MI, such as B cell activation and autoantibody production, is not well understood. As AI disease is much more prevalent in females, we hypothesized that female mice are more susceptible to MI-induced development of AI signatures. Methods: Permanent MI was induced by left coronary artery ligation in adult male and female C57BL/6J mice for 7, 28, or 56 days. LV function was tracked using echocardiography (VEVO 3100). Cytokines were measured by qPCR. LV IgG and IgM antibody deposition was measured by immunofluorescence. Plasma IgG and IgM were measured by ELISA, and plasma autoantibodies (AABs) (IgG and IgM subclasses) were measured with an autoantigen (AAN) array. Results: In both sexes, MI led to progressive LV hypertrophy, dilation, and wall thinning. MI increased spleen mass in D7, 28, and 56 females, but decreased spleen mass in D28 and 56 males. LV infarct cytokines (IL-1β, IL-6, IL-18, IFN-γ, TNF, CCL2, IL-10) were increased at D7, while IL-6 and IL-18 remained elevated at D28 and 56 to a higher degree in females. Several cytokines in the remote LV were increased in females relative to males, including TNF, IL-6, CCL2, and IL-18. Splenic cytokines were also differentially expressed between sexes, with IL-1β, IL-12a, IL-10, IFN-γ, IL-18, CCL2, and IL-4 increased in females at several time points. Infarct IgG and IgM deposition occurred in both sexes, but to a higher degree in females. Remote IgG and IgM deposition occurred at D56 in both sexes. For plasma AABs, we detected 34 AANs against which IgG AABs were significantly elevated (p&lt;0.05) at D56 in females vs 9 in males, and 30 IgM AABs vs 1 in males. Of note, anti-IL-6 IgM AABs were elevated in D56 females (9.8±0.8-fold), likely due to persistently elevated IL-6 in the female infarct and remote LV vs males. Total levels of plasma IgM were increased only in females at D56 (1.79±0.15-fold). Conclusions: MI promotes development of AI signatures which is exacerbated in females, including increased spleen mass, LV and splenic cytokines, LV infarct and remote IgG and IgM antibody deposition, increased plasma IgG and IgM AABs, and increased total levels of plasma IgM. Targeting the AI response may be a viable option for treating chronic MI outcomes, particularly in females.

Abstract We008: Hallmark Maturation of the Human Pluripotent Stem Cells-derived Cardiovascular Progenitors in Myocardial Infarcted Large Animal Model

For the goal of regenerative cardiology, cellular therapy may be used to restore injured heart muscle. The molecular mechanisms behind the engraftment and maturation of these transplanted cells, however, remain poorly understood. Thus, to obtain a comprehensive understanding of the complex transcriptional landscapes within their transplanted spatial context, we utilized spatial transcriptomics in this study. We have previously demonstrated the safety and effectiveness of transplanting our cardiovascular progenitors (CVPs) produced from laminin-221 into pig hearts that had suffered myocardial infarction (MI). Here, we undertake 10x spatial transcriptomics in chronic MI pig models at 1-, 4-, and 12 weeks post-transplantation to further our understanding of these cells in vivo. With confidence, we can distinguish between the transcripts from the pigs and the humans in the infarcted region. By using human-specific anti-Ku80 antibodies for immunohistochemical labeling of the pig tissue samples, this in silico prediction was verified. The CVPs' engraftment and longevity in the infracted region were shown by the long-term identification and staining of human cells at various time points. It is interesting to note that after 12 weeks, ribosomal and mitochondrial activity were higher than at 1 and 2 weeks. These results are consistent with the hallmarks of cardiac maturation, in which cells transit from immature fetal-like cells to mature cardiomyocytes (CMs) by switching their metabolic energy source from glucose to fatty acids. Also, by comparing the heart-specific genes, including MYH6 and MYH7, we were able to quantify the myosin isoform switches in the xenograft over time. Furthermore, to delineate the fate of the transplanted cells, we performed a ligand-receptor interaction analysis. Intriguing, we identified the midkine protein as a possible secreted human paracrine factor that enhances angiogenesis in the graft. In conclusion, we have shown the successful engraftment and maturation of human CVPs toward CMs using spatial transcriptomic technology. These data will be used to understand other aspects of regenerative cardiology such as the mechanism of VTs and in vivo cellular repair mechanisms. A shiny app atlas has been generated to share our transcriptomics data for all to explore gene expression of human transplanted cells in myocardial infarcted pig hearts.

Enabling Reliable Visual Detection of Chronic Myocardial Infarction with Native T1 Cardiac MRI Using Data-Driven Native Contrast Mapping.

Purpose To investigate whether infarct-to-remote myocardial contrast can be optimized by replacing generic fitting algorithms used to obtain native T1 maps with a data-driven machine learning pixel-wise approach in chronic reperfused infarct in a canine model. Materials and Methods A controlled large animal model (24 canines, equal male and female animals) of chronic myocardial infarction with histologic evidence of heterogeneous infarct tissue composition was studied. Unsupervised clustering techniques using self-organizing maps and t-distributed stochastic neighbor embedding were used to analyze and visualize native T1-weighted pixel-intensity patterns. Deep neural network models were trained to map pixel-intensity patterns from native T1-weighted image series to corresponding pixels on late gadolinium enhancement (LGE) images, yielding visually enhanced noncontrast maps, a process referred to as data-driven native mapping (DNM). Pearson correlation coefficients and Bland-Altman analyses were used to compare findings from the DNM approach against standard T1 maps. Results Native T1-weighted images exhibited distinct pixel-intensity patterns between infarcted and remote territories. Granular pattern visualization revealed higher infarct-to-remote cluster separability with LGE labeling as compared with native T1 maps. Apparent contrast-to-noise ratio from DNM (mean, 15.01 ± 2.88 [SD]) was significantly different from native T1 maps (5.64 ± 1.58; P < .001) but similar to LGE contrast-to-noise ratio (15.51 ± 2.43; P = .40). Infarcted areas based on LGE were more strongly correlated with DNM compared with native T1 maps (R2 = 0.71 for native T1 maps vs LGE; R2 = 0.85 for DNM vs LGE; P < .001). Conclusion Native T1-weighted pixels carry information that can be extracted with the proposed DNM approach to maximize image contrast between infarct and remote territories for enhanced visualization of chronic infarct territories. Keywords: Chronic Myocardial Infarction, Cardiac MRI, Data-Driven Native Contrast Mapping Supplemental material is available for this article. © RSNA, 2024.

Precision imaging of cardiac function and scar size in acute and chronic porcine myocardial infarction using ultrahigh-field MRI

Background7 T cardiac magnetic resonance imaging (MRI) studies may enable higher precision in clinical metrics like cardiac function, ventricular mass, and more. Higher precision may allow early detection of functional impairment and early evaluation of treatment responses in clinical practice and pre-clinical studies. Methods: Seven female German Landrace pigs were scanned prior to and at three time points (3–4 days, 7–10 days, and ~60 days) post myocardial infarction using a whole body 7 T system and three radiofrequency (RF) coils developed and built in-house to accompany animal growth. Results: The combination of dedicated RF hardware and 7 T MRI enables a longitudinal study in a pig model of acute and chronic infarction, providing consistent blood tissue contrast and high signal-to-noise ratio (SNR) in measurements of cardiac function, as well as low coefficients of variation (CoV) for ejection fraction (CoVintra-observer: 2%, CoVinter-observer: 3.8%) and infarct size (CoVintra-observer: 8.4%, CoVinter-observer: 3.8%), despite drastic animal growth. Conclusions: Best results are achieved via manual segmentation. We define state-of-the-art procedures for large animal studies at 7 T.

Multinational evaluation of anthropometric age (AnthropoAge) as a measure of biological age in the USA, England, Mexico, Costa Rica, and China: a population-based longitudinal study.

To validate AnthropoAge, a new metric of biological age (BA), for prediction of all-cause mortality and age-related outcomes and characterize population-specific aging patterns using multinational longitudinal cohorts. We analyzed harmonized multinational data from the Gateway to Global Aging, including studies from the US, England, Mexico, Costa Rica, and China. We used body mass index and waist-to-height ratio to estimate AnthropoAge and AnthropoAgeAccel in participants aged 50-90 years old as proxies of BA and age acceleration, respectively. We compared the predictive capacity for all-cause mortality of AnthropoAge and chronological age (CA) using Cox models, described aging trends in all countries and explored the utility of longitudinal assessments of AnthropoAgeAccel to predict new-onset functional decline and age-related diseases using generalized estimating equations (GEE). Using data from 55,628 participants, we found AnthropoAge (c-statistic 0.772) outperformed CA (0.76) for prediction of mortality independently of comorbidities, sex, race/ethnicity, education, and lifestyle; this result was replicated in most countries individually except for Mexico. Individuals with accelerated aging had a ∼39% higher risk of death, and AnthropoAge also identified trends of faster biological aging per year. In longitudinal analyses, higher AnthropoAgeAccel values were independently predictive of self-reported health deterioration and new-onset deficits in basic/instrumental activities of daily living (ADL/IADL), diabetes, hypertension, cancer, chronic lung disease, myocardial infarction, and stroke. AnthropoAge is a robust and reproducible BA metric associated with age-related outcomes. Its implementation could facilitate modeling trends of biological aging acceleration in different populations, although recalibration may enhance its utility in underrepresented populations such as individuals from Latin America.

Long-Term Stimulation of the Left Dorsal Branch of the Thoracic Nerve Improves Ventricular Electrical Remodeling in a Canine Model of Chronic Myocardial Infarction.

To evaluate the ventricular electrophysiologic effects of long-term stimulation of the left dorsal branch of thoracic nerve (LDTN) derived from the left stellate ganglion (LSG) in a canine model of chronic myocardial infarction (MI). Seventeen adult male beagles were randomly divided into three groups: the sham group (sham operated, n = 6), the MI group (n = 6), and the MI + LDTN group (MI plus LDTN stimulation, n = 5). The canine model of chronic MI was induced by the occlusion of the left anterior descending artery (LADO). The LDTN was separated and intermittently stimulated immediately after LADO for 2months. The heart rate variability (HRV) analysis, in vivo electrophysiology, the evaluation of LSG function and neural activity, histological staining, and western blotting (WB) assay were performed to evaluate the effect of LDTN stimulation on the heart. The canine MI model was successfully established by LADO, and the LDTN was separated and stimulated immediately after LADO. The HRV analysis showed that LDTN stimulation reversed the increased LF value and LF/HF ratio of the MI group. LDTN stimulation prolonged the shortening ERP and APD90, decreased the dispersion of ERP and APD90, and increased the VFT. Additionally, LDTN stimulation inhibits the LSG function and neural activity. Furthermore, LDTN stimulation suppressed the activation of Wnt/β-catenin signaling, which contributed to the LSG neuronal apoptosis by upregulation of pro-apoptotic Bax and downregulation of anti-apoptotic Bcl-2. LDTN stimulation could attenuate cardiac sympathetic remodeling and improve ventricular electrical remodeling, which may be mediated by suppressing the activated Wnt/β-catenin signaling pathway and then promoting the LSG neuronal apoptosis.

Podoplanin Positive Cell-derived Extracellular Vesicles Contribute to Cardiac Amyloidosis After Myocardial Infarction.

Amyloidosis is a major long-term complication of chronic disease; however, whether it represents one of the complications of post-myocardial infarction (MI) is yet to be fully understood. Using wild-type and knocked-out MI mouse models and characterizing in vitro the exosomal communication between bone marrow-derived macrophages and activated mesenchymal stromal cells (MSC) isolated after MI, we investigated the mechanism behind Serum Amyloid A 3 (SAA3) protein overproduction in injured hearts. Here, we show that amyloidosis occurs after MI and that amyloid fibers are composed of macrophage-derived SAA3 monomers. SAA3 overproduction in macrophages is triggered by exosomal communication from a subset of activated MSC, which, in response to MI, acquire the expression of a platelet aggregation-inducing type I transmembrane glycoprotein named Podoplanin (PDPN). Cardiac MSC PDPN+ communicate with and activate macrophages through their extracellular vesicles or exosomes. Specifically, MSC PDPN+ derived exosomes (MSC PDPN+ Exosomes) are enriched in SAA3 and exosomal SAA3 protein engages with Toll-like receptor 2 (TRL2) on macrophages, triggering an overproduction and impaired clearance of SAA3 proteins, resulting in aggregation of SAA3 monomers as rigid amyloid deposits in the extracellular space. The onset of amyloid fibers deposition alongside extra-cellular-matrix (ECM) proteins in the ischemic heart exacerbates the rigidity and stiffness of the scar, hindering the contractility of viable myocardium and overall impairing organ function. Using SAA3 and TLR2 deficient mouse models, we show that SAA3 delivered by MSC PDPN+ exosomes promotes post-MI amyloidosis. Inhibition of SAA3 aggregation via administration of a retro-inverso D-peptide, specifically designed to bind SAA3 monomers, prevents the deposition of SAA3 amyloid fibrils, positively modulates the scar formation, and improves heart function post-MI. Overall, our findings provide mechanistic insights into post-MI amyloidosis and suggest that SAA3 may be an attractive target for effective scar reversal after ischemic injury and a potential target in multiple diseases characterized by a similar pattern of inflammation and amyloid deposition. What is known? Accumulation of rigid amyloid structures in the left ventricular wall impairs ventricle contractility.After myocardial infarction cardiac Mesenchymal Stromal Cells (MSC) acquire Podoplanin (PDPN) to better interact with immune cells.Amyloid structures can accumulate in the heart after chronic inflammatory conditions. What information does this article contribute? Whether accumulation of cumbersome amyloid structures in the ischemic scar impairs left ventricle contractility, and scar reversal after myocardial infarction (MI) has never been investigated.The pathophysiological relevance of PDPN acquirement by MSC and the functional role of their secreted exosomes in the context of post-MI cardiac remodeling has not been investigated.Amyloid structures are present in the scar after ischemia and are composed of macrophage-derived Serum Amyloid A (SAA) 3 monomers, although mechanisms of SAA3 overproduction is not established. Here, we report that amyloidosis, a secondary phenomenon of an already preexisting and prolonged chronic inflammatory condition, occurs after MI and that amyloid structures are composed of macrophage-derived SAA3 monomers. Frequently studied cardiac amyloidosis are caused by aggregation of immunoglobulin light chains, transthyretin, fibrinogen, and apolipoprotein in a healthy heart as a consequence of systemic chronic inflammation leading to congestive heart failure with various types of arrhythmias and tissue stiffness. Although chronic MI is considered a systemic inflammatory condition, studies regarding the possible accumulation of amyloidogenic proteins after MI and the mechanisms involved in that process are yet to be reported. Here, we show that SAA3 overproduction in macrophages is triggered in a Toll-like Receptor 2 (TLR2)-p38MAP Kinase-dependent manner by exosomal communication from a subset of activated MSC, which, in response to MI, express a platelet aggregation-inducing type I transmembrane glycoprotein named Podoplanin. We provide the full mechanism of this phenomenon in murine models and confirm SAA3 amyloidosis in failing human heart samples. Moreover, we developed a retro-inverso D-peptide therapeutic approach, "DRI-R5S," specifically designed to bind SAA3 monomers and prevent post-MI aggregation and deposition of SAA3 amyloid fibrils without interfering with the innate immune response.

Novel Fibrillar and Non-Fibrillar Collagens Involved in Fibrotic Scar Formation after Myocardial Infarction.

Following myocardial infarction (MI), adverse remodeling depends on the proper formation of fibrotic scars, composed of type I and III collagen. Our objective was to pinpoint the participation of previously unreported collagens in post-infarction cardiac fibrosis. Gene (qRT-PCR) and protein (immunohistochemistry followed by morphometric analysis) expression of fibrillar (types II and XI) and non-fibrillar (types VIII and XII) collagens were determined in RNA-sequencing data from 92 mice undergoing myocardial ischemia; mice submitted to permanent (non-reperfused MI, n = 8) or transient (reperfused MI, n = 8) coronary occlusion; and eight autopsies from chronic MI patients. In the RNA-sequencing analysis of mice undergoing myocardial ischemia, increased transcriptomic expression of collagen types II, VIII, XI, and XII was reported within the first week, a tendency that persisted 21 days afterwards. In reperfused and non-reperfused experimental MI models, their gene expression was heightened 21 days post-MI induction and positively correlated with infarct size. In chronic MI patients, immunohistochemistry analysis demonstrated their presence in fibrotic scars. Functional analysis indicated that these subunits probably confer tensile strength and ensure the cohesion of interstitial components. Our data reveal that novel collagens are present in the infarcted myocardium. These data could lay the groundwork for unraveling post-MI fibrotic scar composition, which could ultimately influence patient survivorship.

Myocardial infarction causes sex-dependent dysfunction in vagal sensory glutamatergic neurotransmission that is mitigated by 17β-estradiol.

Parasympathetic dysfunction after chronic myocardial infarction (MI) is known to predispose ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]). VT/VF after MI is more common in males than females. The mechanisms underlying the decreased vagal tone and the associated sex difference in the occurrence of VT/VF after MI remain elusive. In this study, using optogenetic approaches, we found that responses of glutamatergic vagal afferent neurons were impaired following chronic MI in male mice, leading to reduced reflex efferent parasympathetic function. Molecular analyses of vagal ganglia demonstrated reduced glutamate levels, accompanied by decreased mitochondrial function and impaired redox status in infarcted males versus sham animals. Interestingly, infarcted females demonstrated reduced vagal sensory impairment, associated with greater vagal ganglia glutamate levels and decreased vagal mitochondrial dysfunction and oxidative stress compared with infarcted males. Treatment with 17β-estradiol mitigated this pathological remodeling and improved vagal neurotransmission in infarcted male mice. These data suggest that a decrease in efferent vagal tone following MI results from reduced glutamatergic afferent vagal signaling that may be due to impaired redox homeostasis in the vagal ganglia, which subsequently leads to pathological remodeling in a sex-dependent manner. Importantly, estrogen prevents pathological remodeling and improves parasympathetic function following MI.