Cardiac function in a large animal model of myocardial infarction at 7 T: deep learning based automatic segmentation increases reproducibility.

Cardiac magnetic resonance (CMR) imaging allows precise non-invasive quantification of cardiac function. It requires reliable image segmentation for myocardial tissue. Clinically used software usually offers automatic approaches for this step. These are, however, designed for segmentation of human images obtained at clinical field strengths. They reach their limits when applied to preclinical data and ultrahigh field strength (such as CMR of pigs at 7 T). In our study, eleven animals (seven with myocardial infarction) underwent four CMR scans each. Short-axis cine stacks were acquired and used for functional cardiac analysis. End-systolic and end-diastolic images were labelled manually by two observers and inter- and intra-observer variability were assessed. Aiming to make the functional analysis faster and more reproducible, an established deep learning (DL) model for myocardial segmentation in humans was re-trained using our preclinical 7 T data (n = 772 images and labels). We then tested the model on n = 288 images. Excellent agreement in parameters of cardiac function was found between manual and DL segmentation: For ejection fraction (EF) we achieved a Pearson's r of 0.95, an Intraclass correlation coefficient (ICC) of 0.97, and a Coefficient of variability (CoV) of 6.6%. Dice scores were 0.88 for the left ventricle and 0.84 for the myocardium.

Parameter subset reduction for imaging-based digital twin generation of patients with left ventricular mechanical discoordination.

BACKGROUND: Integration of a patient's non-invasive imaging data in a digital twin (DT) of the heart can provide valuable insight into the myocardial disease substrates underlying left ventricular (LV) mechanical discoordination. However, when generating a DT, model parameters should be identifiable to obtain robust parameter estimations. In this study, we used the CircAdapt model of the human heart and circulation to find a subset of parameters which were identifiable from LV cavity volume and regional strain measurements of patients with different substrates of left bundle branch block (LBBB) and myocardial infarction (MI). To this end, we included seven patients with heart failure with reduced ejection fraction (HFrEF) and LBBB (study ID: 2018-0863, registration date: 2019-10-07), of which four were non-ischemic (LBBB-only) and three had previous MI (LBBB-MI), and six narrow QRS patients with MI (MI-only) (study ID: NL45241.041.13, registration date: 2013-11-12). Morris screening method (MSM) was applied first to find parameters which were important for LV volume, regional strain, and strain rate indices. Second, this parameter subset was iteratively reduced based on parameter identifiability and reproducibility. Parameter identifiability was based on the diaphony calculated from quasi-Monte Carlo simulations and reproducibility was based on the intraclass correlation coefficient ( ICC ) obtained from repeated parameter estimation using dynamic multi-swarm particle swarm optimization. Goodness-of-fit was defined as the mean squared error ( χ 2 ) of LV myocardial strain, strain rate, and cavity volume. RESULTS: A subset of 270 parameters remained after MSM which produced high-quality DTs of all patients ( χ 2 < 1.6), but minimum parameter reproducibility was poor ( ICC min = 0.01). Iterative reduction yielded a reproducible ( ICC min = 0.83) subset of 75 parameters, including cardiac output, global LV activation duration, regional mechanical activation delay, and regional LV myocardial constitutive properties. This reduced subset produced patient-resembling DTs ( χ 2 < 2.2), while septal-to-lateral wall workload imbalance was higher for the LBBB-only DTs than for the MI-only DTs (p < 0.05). CONCLUSIONS: By applying sensitivity and identifiability analysis, we successfully determined a parameter subset of the CircAdapt model which can be used to generate imaging-based DTs of patients with LV mechanical discoordination. Parameters were reproducibly estimated using particle swarm optimization, and derived LV myocardial work distribution was representative for the patient's underlying disease substrate. This DT technology enables patient-specific substrate characterization and can potentially be used to support clinical decision making.

In Vivo Mapping of Myocardial Injury Outside the Infarct Zone: Tissue at an Intermediate Pathological State.

BACKGROUND: The goal was to determine the feasibility of mapping the injured-but-not-infarcted myocardium using 99mTc-duramycin in the postischemic heart, with spatial information for its characterization as a pathophysiologically intermediate tissue, which is neither normal nor infarcted. METHODS AND RESULTS: Coronary occlusion was conducted in Sprague Dawley rats with preconditioning and 30-minute ligation. In vivo single-photon emission computed tomography was acquired after 3 hours (n=6) using 99mTc-duramycin, a phosphatidylethanolamine-specific radiopharmaceutical. The 99mTc-duramycin+ areas were compared with infarct and area-at-risk (n=8). Cardiomyocytes and endothelial cells were isolated for gene expression profiling. Cardiac function was measured with echocardiography (n=6) at 4 weeks. In vivo imaging with 99mTc-duramycin identified the infarct (3.9±2.4% of the left ventricle and an extensive area 23.7±2.2% of the left ventricle) with diffuse signal outside the infarct, which is pathologically between normal and infarcted (apoptosis 1.8±1.6, 8.9±4.2, 13.6±3.8%; VCAM-1 [vascular cell adhesion molecule 1] 3.2±0.8, 9.8±4.1, 15.9±4.2/mm2; tyrosine hydroxylase 14.9±2.8, 8.6±4.4, 5.6±2.2/mm2), with heterogeneous changes including scattered micronecrosis, wavy myofibrils, hydropic change, and glycogen accumulation. The 99mTc-duramycin+ tissue is quantitatively smaller than the area-at-risk (26.7% versus 34.4% of the left ventricle, P=0.008). Compared with infarct, gene expression in the 99mTc-duramycin+-noninfarct tissue indicated a greater prosurvival ratio (BCL2/BAX [B-cell lymphoma 2/BCL2-associated X] 7.8 versus 5.7 [cardiomyocytes], 3.7 versus 3.2 [endothelial]), and an upregulation of ion channels in electrophysiology. There was decreased contractility at 4 weeks (regional fractional shortening -8.6%, P<0.05; circumferential strain -52.9%, P<0.05). CONCLUSIONS: The injured-but-not-infarcted tissue, being an intermediate zone between normal and infarct, is mapped in vivo using phosphatidylethanolamine-based imaging. The intermediate zone contributes significantly to cardiac dysfunction.

Simultaneous Viability Assessment and Invasive Coronary Angiography Using a Therapeutic CT System in Chronic Myocardial Infarction Patients.

PURPOSE: In a preclinical study using a swine myocardial infarction (MI) model, a delayed enhancement (DE)-multi-detector computed tomography (MDCT) scan was performed using a hybrid system alongside diagnostic invasive coronary angiography (ICA) without the additional use of a contrast agent, and demonstrated an excellent correlation in the infarct area compared with histopathologic specimens. In the present investigation, we evaluated the feasibility and diagnostic accuracy of a myocardial viability assessment by DE-MDCT using a hybrid system comprising ICA and MDCT alongside diagnostic ICA without the additional use of a contrast agent. MATERIALS AND METHODS: We prospectively enrolled 13 patients (median age: 67 years) with a previous MI (>6 months) scheduled to undergo ICA. All patients underwent cardiac magnetic resonance (CMR) imaging before diagnostic ICA. MDCT viability scans were performed concurrently with diagnostic ICA without the use of additional contrast. The total myocardial scar volume per patient and average transmurality per myocardial segment measured by DE-MDCT were compared with those from DE-CMR. RESULTS: The DE volume measured by MDCT showed an excellent correlation with the volume measured by CMR (r=0.986, p<0.0001). The transmurality per segment by MDCT was well-correlated with CMR (r=0.900, p<0.0001); the diagnostic performance of MDCT in differentiating non-viable from viable myocardium using a 50% transmurality criterion was good with a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 87.5%, 99.5%, 87.5%, 99.5%, and 99.1%, respectively. CONCLUSION: The feasibility of the DE-MDCT viability assessment acquired simultaneously with conventional ICA was proven in patients with chronic MI using DE-CMR as the reference standard.

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.).

Acute myocardial infarction due to giant coronary artery aneurysm and arteriovenous fistula: a challenging case report and review of the literature.

BACKGROUND: A coronary artery aneurysm (CAA) is an abnormal dilation of a coronary artery segment often accompanied by coronary artery fistula (CAF), leading to communication between a coronary artery and a cardiac chamber or a part of the coronary venous system. Both CAAs and CAFs can present with symptoms and signs of myocardial ischemia and infarction. CASE PRESENTATION: We describe the case of a 46-year-old woman with non-ST-elevation myocardial infarction (NSTEMI) caused by a "giant" CAA. Various imaging modalities revealed a thrombus-containing aneurysm located at the right-posterior cardiac border, with established arteriovenous communication with the distal part of left circumflex artery (LCx). After initial treatment with dual antiplatelet therapy, a relapse of pain was reported along with a new increase in troponin levels, electrocardiographic abnormalities, reduced left ventricular ejection fraction (LVEF) and thrombus enlargement. Surgical excision of the aneurysm was favored, revealing its true size of 6 cm in diameter. Τhe aneurysm was excised without complications. The patient remained asymptomatic during follow-up. CONCLUSIONS: Management of rare entities such as "giant" CAAs and CAFs can be challenging. Cases such as this can serve as precedents to facilitate treatment plans and develop consistent recommendations, emphasizing the importance of personalized strategies for future patients.

Influence of sex on the timing of coronary angiography and the prescription of antiplatelet therapy in patients with nonST-segment elevation myocardial infarction. / Impacto del sexo en los tiempos de cateterismo y en el uso de pretratamiento antiagregante plaquetario en pacientes con síndrome coronario agudo sin elevación del segmento ST (SCASEST).

OBJECTIVES: To assess differences in the clinical management of nonST-segment elevation myocardial infarction (NSTEMI), including in-hospital events, according to biological sex. MATERIAL AND METHODS: Prospective observational multicenter study of patients diagnosed with NSTEMI and atherosclerosis who underwent coronary angiography. RESULTS: We enrolled 1020 patients in April and May 2022; 240 (23.5%) were women. Women were older than men on average (72.6 vs 66.5 years, P .001), and more women were frail (17.1% vs 5.6%, P .001). No difference was observed in pretreatment with any P2Y12 inhibitor (prescribed in 68.8% of women vs 70.2% of men, P = .67); however, more women than men were prescribed clopidogrel (56% vs 44%, P = .009). Women prescribed clopidogrel were more often under the age of 75 years and not frail. Coronary angiography was performed within 24 hours less corooften in women (29.8% vs 36.9%, P = .03) even when high risk was recognized. Frailty was independently associated with deferring coronary angiography in the adjusted analysis; biological sex by itself was not related. The frequency and type of revascularization were the same in both sexes, and there were no differences in in-hospital cardiovascular events. CONCLUSION: Women were more often prescribed less potent antithrombotic therapy than men. Frailty, but not sex, correlated independently with deferral of coronary angiography. However, we detected no differences in the frequency of coronary revascularization or in-hospital events according to sex.

OBJETIVO: Evaluar las diferencias en el manejo clínico y eventos intrahospitalarios en una cohorte de pacientes con síndrome coronario agudo sin elevación del segmento ST (SCASEST) en función del sexo. METODO: Estudio observacional, prospectivo y multicéntrico que incluyó pacientes consecutivos con diagnóstico de SCASEST sometidos a coronariografía con enfermedad ateroesclerótica responsable. RESULTADOS: Entre abril y mayo de 2022 se incluyeron 1.020 pacientes; de ellos, 240 eran mujeres (23,5%). En comparación con los hombres, las mujeres fueron mayores (72,6 años vs 66,5 años; p 0,001) y más frágiles (17,1% vs 5,6%; p 0,001). No hubo diferencias en el pretratamiento con un inhibidor del receptor P2Y12 (68,8% vs 70,2%, p = 0,67), aunque las mujeres recibieron más pretratamiento con clopidogrel (56% vs 44%, p = 0,009), principalmente aquellas de edad 75 años y sin fragilidad. En las mujeres se realizaron menos coronariografías precoces (# 24 h) (29,8% vs 36,9%; p = 0,03) a pesar de presentar la misma indicación (criterios de alto riesgo). En el análisis ajustado, la fragilidad, pero no el sexo, se asoció de forma independiente con la realización de una coronariografía diferida. La tasa y el tipo de revascularización fue igual en ambos sexos, y no hubo diferencias en los eventos cardiovasculares intrahospitalarios. CONCLUSIONES: Las mujeres recibieron con mayor frecuencia un tratamiento antitrombótico menos potente. La fragilidad y no el sexo se asoció con la realización de coronariografía diferida. Sin embargo, no hubo diferencias en la tasa de revascularización coronaria ni en los eventos intrahospitalarios en función del sexo.

Remotely Triggered LAD Occlusion Using a Balloon Catheter in Spontaneously Breathing Mice.

Acute myocardial infarction (AMI) is a prevalent and high-mortality cardiovascular condition. Despite advancements in revascularization strategies for AMI, it frequently leads to myocardial ischemia-reperfusion injury (IRI), amplifying cardiac damage. Murine models serve as vital tools for investigating both acute injury and chronic myocardial remodeling in vivo. This study presents a unique closed-chest technique for remotely inducing myocardial IRI in mice, enabling the investigation of the very early phase of occlusion and reperfusion using in-vivo imaging such as MRI or PET. The protocol utilizes a remote occlusion method, allowing precise control over ischemia initiation after chest closure. It reduces surgical trauma, enables spontaneous breathing, and enhances experimental consistency. What sets this technique apart is its potential for simultaneous noninvasive imaging, including ultrasound and magnetic resonance imaging (MRI), during occlusion and reperfusion events. It offers a unique opportunity to analyze tissue responses in almost real-time, providing critical insights into processes during ischemia and reperfusion. Extensive systematic testing of this innovative approach was conducted, measuring cardiac necrosis markers for infarction, assessing the area at risk using contrast-enhanced MRI, and staining infarcts at the scar maturation stage. Through these investigations, emphasis was placed on the value of the proposed tool in advancing research approaches to myocardial ischemia-reperfusion injury and accelerating the development of targeted interventions. Preliminary findings demonstrating the feasibility of combining the proposed innovative experimental protocol with noninvasive imaging techniques are presented herein. These initial results highlight the benefit of utilizing the purpose-built animal cradle to remotely induce myocardial ischemia while simultaneously conducting MRI scans.

Prognostic impact of carotid plaque imaging using total plaque area added to SCORE2 in middle-aged subjects: the ARteris Cardiovascular Outcome (ARCO) cohort study.

AIMS: Many cardiovascular events occur in seemingly healthy individuals.We set out to assess the predictive value of atherosclerosis imaging in combination with cardiovascular risk calculators in subjects aged 40-65 years. METHODS: We compared PROCAM (PROspective CArdiovascular Münster study), SCORE (Systematic COronary Risk Evaluation) and SCORE2 with carotid ultrasound (total plaque area, TPA) in subjects without cardiovascular disease. In this prospective cohort study, follow-up was obtained by phone or mail from patients; or from clinical records, if needed. RESULTS: In 2842 subjects (mean age 50±8 years; 38% women), cardiovascular events occurred in 154 (5.4%) of them over an mean follow-up period of 5.9 (range 1-12) years, specifically: 41 cases of AMI (myocardial infarction), 16 strokes, 21 CABG (coronary artery bypass grafting), 41 PTCA (percutaneous transluminal coronary angioplasty) and 35 CAD (coronary artery disease). Mean PROCAM risk was 5±6%, mean SCORE risk was 1.3±1.6% and mean SCORE2 risk was 5±3%. Both for the primary outcome (major adverse cardiovascular events, MACEs, i.e. AMI + strokes) and the secondary outcome (atherosclerotic cardiovascular disease, ASCVD, i.e. MACEs + CABG + CAD + PTCA), hazards increased significantly for TPA tertiles and SCORE2 post-test risk between 6.7 to 12.8 after adjustment for risk factors (age, smoke, sex, systolic blood pressure, lipids, medication) and after adjustment for results from PROCAM, SCORE and SCORE2. Model performance was statistically improved regarding model fit in all models using TPA. Net reclassification improvement for SCORE2 with TPA post-test risk increased significantly by 24% for MACEs (p = 0.01) and 39% for ASCVD (p <0.0001). CONCLUSIONS: Integration of TPA post-test risk into SCORE2 adds prognostic information, supporting the use of carotid ultrasound when assessing ASCVD risk in subjects aged 40-65 years.

Effects of alirocumab on endothelial function and coronary atherosclerosis in myocardial infarction: A PACMAN-AMI randomized clinical trial substudy.

BACKGROUND AND AIMS: The effects of protein convertase subtilisin/kexin type 9 (PCSK9) inhibitors on endothelial function as assessed by flow-mediated dilation (FMD) in patients with acute myocardial infarction (AMI) are unknown. Therefore, we aimed to investigate the effects of the PCSK9 inhibitor alirocumab added to high-intensity statin on FMD, and its association with coronary atherosclerosis in non-infarct related arteries using intracoronary intravascular ultrasound (IVUS), near-infrared spectroscopy (NIRS), and optical coherence tomography (OCT). METHODS: This was a pre-specified substudy among patients recruited at Bern University Hospital, Switzerland, for the randomized-controlled, double-blind, PACMAN-AMI trial, which compared the effects of biweekly alirocumab 150 mg vs. placebo added to rosuvastatin. Brachial artery FMD was measured at 4 and 52 weeks, and intracoronary imaging at baseline and 52 weeks. RESULTS: 139/173 patients completed the substudy. There was no difference in FMD at 52 weeks in the alirocumab (n = 68, 5.44 ± 2.24%) versus placebo (n = 71, 5.45 ± 2.19%) group (difference = -0.21%, 95% CI -0.77 to 0.35, p = 0.47). FMD improved throughout 52 weeks in both groups similarly (p < 0.001). There was a significant association between 4 weeks FMD and baseline plaque burden (IVUS) (n = 139, slope = -1.00, p = 0.006), but not with lipid pool (NIRS) (n = 139, slope = -7.36, p = 0.32), or fibrous cap thickness (OCT) (n = 81, slope = -1.57, p = 0.62). CONCLUSIONS: Among patients with AMI, the addition of alirocumab did not result in further improvement of FMD as compared to 52 weeks secondary preventative medical therapy including high-intensity statin therapy. FMD was significantly associated with coronary plaque burden at baseline, but not with lipid pool or fibrous cap thickness.

Acoustic Activation Imaging With Intravenous Perfluoropropane Nanodroplets Results in Selective Bioactivation of the Risk Area.

BACKGROUND: Acoustically activatable perfluoropropane droplets (PD) can be formulated from commercially available microbubble preparations. Diagnostic transthoracic ultrasound frequencies have resulted in acoustic activation (AA) predominately within myocardial infarct zones (IZ). OBJECTIVE: We hypothesized that the AA area following acute coronary ischemia/reperfusion (I/R) would selectively enhance the developing scar zone, and target bioeffects specifically to this region. METHODS: We administered intravenous PD in 36 rats and 20 pigs at various stages of myocardial scar formation (30 minutes, 1 day, and 7 days post I/R) to determine what effect infarct age had on the AA within the IZ. This was correlated with histology, myeloperoxidase activity, and tissue nitrite activity. RESULTS: The degree of AA within the IZ in rats was not associated with collagen content, neutrophil infiltration, or infarct age. AA within 24 hours of I/R was associated with increased nitric oxide utilization selectively within the IZ (P < .05 compared with remote zone). The spatial extent of AA in pigs correlated with infarct size only when performed before sacrifice at 7 days (r = .74, P < .01). CONCLUSIONS: Acoustic activation of intravenous PD enhances the developing scar zone following I/R, and results in selective tissue nitric oxide utilization.

Paclitaxel-induced acute myocardial infarction: a case report and literature review.

BACKGROUND: Paclitaxel is a chemotherapeutic agent commonly used for ovarian, lung, breast carcinoma, and Kaposi's sarcoma. Its common side effects include hypersensitivity reaction, bone marrow suppression, and peripheral neuropathy. However, a rare and life-threatening side effect is paclitaxel-induced myocardial infarction. CASE PRESENTATION: A 71-year-old man with type 2 diabetes mellitus, hypertension, heavy smoking history, previous coronary artery disease with percutaneous coronary intervention (PCI) in left anterior descending artery (LAD), and non-small lung cancer presented with non-ST elevation myocardial infarction during infusion of paclitaxel infusion. Coronary angiogram showed de novo three vessel disease with 70% stenosis in ostial to distal left main artery (LM) and 80% in-stent re-stenosis in proximal to mid left anterior descending artery. CONCLUSIONS: Physicians should be keeping this in mind when dealing with patients on paclitaxel, especially if they have previous risk factors for coronary artery disease.

Methodology for the induction of myocardial infarction and cardiac function evaluation.

Cardiovascular disease (CVD) is the main cause of death worldwide, with myocardial infarction (MI) being the most prevalent pathology involved in CVD. MI is characterized by a deficiency in oxygen supply to the myocardium, thereby promoting ventricular remodeling of the ischemic and remote zone of the heart. Cardiac remodeling associated with MI could promote the development of heart failure and finally death. For these reasons, it is important to develop animal models that mimic human cardiac disease which could help to identify new mechanisms involved in the pathology and, consequently, develop new therapeutic strategies. We herein describe in detail a protocol for MI induction with low mortality rate (<15%) in rats by ligation of the left anterior descending artery. In addition, we also describe two imaging techniques which allow to evaluate cardiac structure and function-including deformation parameters in rats such as transthoracic echocardiography and cardiac magnetic resonance. This animal model could be useful for acute and chronic studies and for evaluating the potential usefulness of different treatments.