Stress and its associated factors in mothers with preterm infants in a private tertiary care hospital of Karachi, Pakistan: an analytical cross-sectional study

Objectives
This goal of this research is to present a comprehensive method for evaluating stress and the factors that contribute to it in mothers of premature babies.

Design
Analytical cross-sectional study.

Setting
Data were collected from inpatient service for preterm infants including neonatal intensive care unit, and neonatal step-down units of the Aga Khan University Hospital—a private tertiary care hospital in Karachi, Pakistan.

Participants
Mothers aged 18 years and above who delivered preterm infants (gestational age of preterm below 37 weeks) in a private tertiary care hospital in Karachi, Pakistan.

Primary outcome
Stress in mothers of preterm infants.

Results
200 participants with a mean age of 30.12 years (SD ±5.21) were assessed. The level of stress identified using the perceived stress scale (PSS) among mothers who had delivered preterm infants was significantly higher as compared with other countries around the world. Based on the criteria of PSS scoring, the majority of the participants (92%, n=184) were categorised as having high perceived stress and 8% (n=16) of the mothers fell into the category of moderate stress.

Conclusions
The study findings suggest high levels of perceived stress among mothers of preterm infants. The factors associated with the stress among mothers of preterm infants included immunisation of newborn, education and occupation status of mothers, substance abuse by mother, gender preference from family, planning for further children, consumption of balance diet, education status of husband, mode of socialisation, years of marriage and hours of sleep.

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Novembre 2024

Preference of mHealth versus in-person treatment for depression and post-traumatic stress disorder in Kenya: demographic and clinical characteristics

Objectives
We conducted an implementation science mental health treatment study in western Kenya, testing strategies for scale up of evidence-based mental health services for common adult disorders using a non-specialist workforce, integrated with existing primary care (Sequential Multiple, Assignment Randomized Trial of non-specialist-delivered psychotherapy (Interpersonal Psychotherapy) and/or medication (fluoxetine) for major depression and post-traumatic stress disorder (PTSD) (SMART DAPPER)). Because study launch coincided with the COVID-19 pandemic, participants were allowed to attend treatment visits via mHealth (audio-only mobile phone) or in-person. We conducted a secondary data analysis of the parent study to evaluate preference for mHealth or in-person treatment among our study participants, including rationale for choosing in-person or mHealth treatment modality, and comparison of baseline demographic and clinical characteristics.

Design, setting, participants and interventions
Participants were public sector primary care patients at Kisumu County Hospital in western Kenya with major depression and/or PTSD and were individually randomised to non-specialist delivery of evidence-based psychotherapy or medication (n=2162).

Outcomes
Treatment modality preference and rationale were ascertained before randomised assignment to treatment arm (psychotherapy or medication). The parent SMART DAPPER study baseline assessment included core demographic (age, gender, relationship status, income, clinic transport time and cost) and clinical data (eg, depression and PTSD symptoms, trauma exposures, medical comorbidities and history of mental healthcare). Given that this evaluation of mHealth treatment preference sought to identify the demographic and clinical characteristics of participants who chose in-person or mHealth treatment modality, we included most SMART DAPPER core measurement domains (not all subcategories).

Results
649 (30.3%) SMART DAPPER participants preferred treatment via mHealth, rather than in person. The most cited rationales for choosing mHealth were affordability (18.5%) (eg, no transportation cost) and convenience (12.9%). On multivariate analysis, compared with those who preferred in-person treatment, participants who chose mHealth were younger and had higher constraints on receiving in-person treatment, including transport time 1.004 (1.00, 1.007) and finances 0.757 (0.612, 0.936). Higher PTSD symptoms 0.527 (0.395, 0.702) and higher disability 0.741 (0.559, 0.982) were associated with preference for in-person treatment.

Conclusions
To our knowledge, this is the first study of public sector mental healthcare delivered by non-specialists via mHealth for major depression and/or PTSD in Sub-Saharan Africa. Our finding that mHealth treatment is preferred by approximately one-third of participants, particularly younger individuals with barriers to in-person care, may inform future mHealth research to (1) address knowledge gaps in mental health service implementation and (2) improve mental healthcare access to evidence-based treatment.

Trial registration number
NCT03466346.

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Novembre 2024

Abstract 4146301: Relationship Between Calf Muscle Pump Function and Exercise Stress Testing

Circulation, Volume 150, Issue Suppl_1, Page A4146301-A4146301, November 12, 2024. Background:Exercise stress testing uses metabolic equivalents of tasks (METs) to measure the energy cost of activities, aiding in the assessment of exercise capacity and cardiovascular health. Despite its significance, the correlation between calf muscle pump function (CPF) and exercise stress testing remains unexplored. We aimed to evaluate the relationship between CPF and peak METs as determined by cardiopulmonary treadmill exercise stress testing.Methods:The study included adults who underwent exercise cardiopulmonary stress testing and venous plethysmography at Mayo Clinic between April 2017 and March 2020. The protocols other than Bruce, Mayo, Modified Naughton, and Naughton protocols were excluded. The CPF ejection fraction (EF) was calculated per leg based on refill volumes post-exercise as a percentage of passive drain refill. The classification of CEAP (Clinical-Etiology-Anatomy-Pathophysiology) was utilized to better understand chronic venous insufficiency (CVI).Results:A total of 155 patients who underwent both exercise stress testing and venous plethysmography were included, with a mean age of 61.31 ± 14.03 years, and 84 (54.2%) were male. The peak measured METs for normal, unilaterally reduced, and bilaterally reduced CPF were 8.5 (2.5), 7.3 (2.1), and 7.1 (2.4), respectively (p=0.004, Figure 1). Multiple linear regression models were developed with METs as the outcome to determine if CPF was an independent predictor of METs on cardiopulmonary exercise stress testing. IIn model 1, the following independent variables were included: resting heart rate, peak heart rate, peak systolic blood pressure, recovery heart rate at minute 1, and worst EF (Table 1). In model 1, with only exercise parameters, lower EF was associated with lower METs (p=0.03). In a second analysis, variables identified as statistically significant with METs in the initial model were included, along with CEAP class (model 2) and CCI (model 3) (Table 2). In model 2, CEAP class 3 or higher was associated with decreased METs on the exercise stress test. This correlation implies that individuals with moderate to severe CVI may influence exercise capacity, demonstrating the interconnectedness of the cardiovascular system. Moreover, in model 3, the CCI, a predictor for mortality, was not significantly associated with METs.Conclusion:Our findings revealed that more severe CVI (CEAP class and reduced CPF) was associated with reduced exercise capacity after accounting for other factors.

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Novembre 2024

Abstract 4139170: Relationship between hemodynamics and oxygen consumption in hypertrophic cardiomyopathy during maximal stress testing

Circulation, Volume 150, Issue Suppl_1, Page A4139170-A4139170, November 12, 2024. Background:Hypertrophic cardiomyopathy (HCM) is a global heart disease with great variability in disease severity, which can lead to significant impairment of exercise capacity. In healthy populations, oxygen consumption is related to cardiac output and arteriovenous oxygen difference. We sought to determine the relationship between hemodynamics (cardiac output and stroke volume) and oxygen consumption in HCM compared to healthy controls during maximal stress testing.Aims:To evaluate associations between the trajectories of hemodynamic function and oxygen consumption in HCM compared to healthy controls.Methods:Twenty individuals with HCM (51±15 years old, body mass index (BMI): 28±3 kg/m2, females, n=4) and 16 healthy controls (66±7 years old, 27±6 kg/m2, females, n=6) were included in the present study. Participants completed a maximal-graded stress test coupled with non-invasive hemodynamic bioreactance (cardiac output, stroke volume) and gas exchange (oxygen consumption, VO2) measurements. Data were analyzed in quartiles (exercise only) and phases (rest, pre-pedalling, exercise and recovery) of the maximal-graded stress test.Results:In HCM, cardiac output declined in the fourth quartile of the exercise phase of the stress test (-0.39 L/min,p

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Novembre 2024

Abstract 4114705: Clinical Predictors of Stress Induced Cardiomyopathy

Circulation, Volume 150, Issue Suppl_1, Page A4114705-A4114705, November 12, 2024. Introduction:Stress Induced Cardiomyopathy is increasingly becoming more prevalent with increasing awareness about disease condition with annual incidence of 30 cases/100000 per year and an incidence of 1-2% in the patients presenting with acute coronary syndrome.[1] Physical and emotional triggers have been linked with occurrence of Stress induced Cardiomyopathy.Methods:We have obtained the National Readmission database for the year of 2020. We have used the ICD 10 code I51.81 for stress induced cardiomyopathy and found 10450 patients in the data base. Total 494 patients had cardiac arrest and 191 patients out of this 494 had died. We have used Binary logistic regression methods to find the odd ratio for physical and emotional risk factors for stress induced cardiomyopathy.Results:Grief disorder with an odd ratio of 7.2, followed by female gender with an odd ratio of 4.1, septic shock with an odd ratio of 3.3, Hemorrhagic stroke with an odd ratio of 1.73, ischemic stroke with an odd ratio of 1.72, depression with an odd ratio of 1.5, followed by asthma exacerbation with an odd ratio of 1.35 and seizure disorder with an odd ratio of 1.34 were among the few predictors for stress induced cardiomyopathy. Incidence of Cardiac Arrest was 4.7% and mortality rate of 1.8% was observed in the patients with stress induced Cardiomyopathy.Discussion:Extreme emotional and physical triggers like stroke, septic shock are among few significant risk factors for the stress induced cardiomyopathy.

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Novembre 2024

Abstract 4141446: Sodium Glucose Co-transporter 2 (SGLT2) Inhibitors Promote Resiliency to High Pressure Stress in the Human Microvasculature

Circulation, Volume 150, Issue Suppl_1, Page A4141446-A4141446, November 12, 2024. Emerging evidence suggests that vascular stress from cardiovascular-related co-morbidities promotes microvascular dysfunction, a key component in the development of heart failure with preserved ejection fraction. The sodium glucose co-transporter 2 (SGLT2) inhibitor empagliflozin has been shown to reduce both morbidity and mortality associated with heart failure with preserved ejection fraction, however the full scope of influence of this therapy on human microvascular function remains unknown. We hypothesized that pre-treatment of isolated human microvessels with empagliflozin will prevent stress-induced endothelial dysfunction as evidenced by preserving both the magnitude of flow-induced dilation (FID) as well as the ability to dilate to nitric oxide. Human resistance arterioles (80-250µm) from healthy adults (defined as patients with ≤1 risk factor for cardiovascular disease) were dissected from discarded surgical adipose tissue and treated with empagliflozin (1µM), or vehicle control (ethanol) for 16-20 hours prior to the flow experiment. Vessels were cannulated for videomicroscopy and subjected to high intraluminal pressure (150mmHg, 30 min), an acute stress known to induce endothelial dysfunction. Vessels were pre-constricted with endothelin-1 prior to initiation of flow. A nonlinear logistic regression was used to determine differences between curves. Compared to vehicle control, vessels pre-treated with empagliflozin (1µM ) exhibited nitric oxide-dependent FID as dilation was impaired in the presence of the nitric oxide synthase inhibitor L-NAME (EC50 Control: 10.7 vs L-NAME 83.45, p=0.0107). This data suggests that empagliflozin, an SGLT2 inhibitor, promotes microvascular resilience to stress via preservation of nitric oxide-mediated FID. The ability to elicit stress resilience may explain in part some of the cardiovascular benefits associated with SGLT2 inhibitors and may offer unique opportunities for early intervention or prevention of microvascular dysfunction associated with comorbidities that contribute to heart failure with preserved ejection fraction.

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Novembre 2024

Abstract 4147602: The Paradox Role of Sirtuin 6 In Coronary Microvascular Function under Metabolic Stress

Circulation, Volume 150, Issue Suppl_1, Page A4147602-A4147602, November 12, 2024. Coronary microvascular dysfunction (CMD), which is associated with diabetic cardiomyopathy, Takotsubo cardiomyopathy, andheart failure with preserved ejection fraction (HFpEF), is understudied. CMD is characterized by impaired endothelial-dependent vasodilation, but detailed mechanisms have yet to be elucidated.Nuclear Sirtuin 6 (SIRT6) plays essential roles in gene transcriptional, stress tolerance, DNA repair, inflammation, and aging. SIRT6 is strongly associated with cardiovascular pathologies, but how SIRT6 regulates endothelial metabolisms and homeostasis under metabolic stress and the underlying mechanism remains poorly understood. It might be because global Sirt6 knockout mice are perinatally lethal caused by hypoglycemia, suggesting the essential role of SIRT6 in glucose metabolism.In our preliminary studies, we generated inducible global Sirt6 knockout mice by crossing with Sirt6 f/f mice with CAG-cre (Sirt6f/f, CAG), and mice were viable with normal glucose levels. However, they showed impaired endothelial-dependent dilation (EDD) and impaired coronary flow reserve (CFR), an index clinically used to diagnose CMD. It suggests that deletion of Sirt6 might cause EC dysfunction because Sirt6 is reported to protect EC from premature senescence and oxidative stress by sustaining high eNOS levels. Surprisingly, when we studied non-inducible Sirt6 endothelial-specific knockout (Sirt6f/f, tie-2 cre) and inducible Sirt6 endothelial-specific knockout (Sirt6 f/f,Cdh5-cre/ERT2) and wild-type (WT) mice, Sirt6f/f, Tie-2and Sirt6f/f, Cadh5mice do not phenocopy the inducible global SIRT6 knockout mice, they had normal EDD and CFR. When the mice were fed a high fat and high sugar (HFHS) diet, the Sirt6f/f, Tie-2and Sirt6f/f, Cadh5had impaired EDD, suggesting Sirt 6 functioned differently in the mice fed with chow diet or HFHS diet.We hypothesize Sirt 6 deficiency causes coronary endothelial dysfunction and contributes to CMD; activating Sirt6 will ameliorate CMD. EDD was assessed using myography (DMT). Myocardial blood flow (MBF) was measured by Doppler. Our preliminary data show that the mediator of coronary vasodilation switched from NO to H2O2in the Sirt6 knockout mice with impaired EDD. Interestingly, when the mice fed on HFHS were treated with Sirt 6 activator MDL-800, the coronary microvascular function was improved, and the blood glucose level was decreased. The underlying mechanism and the pathways involved will be elucidated.

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Novembre 2024

Abstract 4140185: The Burden Of Substance Abuse And Mental Health Disorders In Patients Admitted With Stress Cardiomyopathy

Circulation, Volume 150, Issue Suppl_1, Page A4140185-A4140185, November 12, 2024. Introduction:Several studies have linked mental health disorders and substance abuse as risk factors for stress cardiomyopathy (SC). However, the true burden of these disorders amongst patients with stress cardiomyopathy remains unknown.Methods:We used the 2016-2020 National Inpatient Sample database to identify hospitalizations for SC who underwent diagnostic catheterization. We assessed the proportion of patients diagnosed with a substance abuse or mental health disorder. Subsequently, the association of these disorders in SC compared to patients admitted for myocardial infarction (MI) was assessed using the chi-square test.Results:From 2016 to 2020, there were 33,075 hospitalizations for stress cardiomyopathy who were diagnosed by cardiac catheterization. Of these patients, 5,920 (17.9 %) had depression, 8,500 (25.7 %) had anxiety, 1058 (3.2 %) had severe stress reactions, and 16,372 (49.5 %) were diagnosed with a mental health disorder. 9,955 (30.1 %) were smokers, 5,358 (16.2%) abused hallucinogens, 5,457 (16.5 %) abused cocaine, 5,457 (16.5%) abused sedatives, 6,019 (18.2 %) abused cannabis, 5,920 (17.9%) abused opioids, 6,416 (19.4 %) abused alcohol. Subsequently, the association of stress cardiomyopathy with mental and substance abuse disorder was compared with patients admitted with myocardial infarction See Table 1.Conclusion:Mental health and substance abuse disorders are common in patients diagnosed with SC. These disorders are more commonly present in SC compared to MI. Further research is needed to assess the significance of these findings.

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Novembre 2024

Abstract 4140181: Mechanisms of SGLT-2 Inhibitor Empagliflozin in Attenuating Intramitochondrial Stress and Restoring Mitochondrial Function in Hyperglycemic Cardiomyocyte

Circulation, Volume 150, Issue Suppl_1, Page A4140181-A4140181, November 12, 2024. Systemic hyperglycemia causes tissue damage and triggers cardiovascular disease (CVD). Sodium-glucose cotransporter-2 inhibitors (SGLT-2i) are a novel class of glucose-lowering agents that have shown unexpected benefits in clinical trials for the treatment of CVDs. We aim to investigate the underlying mechanisms of how SGLT-2 inhibitors alleviate CVDs associated with elevated glucose stress. iPSC-derived cardiomyocytes (iPSC-CM) were incubated with high glucose concentrations for 72 hours. Mitochondrial function in these cardiomyocytes was assessed by flow cytometry with JC-1 staining and ATP luminescence assay. Intracellular reactive oxygen species (ROS) and intramitochondrial calcium stress were measured using CellROX, MitoSOX, and Rhod-2 AM staining. Patch clamp was employed to determine ion current changes in the cardiomyocytes. Mitochondrial oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were determined using the Seahorse XFe96 analyzer. In addition, qPCR, Western blot, and DM mouse heart histological analysis were performed to assess the regulation of associated molecules. The results indicated that exposure to a high glucose environment caused cardiomyocyte injury and impaired mitochondrial biosynthesis. Empagliflozin exhibited a beneficial effect on mitochondrial function by reducing ROS production and calcium deposition. It also mitigated the reduction in respiratory OCR of cardiomyocytes induced by high glucose incubation. Furthermore, molecular analysis revealed that Empagliflozin attenuated the dysregulation of mitochondrial calcium channels and biosynthesis by reducing associated gene expression, includingBcl2,Mfn1,Mx2,Oas1,Ant3,Mcu,Micu1,Vdac1,Ryr2, andCypd-ppid. Histological analysis of DM mouse hearts demonstrated that reduced MFN2 and ZBP1 were target molecules for hyperglycemia-induced reduction of calcium channel currents in cardiomyocytes and could be restored by Empagliflozin treatment. This study concludes that high glucose stress diminishes mitochondrial calcium channel regulators MFN2 and ZBP1 in cardiomyocyte, which reduces calcium channel currents and leads to sensitization of cardiomyocyte to arrhythmogenesis, resulting in VT/VF. It provides experimental evidence for the clinical efficacy of Empagliflozin in ameliorating CVDs and managing diabetes-related CVDs.

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Novembre 2024

Abstract 4143303: Association of Preeclampsia with Long-Term Coronary Microvascular Dysfunction Utilizing Cardiac Stress Magnetic Resonance Imaging

Circulation, Volume 150, Issue Suppl_1, Page A4143303-A4143303, November 12, 2024. Introduction:Preeclampsia is a hypertensive disorder of pregnancy associated with cardiovascular disease. Systemic peripartum microvascular alternations have been implicated in pregnancies complicated by preeclampsia. Whether coronary microvascular dysfunction is a potential mediator of preeclampsia-associated cardiovascular risk is unknown. We aimed to determine whether individuals with a history of preeclampsia have coronary microvascular dysfunction measured by cardiac magnetic resonance imaging (CMR) at least 5 years postpartum.Methods:Women with singleton pregnancies complicated by preeclampsia and a comparator group with uncomplicated, normotensive deliveries were identified and prospectively enrolled to undergo regadenoson stress perfusion CMR (1.5T Signa Artist GE HealthCare) at least 5 years postpartum. Using the dual sequence technique, fully quantitative perfusion values were determined using Fermi deconvolution. Myocardial perfusion reserve (MPR) was calculated as the ratio of stress to rest myocardial blood flow (MBF).Results:Twenty-three subjects (41.0 ± 6 years, 12.7 ± 5 years post-partum) were included. Women with a history of preeclampsia (n=11) were compared to a control group of women with prior normotensive pregnancy (n=12) (Figure 1A). Obesity and diabetes were more common with preeclampsia, but there was no significant difference in the presence of hypertension between the groups (Table 1A). There was no difference in stress MBF. However, preeclampsia was associated with higher rest MBF (1.47 ± 0.54 mL/g/min vs. 1.19 ± 0.29 mL/g/min; p=0.07) and MPR (1.96 ± 0.46 vs 2.66 ± 1.0; p=0.02) compared to normotensive pregnancy (Figure 1). Similarly, corrected MPR remained significantly lower with prior preeclampsia versus uncomplicated pregnancy (2.36 ± 1.0 vs 3.36 ± 1.46; p=0.03).Conclusions:In this study, we observed significantly reduced coronary microvascular function following a pregnancy complicated by preeclampsia at least 5 years postpartum. Heightened cardiovascular risk factors may attenuate this association; however, these observations indicate that systemic microvascular dysfunction in preeclampsia also involves the coronary microcirculation. Further research is needed to better understand the timing and association of these microvascular changes concerning preeclampsia and later heart disease.

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Novembre 2024

Abstract 4148019: Shear Stress Affects Human Aortic Endothelial Heparan Sulfate Expression Response to Inflammatory Stimulus

Circulation, Volume 150, Issue Suppl_1, Page A4148019-A4148019, November 12, 2024. Background:Heparan sulfate (HS) proteoglycans act as mechanosensors on endothelial cells (ECs), regulating EC morphology and function. HS expression is affected by culture under static or dynamic conditions. HS response to inflammatory stimulus under both conditions is not well characterized. This study investigated HS expression on human aortic ECs (HAECs) under static and arterial flow conditions.Hypothesis:Inflammation modeled by TNFa significantly decreases HS epitope on HAECs under both static and arterial flow conditions.Aims:To establish the effect of TNFa on HS expression in HAECs.Methods:Passages 4 through 8 HAECs (ATCC) were cultured to confluence in endothelial growth medium (Vasculife) in Ibitreat µ-Slide 8 well high chambered coverslip slides or Ibitreat µ-Slide VI 0.4 flow channel slides. Cells were treated with TNFa at 100 ng/mL for 3 hours under static conditions or conditioned with 10 dyn/ cm2 of shear stress for 24 hours and then treated with TNFa at the same concentration added to the circulating media for 3 hours. HAECs were fixed in 2% paraformaldehyde/ 0.1% glutaraldehyde for 30 minutes followed by blocking with 2% goat serum for 30 minutes, both at room temperature. Primary antibody to the 10E4 HS epitope was incubated at 4°C overnight (1:100; 10E4 epitope, AMS Biotechnology, USA) followed by incubation in Alexa Fluor 488 goat anti-mouse secondary antibody (1:300, Molecular Probes, USA) for 1 hour at room temperature. HAECs nuclei were stained using 4′,6-diamidino-2-phenylindole and immersed in phosphate buffered saline for confocal imaging using a laser scanning microscope (Zeiss, LSM 880, 20X).Results:TNFa significantly (p < 0.05) increased HS expression in HAEC monolayers treated under static conditions compared to untreated control and heparinase III treated HAECs (Figure 1A). HAEC monolayers conditioned under arterial shear stress expressed significantly (p < 0.05, ANOVA with Tukey’s post-hoc) higher HS levels compared to baseline static controls; however, flow conditioned HAECs did not show any difference in HS expression under untreated compared to TNFa conditions (Figure 1B).Conclusion:These data indicate that fluid shear stress may program endothelial cells to significantly alter their HS expression and response to inflammatory stimuli.

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Novembre 2024

Abstract 4145408: The Unexpected Heart Stopper: A Case of Ketamine-Induced Stress Cardiomyopathy Requiring Mechanical Circulatory Support

Circulation, Volume 150, Issue Suppl_1, Page A4145408-A4145408, November 12, 2024. Background:Stress cardiomyopathy (SCM) is rarely triggered by ketamine and seldom leads to cardiogenic shock. Ketamine-induced catecholaminergic surge can lead to myocardial stunning with transient ischemia and subsequent reversible heart failure. Mechanical circulatory support can be successfully leveraged in SCM-associated cardiogenic shock while awaiting myocardial recovery.Case Presentation:A 28-year-old female with chronic pain was admitted for failure to thrive secondary to opioid-induced gastroparesis. The patient was weaned off opiates while on ketamine over 4 days. After halting ketamine, the patient had a cardiac arrest with eventual return of spontaneous circulation. After being extubated, she developed chest pain, hypotension, and ventricular tachycardia with anterolateral ST elevations, troponin leak, and lactic acidosis. TTE revealed an EF

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Novembre 2024

Abstract 4145148: The Hypertrophic Cardiomyopathy Associated Junctophilin-2 E169K Variant Disrupts Mitofusin-2 Binding and Elicits a Pathological Cellular Response to Metabolic Stress

Circulation, Volume 150, Issue Suppl_1, Page A4145148-A4145148, November 12, 2024. Introduction:Junctophilin-2 (JPH2) plays essential roles in multiple cardiac processes including calcium handling, t-tubule structure, and gene regulation. We recently showed JPH2 also has a mitochondrial role as it binds the mitochondrial protein mitofusin-2 (MFN2) and modulates mitochondrial metabolic function. However, the impacts of JPH2 disease-causing variants on MFN2 binding and subsequent cellular responses to metabolic stressors are unknown.Methods:Disease-associated variants in the MFN2 binding domain of JPH2 were engineered and recombinantly expressed in E. coli cells. Purified proteins were then subjected to pulldown experiments to assess MFN2 protein binding. Alphafold3 modeled how MFN2 and JPH2 and JPH2 E169K mutants interacted in the presence or absence of fatty acids. Wildtype JPH2 or JPH2 E169K expression was directed by a doxycycline inducible promoter after being cloned into the AAVS1 locus in JPH2 knockout iPSC-cardiomyocytes. In vitro metabolic stress was induced by incubating iPSC-CM with 150 μM oleate, 150 μM palmitate, and 500 μM carnitine overnight. Super resolution confocal microscopy visualized mitochondria integrity, nuclei shape and size, and lipid droplet accumulation and morphology.Results:In pulldown experiments, the JPH2 E169K mutation disrupted MFN2 binding. Alphafold3-based modeling showed JPH2 E169K disrupted the interaction between the two proteins when modeled with or without lipids (A-D). Control, wild type JPH2, and JPH2 E169K iPSC-CM displayed divergent responses to in vitro metabolic stress. JPH2 E169K cells exhibited pathological mitochondrial network changes characterized by a lower mitochondrial footprint and less network branches (E-G). In addition, the JPH2 E169K iPSC-CM accumulated significantly more lipid droplets in the cytoplasm and the nucleus, and the JPH2 E169K lipid droplets were significantly larger than the other cell types (H-K). Finally, the accumulation of lipid droplets impacted nuclear morphology as the JPH2 E169K cells had nuclear hypertrophy and nuclei were more ellipse-shaped (L-N).Conclusion:The JPH2 E169K variant disrupts MFN2 binding, which results in heightened metabolic stress characterized by lipid droplet accumulation and mitochondrial and nuclear morphological changes. These results implicate a new pathophysiological mechanism for how the JPH2 E169K mutation causes cardiac dysfunction.

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Novembre 2024