bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract 18802: Endothelial-Mesenchymal Transition (EndMT) of the Atrial Endocardial Endothelial Layer: A Potential Contributor to Atrial Pathological Remodeling?
Authors: Greener Ian D , Rutledge Cody A , Dudley Samuel C
Published: April 2024

Introduction:
Atrial fibrosis is a major contributor to the atrial fibrillation substrate but the mechanisms underlying its formation remain poorly understood. One major molecule implicated in enhanced fibrosis in response to atrial stress is Angiotensin II. EndMT describes the process of endothelial cell (EC) transformation into a myofibroblast - the major extracellular matrix synthesizing cell.

Methods & Results:
Atria of 4-6 week old angiotensin converting enzyme overexpressing mice (ACE88) were compared to ACE wild-types (WT). qPCR demonstrated significantly increased Col1A2 (11.5+/-0.7vs2.7+/-0.7; p=7.3E-6) and FN1 (2.7+/-0.1vs0.86+/-0.16 ; p=7.3E-6) transcripts in ACE88 compared to WT. Interestingly, collagen I & CD31 immunolabeling revealed a more complex transmural fibrotic pattern: intra-atrial collagen I was increased as expected, but a strong increase in collagen I intensity was also detected in the endothelial layer enveloping atrial fascicles and lining the endocardial free wall. CD31 immunolabeling of ACE88 atria revealed a “rugged” lining of atria endocardial free-walls & fascicles compared to the finely demarcated WT counterparts. Significantly increased intra-atrial uptake of Evan’s Blue dye in ACE88 vs WT (0.15+/-0.01vs 0.04+/-0.006; p=<0.002) confirmed a disruption of endothelial barrier function. In addition, atria of 16-week old mice with myocardial infarction (MI) were studied at 2 & 4 weeks postMI. Similar to ACE88 mice, mRNAs for Col1A2 (0.91+/-0.1vs1.5+/-0.2 ; p=0.06) and FN1 (0.9+/-0.2vs1.3+/-0.1; p=0.052) showed a strong tendency for upregulation 4 weeks post-MI compared to aged-matched c57 atria (c57). Surprisingly, strongest collagen I post-MI labeling localized in proximity to CD31 labeling at 2 weeks, with little change in intra-atrial collagen I content. Significantly increased collagen I intensity was detected in the endocardial EC layer 4 weeks post-MI compared to c57 (31+/- 3vs45+/-3; p=0.009).

Conclusions:
These data suggest the endocardial EC layer may be an early sensor to increased atrial stress; endocardial EndMT may be an early event during the atrial remodeling process and perhaps contributes to global intra-atrial remodeling through altered paracrine and/or permeability mechanisms.
Abstract 18808: Relationship Between Myocardial Extracellular Volume and Myocardial Scar in Non-ischemic Cardiomyopathy Patients
Authors: Ghosn Mohamad G , Chaikriangkrai Kongkiat , Shah Dipan J
Published: April 2024

Background:
Delayed Enhancement (DE) Cardiovascular magnetic resonance (CMR) has been established as the reference standard for assessment of myocardial replacement fibrosis (RF) in ischemic heart disease. However DE-CMR is unable to identify diffuse interstitial fibrosis (IF). Recently, T1 mapping of the myocardium following the administration of gadolinium contrast has been shown to identify increased extracellular volume (ECV) which occurs in the setting of IF. For this study we sought to evaluate the relationship between RF and IF in patients with nonischemic cardiomyopathy (NICMP).

Method:
We enrolled 80 consecutive patients with NICMP who underwent DE-CMR and T1 mapping using a modified look-locker inversion recovery (MOLLI) technique. The extent of RF was determined by analysis of DE-CMR images. The ECV was estimated from the concentration of extracellular contrast agent in the myocardium relative to the blood in the dynamic steady state. Care was taken to avoid measuring ECV in regions with RF detected on DE-CMR.

Results:
The cohort consisted of 61.3% of patients with RF. In RF group, the mean scar burden was 7.4±9.9% of left ventricle myocardium. Patients with RF had higher ECV compared to those without RF (36.1±10.7 and 31.9±6.7 respectively; p=0.04). The left ventricular ejection fraction (LVEF) and stroke volume (SV) were significantly lower in patients with increased ECV (p<0.005). Same relation held true for patients with RF (p<0.005). There was a significant increase in ECV for patients with RF of more than 5% of LV myocardium (p<0.001). In linear regression analysis, ECV is positively associated with scar burden (Beta weight=0.527, p<0.001).

Conclusion:
This study suggests that LVEF and SV are significantly lower in patients with increased ECV and for those with RF. There is a positive relationship between increased ECV and RF in patients with NICMP. There appears to be a threshold effect where the largest increase in IF occurs when there is more than 5% RF.
Abstract 18851: Cardiovascular Disease: The Leading Cause of Pregnancy-Related Death in California 2002-2005
Authors: hameed afshan B , Foster Elyse , McCain Christy , Morton Christine , Main Elliott
Published: April 2024

Introduction:
The California Pregnancy-Associated Mortality Review (CA-PAMR) was started in 2006 by the California Department of Health, Maternal, Child, and Adolescent Health Division in response to rising rates of maternal mortality with the goal of understanding and reducing maternal morbidity and mortality.

Methodology:
CA-PAMR uses an enhanced surveillance methodology to identify and investigate maternal deaths, as described previously. An expert committee reviewed medical records to determine pregnancy-related deaths, their clinical causes, contributing factors and opportunities for quality improvement.

Results:
From 2002-2005, there were 2,147,492 live births and 732 women died while pregnant or within 1 year of pregnancy. Among them, 207 were determined to be pregnancy-related: 53 were from cardiovascular disease (CVD) and two-thirds (n=33) of those from cardiomyopathy (CMP).

Compared to women who died from non-cardiac causes, women who died from any CVD were twice as likely to be African-American (39% vs. 17%, p<.01) and obese (BMI>30) (42% vs. 26%, p<.05), and had documented substance abuse during pregnancy (27% vs. 10%, p<.01) and to die ≥ 42 days postpartum (31% vs. 6%, p<.01). Almost a quarter (22%) of CVD deaths had a concomitant diagnosis of hypertension or preeclampsia.

Similarly, the CMP deaths were three times as likely to be African-American (46% vs. 18%, p<.01), twice as likely to be obese (47% vs 27%, p<.05), four times as likely with substance abuse (37% vs. 9%, p<.01), and to die ≥ 42 days postpartum (46% vs. 5%, p<.01). Concomitant diagnosis of hypertension or preeclampsia occurred in 30% of CMP deaths.

Overall, for those diagnosed before death (n=29), the mean time from symptom onset to diagnosis was 26 days (range=0, 223 days) and from diagnosis to death was 79 days (range 0, 347 days). Patient and health care provider factors were identified as having contributed to 86% and 71% of the deaths respectively, and 30% of the CVD deaths were considered potentially preventable.

Conclusion:
Medical expert review of maternal deaths has provided additional insight into CVD deaths that occur during or after pregnancy. Earlier recognition and referral of a symptomatic patient by obstetric providers may help prevent serious morbidity and mortality.
Abstract 18855: Global Longitudinal Strain is Reduced in Congenital Aortic Stenosis and Associated With Focal Myocardial Fibrosis
Authors: Dusenbery Susan M , Lunze Fatima I , Jerosch-Herold Michael , Geva Tal , Newburger Jane W , Colan Steven D , Powell Andrew J
Published: April 2024

Background:
In congenital aortic stenosis (AS), therapy to relieve obstruction is directed toward preserving myocardial function and structure, but the optimal timing remains controversial. Myocardial strain measurements of regional systolic function may be more sensitive than conventional measures, such as ejection fraction (EF), and thus serve to refine the indications for intervention. We hypothesized that congenital AS pts with normal EF have impaired LV strain associated with myocardial fibrosis.

Methods:
Inclusion criteria for cases were congenital AS with a peak Doppler gradient ≥20 mm Hg at any time, age<30 yo, extracellular volume fraction (ECV) and late gadolinium enhancement (LGE) assessed by cardiac MR (CMR), LV EF >54%, and a concurrent echocardiogram. Strain measures were compared to normal controls of similar age (n=15, median age 15). Speckle tracking echocardiographic strain was used to measure peak global longitudinal, circumferential, and radial strain. The ECV, a measure of diffuse fibrosis, was calculated with a Look-Locker technique. LGE was used to assess focal fibrosis, and classified as present or absent.

Results:
Twenty-nine pts met inclusion criteria with a median age of 16 yrs (1.7-25), peak AS gradient of 48 mm Hg (0-90), aortic regurgitation fraction by CMR of 25% (0-60), LV EF 65% (55-79), and mean ECV 0.27 (0.22-0.38). Global longitudinal strain was significantly lower in AS patients than controls (-17.0 ± 3.0% vs. -20.9 ± 2.4%, p<0.001). Global circumferential strain (-26.7 ± 5.6% vs. -25.9 ± 3.6%, p=0.72) and global radial strain (29.6 ± 7.7% vs. 34.2 ± 8.8%, p=0.063) were not significantly different. Reduced global longitudinal strain was associated with LGE (p=0.036) but not ECV (p=0.14) Global longitudinal strain was not associated with peak echo AS gradient prior to CMR, LV mass/volume ratio, or a history of any aortic valve intervention.

Conclusions:
In this cohort of children and young adults with congenital AS and preserved EF, global longitudinal strain was lower than in controls and associated with focal fibrosis but not diffuse fibrosis. Further studies are warranted to determine whether strain measurements should be used to determine the timing for intervention in AS to better preserve myocardial structure.
Abstract 18881: Improper Elastic Fiber Assembly Drives Cardiac Pathology
Authors: van Deel Elza D , te Riet Luuk , Moltzer Els , van Vliet Nicole , Fiedler Lorna , Boontje Nicky , Rouwet Ellen , van der Velden Jolanda , Schneider Michael D , Duncker Dirk J , Essers Jeroen
Published: April 2024

Elastin is ubiquitously expressed in the cardiovascular system and essential for maintaining aortic wall integrity and function. Little is known however, about the role of elastin in the heart. To explore the influence of elastin on cardiac pathology we knocked down an essential protein for elastogenesis, fibulin-4, in human induced pluripotent stemcell (iPS)-derived cardiomyocytes. Strikingly, 90% reduction of fibulin-4 expression by shRNA, increased cardiomyocyte size by 35% and enhanced expression of atrial natriuretic peptide (ANP) and of TGFβ-regulated genes such as connective tissue growth factor and plasminogen activator inhibitor-1 in these cultured cardiomyocytes (all p<0.05). Accordingly, mice with a 75% reduction in fibulin-4 expression (Fibulin-4R/R), developed cardiac hypertrophy, dilation and dysfunction (ejection fraction [76±2 to 21±3 %]) as well as aortic aneurysms. This was accompanied by elevated myocardial TGFβ signalling and ANP, while expression of sarcoplasmic reticulum calcium transport ATPase and maximal force generating capacity of single membrane-permeabilized cardiomyocytes was reduced by 60% and 25%, respectively (both p<0.05). Subsequently, we explored the influence of fibulin-4 and elastogenesis on the development of cardiac pathology by subjecting mice with a 50% reduction in fibulin-4 expression (Fibulin-4+/R), without apparent cardiovascular abnormalities, to 4 weeks of transverse aortic constriction (TAC). Following TAC, mortality was markedly increased in Fibulin-4+/R animals compared to wildtype mice [20% to 84%; p<0.05]. Moreover, in surviving mice, reduced fibulin-4 expression aggravated TAC-induced LV systolic and diastolic dysfunction and pulmonary congestion without affecting valvular function. In conclusion, using gradually reductions in fibulin-4 expression in mice and iPS derived cardiomyocytes we show that improper elastic fiber assembly drives cardiac pathology.
Abstract 18895: Freedom From Recurrent Ventricular Tachycardia After Ablation is Associated With Improved All-Cause Mortality
Authors: Tung Roderick , Yu Ricky , Vaseghi Marmar , Buch Eric , Bradfield Jason , Mandapati Ravi , Boyle Noel , Shivkumar Kalyanam
Published: April 2024

Introduction:
ICD therapy and recurrent VT have been shown to increase the risk for mortality. Catheter ablation of ventricular tachycardia has been demonstrated to reduce recurrent episodes of VT but no studies to date have demonstrated a reduction in all-cause mortality.

Methods:
Retrospective analysis of all patients referred for ablation of scar-mediated VT from 2004-2011 were reviewed. Acute procedural success and 1 year-freedom from VT recurrence were correlated with all-cause mortality at 1 year. Separate analyses were performed for patients with ICM and NICM and stratified by EF <30%.

Results:
A total of 127 patients were included: 63±11 yrs, male 86%, ICM 56% (EF 28±12), NICM 44% (EF 31±15). Antiarrhythmic usage was 87%. Acute procedural success of noninducibility was achieved in 51% of patients with ICM and 38% with NICM. Acute procedural success predicted freedom from mortality for the NICM group (95% vs 67%, p=0.02), but not for the ICM group (76% vs 65%, p=0.43). Freedom from recurrent VT within the 1 year follow-up period was associated with a reduction in all-cause mortality for patients (ICM 82% vs 48%, p=0.005; NICM 100% vs 61%, p=0.006). However, the mean EF was significantly higher in patients who survived at 1 year (ICM 30±12 vs 23±8 ICM, p=0.007; NICM 33±15 vs 22±6, p<0.001). When stratifying patients with EF≤30%, freedom from VT remained a predictor of 1 year survival (ICM 74% vs 42%, p=0.04; NICM 100% vs 50%, p=0.005).

Conclusion:
Freedom from VT at 1 year is associated with a reduction in all-cause mortality in patients with ICM and NICM who underwent catheter ablation of VT. EF is also a significant predictor of all-cause mortality, although the association between recurrent VT and mortality remains for when patients with EF<30% are analyzed.
Abstract 189: The Effects of Fw-ii Axial Blood Pump on Cardiogenic Shock After Acute Myocardial Infarction in a Sheep Model
Authors: Chen Haibo , Zhou Jianye , Sun Hansong , Tang Yue , Liu Guangmao , Zhang Yan , Hu Shengshou , Hu Shengshou
Published: April 2024

Background:
High-risk percutaneous coronary interventions (PCI), refractory cardiogenic shock and in-lab cardiac arrest are all associated with a high mortality rate in patients with acute myocardial infarction (AMI). The extent to which the use of FW-II axial pump can improve outcomes in cardiogenic shock is not known.

Methods:
In 12 adult male sheep, cardiogenic shock was induced by circumflex coronary artery ligation for 90 min, followed by 240 min of reperfusion. The animals were divided into two groups: control group had non-mechanic supportive care including dopamine, dobutamine and other drugs; FW-II axial pump group was supported with FW-II axial pump from 90 min after ischemia to 240 min after reperfusion. Hemodynamic efficacy (mean arterial pressure (MAP), cardiac index (CI), pulmonary artery pressure (PAP) and systemic vascular resistance (SVR)), left ventricular systolic / diastolic diameter, carotid artery blood flow velocity were measured at 3 specific conditions: preligation, postligation and before being euthanasiaed. Reperfusion area was detected by Evans blue, and apoptosis detection included TUNEL staining, caspase-3 activity, bax and bcl-2 relative expression in normal, borderline and infarcted myocardium.

Results:
Animals in control group survived for an average of 24 ± 9.6 hours, and Animals in FW-II group survived 72 hours and were euthanasiaed. Compared with control group, MAP, CI, artery diastolic velocity, and oxygen delivery index (DO2I and VO2I) were significantly higher (P <0.05) in FW-II pump group; PAP and SVR was significantly lower than the control group (P <0.01); Infarct ratio (percentage of the infarct area relative to the area at infarct risk) was significantly reduced in FW-II pump group with a significant difference from control group (P < 0.001). Apoptotic index and bax expression of border zone myocardium were significantly lower in FW-II pump group (P<0.01). However, there were no difference between control group and FW-II pump group for apoptotic index and bax expression in normal and infarcted myocardium (P >0.05).

Conclusion:
Short-term assistance of FW-II axial pump improved the survival of cardiogenic shock by increasing systemic organ perfusion and reducing myocardial apoptosis.
Abstract 18900: Impact of Acute and Chronic 5-Hour Energy Drink Consumption on Electrocardiographic Parameters
Authors: Shah Sachin A , Lacey Carolyn , Potts Vicki , Lopez Christopher M , Riddock Ian , Lee Michael , Milazzo Nicholas , Dargush Anthony E
Published: April 2024

INTRODUCTION:
The impact of energy drinks on the cardiac rhythm remains unknown. QT/QTc prolongation has been known to induce life threatening arrhythmias. We sought to determine the impact of 5-Hour Energy shot on the QTc interval after acute and chronic consumption.

Methods:
This was a randomized, placebo controlled, crossover study enrolling young healthy volunteers not on any medications. Subjects received the study drink (5 Hour Energy shot or placebo) twice daily separated by approximately 7 hours for the first 7 days. This was followed by a washout period of 6 days and the alternate study drink was consumed for the final 7 days. A 12-lead electrocardiogram was performed at baseline, 1, 3 and 5 hours on days 1, 7, 15 and 21. Automated ECG measurements were used for per-treatment and ITT analysis and analyzed using the paired student’s t-test.

Results:
A total of 24 subjects (29±5.8 years) were included for analysis. QTc values after consumption of a single placebo-dose were 414±18, 413±15, 413±19 and 417±19 milliseconds at baseline, 1, 3 and 5 hours respectively. Post consumption of a single 5 Hour Energy dose, QTc values were 415±17, 408±19, 410±20, and 413±17 milliseconds at baseline, 1, 3 and 5 hours, respectively (all time matched inter- group p-values >0.291). QTc values after consumption of placebo for 7 days were 415±20, 413±18, 409±19, and 413±22 milliseconds at baseline, 1, 3 and 5 hours, respectively. Post consumption of 5 Hour Energy shots for 7 days, resulted in QTc values of 415±22, 413±24, 415±24, and 415±21 milliseconds at baseline, 1, 3 and 5 hours, respectively (all time matched inter- group p-values >0.197 ). There was no difference between the PR interval, QRS duration, QT interval and heart rate between the two groups.

CONCLUSION:
5-Hour Energy did not induce any significant changes in the QTc interval or other ECG parameters after single and multiple doses throughout a 7 day period. These results may vary between different energy drinks due to the varying ingredients within them. DISCLOSURE: The views expressed in this material are those of the authors and do not reflect the official policy or position of the U.S. government, the Department of Defense, or the Department of the Air Force.
Abstract 18953: Prevalence of and Risk Factors for Radial Artery Complications After Transradial Cardiac Catheterization
Authors: Ruhnau Johannes , Schröder Stephen
Published: April 2024

Background:
In recent years, radial access for cardiac catheterization gains popularity. One of the most common complications is radial artery occlusion (RAO). There are various numbers for the prevalence of RAO in literature, ranging from 5 to 30% when using a 6F sheath.

Our study was designed to investigate the prevalence of radial artery (RA) complications (RAO, false aneurysm, arteriovenous fistula) in a single center population using a 6F sheath.

Methods:
415 patients* (pts) were examined clinically and with duplex sonography 4 - 68 weeks after cardiac catheterization (60.7% (n=254) male, median age 68 y (33 - 88).

In n=103 pts (24.6%) an intervention had been performed immediately after the diagnostics.

Results:
Patient characteristics are summarized in table 1. RAO was found in 15/418 cases (3.6%, n = 10 female, n = 5 male). Of those 10 patients, 3 showed (transient) symptoms (dysaesthesia, feeling of heaviness of the hand), cases of critical ischaemia were not found.

No false aneurysm was found, one pt showed an arteriovenous fistula in the proximal RA. One patient showed significant stenosis of the middle portion of the brachial artery in addition to RAO, another one showed a mild stenosis of the RA.

Women showed a significantly higher rate of RAO (n = 10, 66.7% in the RAO group vs. n = 154, 40.3% in the comparison group, p = 0.03). Other risk factors seem to be diabetes (n = 6, 40% vs. n = 106, 26%) and renal insufficiency (n = 3, 20% vs. n = 43, 11%), although the risk was not significantly increased. Interestingly, a coronary intervention does not seem to increase the risk of RAO (n = 2, 13% vs. n = 101, 26%).

Hypertension, dyslipidemia, present or past smoking, body height, age, and BMI did not have significant influence.

Conclusion:
Vascular complications, especially RAO, after radial access for cardiac catheterization are quite rare and remain usually asymptomatic. Women are at higher risk. Diabetic pts and pts with impaired renal function seem to be at slightly higher risk.
Abstract 18954: Novel Role of De Novo Matricellular Protein Cyr61 in Bridging Lysophosphatidic Acid and Integrin Pathways Leading to Smooth Muscle Cell Migration
Authors: Cui Mei-Zhen , Zhang Fuqiang , Wu Daniel D , Hao Feng , Xu Xuemin
Published: April 2024

Lysophosphatidic acid (LPA), a potent bioactive lipid, markedly induces smooth muscle cell (SMC) migration, which is one of the important processes involved in atherosclerotic lesion development. In order to search for key molecules that control LPA-induced SMC migration, we performed gene microarray analysis and attempted to identify LPA-induced extracellular molecules responsible for LPA-triggered cell migration. We observed that LPA selectively induced the expression of the matricellular protein Cyr61, a multifunctional matrix-related protein, which has been implicated in cell angiogenesis, proliferation, adhesion and migration. We hypothesize that Cyr61 mediates LPA-induced cell migration. Our data show that LPA induces temporal and spatial expression of Cyr61 protein in SMCs. LPA-induced de novo Cyr61 proteins promptly accumulate in the Golgi apparatus and then translocate to the extracellular matrix. Cyr61 specific siRNAs diminishes LPA-induced cell migration, indicating the novel regulatory role of the induced matricellular protein Cyr61 in LPA-induced cell migration. Using primary SMCs derived from LPA receptor 1 (LPA1) knockout and LPA2 knockout mice, our data reveal that LPA1 is required for LPA-induced Cyr61 expression in SMCs and cell migration. Furthermore, LPA induces profound activation of focal adhesion kinase (FAK) in SMCs in later time points, coinciding with the accumulation of Cyr61in the extracellular matrix. FAK is an intracellular kinase important in regulating cell migration. Our data demonstrated that knockdown of de novo Cyr61 expression blocked LPA-induced cellular FAK activation and cell migration. Integrin alpha6 and beta1 have been reported to interact with Cyr61 in SMCs. We found that knockdown of the expression of integrin alpha6 or beta1 prevented LPA-induced FAK activation and cell migration. Taken together, these data reveal that a novel LPA/Cyr61 pathway controls cell migration and that de novo Cyr61 in extracellular matrix bridges LPA and integrin signaling, which in turn, activates FAK leading to cell migration. Understanding this novel pathway will provide new insights into mechanisms underlying the development of cell migration related disorders including atherosclerosis and restenosis.
Abstract 18985: Lentil-Based Diets Reduce Vascular Remodeling Through a p38 Mitogen-Activated Protein Kinase Dependant Mechanism in the Spontaneously Hypertensive Rat
Authors: Hanson Matthew , Zahradka Peter , Anderson Hope , Taylor Carla
Published: April 2024

Hypertension is a major driving force behind arterial remodeling, which increases stiffness, and decreases compliance and function. Certain pharmaceuticals are capable of lowering high blood pressure, but most interventions are unable to also reverse remodeling. We have found that lentils are able to significantly attenuate the development of hypertension in the SHR, however the mechanism for this action remains unresolved. The current study examined the hypothesis that the positive actions of lentils on blood pressure are mediated through direct changes in arterial function that decrease remodeling and improve arterial compliance. Seventeen-week SHR were randomly assigned to groups (n=8/group) fed (i) 30% w/w green lentils, (ii) 30% w/w red lentils, (iii) 30% w/w mixed lentils (red and green), or (iv) no lentils. Normotensive WKY control rats were fed either mixed lentil or no lentil diets (n=8/group). BP and pulse wave velocity were measured weekly; pressure myography was performed at termination. Western Blotting was performed on aorta protein samples. There were no dietary related changes in pulse wave velocity, however, green lentils restored arterial compliance to a level better than control-fed WKY. All lentil fed animals exhibited arterial stiffness comparable to WKY control, with green lentils experiencing the largest improvement according to myography measurements. All lentils reduced the media:lumen ratio to a level between control fed SHR and WKY. Western blotting indicated a decrease in p38 MAPK activation in lentil-fed SHR with no change in ERK1/2 phosphorylation. Although both ERK1/2 and p38 MAPK are potent mediators of vascular remodeling, only p38MAPK phosphorylation is redox sensitive. These data would indicate that lentil-based diets are able to decrease vascular remodeling by ameliorating p38 MAPK-dependent redox-sensitive signaling cascades.
Abstract 18994: Shear-Dependent Membrane Scrambling and Microvesiculation and an Important Role for Rac1
Authors: Delaney Michael K , Liu Junling , Zheng Yi , Du Xiaoping
Published: April 2024

Surface exposure of phosphatidylserine (PS) and the release of membrane microvesicles (microparticles) are critically important for blood platelets and leukocytes to promote coagulation and inflammation during vascular injury. The caspase-dependent apoptotic signaling pathway and high intracellular calcium-dependent mechanisms have been implicated in the induction of these events under static conditions. However, it is known that when stimulated with physiological agonists under static conditions only a small percentage of platelets actually respond in a procoagulant manner. Thus, these mechanisms do not fully explain the potent procoagulant response of platelets to physiological stimuli. Here we demonstrate a novel shear stress-dependent mechanism of PS exposure and microvesiculation in platelets stimulated by physiological agonists. We show that exposing agonist-stimulated mouse and human platelets to increasing levels of shear led to greatly increased levels of surfaced exposed PS, shedding of membrane microvesicles, and in particular an increased sensitivity of platelets to display procoagulant activity at low concentrations of physiological agonists. Thus, shear stress is critical for inducing the surface exposure of PS and the shedding of PS-exposed microvesicles in platelets. Moreover, using the Rac1 inhibitor
NSC23766
and platelet-specific Rac1
-/-
platelets we identified Rac1, a member of the Rho family small GTPases, as being a critical mediator of the platelet procoagulant response to shear. We also show that Rac1 regulates this shear-induced response independent of the known apoptosis signaling pathway, as Rac1
-/-
platelets showed no difference in the caspase-dependent pathway of PS exposure induced by ABT737. Importantly, the role of Rac1 in mediating shear-dependent PS exposure and microvesicle release appears to be independent of its known role in stimulating platelet secretion, and represents a common pathway of PS exposure and microvesicle release induced via several different agonists. This novel PS exposure and microvesculation mechanism is important for the function of platelets to promote coagulation.
Abstract 19003: The Molecular Basis of Cooperative Transcriptional Regulation by Foxo1 and Ets1 on a Conserved Endothelial Cell-Specific Enhancer Site Determined by the Ternary Complex Crystal Structure
Authors: Birrane Gabriel , Choy Wing C , Geiger Catherine A , Grant Marianne A
Published: April 2024

Establishment and maintenance of the vasculature is mediated by a highly organized transcriptional program requiring the correct spatial and temporal expression of a large number of genes. Evidence suggests that endothelial-specific gene expression may be regulated combinatorially by transcription factor partnerships. However, no understanding of the molecular basis for mechanisms governing endothelial-specific synergistic gene expression yet exists. Here, we show the molecular basis for a transcription factor partnership on an enhancer that is sufficient to direct expression specifically and exclusively to the developing vascular endothelium. This
cis
-acting enhancer element is bound and activated by Forkhead (FOX) and ETS transcription factors and also plays a role in the expression of genes important for adult neovascularization and vascular integrity. We have determined the 2.7Å resolution crystal structure of the DNA-binding domain of FOXO1 (FOXO1-DBD) and the DNA-binding domain of ETS1 (ETS1-DBD) bound to a 21-bp DNA duplex of the composite FOX:ETS endothelial-specific site. The ternary complex structure reveals the ETS1-DBD α/β architecture with three α-helices packed against four antiparallel β-strands to form a ‘winged helix-turn-helix’ topology and with helix-α3 embedded in the major groove. FOXO1-DBD in the complex displays a ‘winged-helix’ architecture with helix-α3 binding the major groove base sequence AATAA. Loop region H2-H3 of FOXO1-DBD is stabilized into a unique conformation to make salt-bridge mediated contact with ETS1 in the minor groove. The ternary complex structure reveals the molecular details of selective recruitment of FOXO1 by ETS1 to this non-canonical FOX:ETS site. These findings are supported by EMSA studies showing FOXO1-DBD binds poorly to FOX:ETS DNA in the absence of ETS1-DBD and underscores the cooperativity of ETS and FOX activities on the
cis
-acting sequence. This important ternary complex provides understanding of how FOX and ETS synergistically mediate transcriptional activity on an enhancer directing expression specifically and exclusively to the developing vasculature, as well as cooperatively regulate gene expression in adult neovascularization and vascular hemostasis.
Abstract 19016: ALK2 and ALK3 BMP Type I Receptors Are Required for the Development of Cardiac Hypertrophy
Authors: Shahid Mohd , Spagnolli Ester , Ernande Laura , Kolodziej Starsha , Mayeur Claire , Leyton Patricio , Scherrer-Crosbie Marielle , Bloch Kenneth D
Published: April 2024

Bone Morphogenetic Proteins (BMP) signaling is required for the development of cardiac hypertrophy. BMP signaling mediates its action via BMP type I and type II receptors. We sought to determine which type I receptors are required for cardiac hypertrophy.

We studied BMP signaling in neonatal rat cardiomyocytes (NRCs) stimulated with phenylephrine (PE) or isoproterenol (ISO). In comparison with untreated NRCs, PE (10 μM) and ISO (10 μM) induced hypertrophy, as reflected by increases in cell size (457±50 and 401±35 vs 254±23 μm2, p<0.01) and expression of the gene encoding B-type natriuretic peptide (NPPB; 4.0±1.0 and 3.2±0.8-fold, p<0.01). PE and ISO induced expression of genes specifying BMP2 (6.7±0.5 and 5.6±0.6-fold), BMP7 (4.1±0.4 and 3.6±0.9-fold), and the BMP target gene, Id-1, (3.7±0.1 and 4.2±1.0-fold, p<0.001). PE and ISO also induced phosphorylation of BMP-responsive Smads 1 and 5 and increased activity of a BMP response element-luciferase reporter (14.5±0.8 and 11.9±1.1 vs 5.4±0.4, p<0.01). Incubation of NRCs with the BMP inhibitors, LDN193189 (100 nM) or noggin (100 ng/ml), markedly suppressed the ability of PE and ISO to increase cell size, NPPB gene expression, and Smad1/5 phosphorylation. qRT-PCR analysis revealed that ALK2 and ALK3 were highly expressed in NRC, whereas ALK1 and ALK6 were expressed at very low levels. siRNA-mediated silencing of ALK2 or ALK3, but not ALK1 or ALK6, blocked PE-induced hypertrophy in NRCs. Using cardiomyocytes from ALK1flox/flox and ALK2flox/flox neonatal mice infected with Ad-Cre (to delete the floxed allele) or Ad-RFP (as a control) revealed that PE-induced hypertrophy requires Alk2 but not Alk1.

Based on these observations, we conclude that BMP signaling is upregulated in NRCs in response to hypertrophic stimuli. ALK2 and ALK3 appear to be the BMP type I receptors which are required for the development of hypertrophy in neonatal cardiac myocytes.
Abstract 19031: Utilization and Outcomes of Anti-Tachycardia Pacing Therapy in Children and Young Adults With Implantable-Cardioverter Defibrillators
Authors: Janson Chris , Shah Maully
Published: April 2024

Background:
Inappropriate and unnecessary ICD shocks are a concern in the growing pediatric device population. Historically, ICDs have been programmed as “shock boxes,” with a single therapy zone for ventricular fibrillation (VF). Adult trials have demonstrated safe shock reduction by programming a second zone for ventricular tachycardia (VT), with anti-tachycardia pacing (ATP) as initial therapy. The utilization and outcomes of ATP therapy have not been described in the pediatric population.

Methods:
Subjects ≤ 30 years of age with ICDs implanted at a single tertiary pediatric center between 9/30/2009 and 9/30/2012 were included. Patient characteristics, ICD programming, and outcomes were retrospectively reviewed.

Results:
45 patients underwent ICD implantation at a mean age of 13.9 ± 4 years (55% primary electrical disorder, 36% cardiomyopathy, 9% congenital heart disease). A primary prevention indication was present in 64% (n=29). A single VF zone with shock therapy only was programmed in 32 patients (71%). Thirteen patients (29%) had a second VT zone with ATP as initial therapy. Of 11 patients with a history of monomorphic VT, 45% (n=5) had two zone programming. ATP during charging was programmed in the VF zone in 91% of devices. At a median follow-up of 19.2 months (IQR 8.4-26.1 months), 37 events (2 VF, 28 monomorphic VT, 7 polymorphic VT) met criteria for therapy in 4 patients; 16 (43%) events were treated with shocks, including 9 that required multiple shocks; 21 (57%) events, all monomorphic VT, were pace-terminated in 2 patients. ATP was successful in 21 of 22 (95%) attempts. In 3 events, VT terminated with ATP while charging, so shocks were aborted. There were no syncopal events due to delay in shocks by ATP failure. There was no difference in the number of inappropriate shocks between single (n=6) and two zone (n=4) programming groups, although 2 patients with two zone programming were shocked for sinus tachycardia in the VT zone.

Conclusions:
The pediatric ICD population is heterogeneous, making it difficult to adopt a uniform programming strategy. ATP can prevent unnecessary shocks in children with monomorphic VT. Two zone programming should be considered for patients at risk for monomorphic VT.
Abstract 19052: Readmissions After Implantation of Continuous-Flow Left Ventricular Assist Devices: A Comparison Between the HeartMate II and the HeartWare Devices
Authors: Haglund Nicholas A , Davis Mary E , Gallion Anna H , Ahmad Rashid A , DiSalvo Thomas J , Keebler Mary E , Lenihan Daniel J , Schlendorf Kelly H , Wigger Mark A , Maltais Simon
Published: April 2024

Background:
Readmissions after implantation of continuous-flow left ventricular assist devices (CF-LVAD) are common. The ADVANCE Trial fails to compare readmissions between the HeartMate II (HMII) LVAD and the HeartWare VAD (HVAD). We sought to compare the frequency and causes of early (60 day) readmissions after implantation of these two devices.

Methods:
We retrospectively evaluated readmissions at Vanderbilt University Medical Center in a cohort of 65 patients implanted between April 2009 and April 2013 with the HM II LVAD (n= 46) and the HVAD (n=19). All hospitalizations between time of LVAD implant and 60 days were analyzed.

Results:
Preoperative patient characteristics (age, LVEF, % reoperation, % ischemic etiology), and preoperative risk stratification (INTERMACS category, Leitz-Miller score, Kormos score) were comparable between groups (all p>0.05). There were 37 readmissions for 28 patients within the first 60 days after device implant. Twenty-six readmissions (70%) occurred between 0-30 days, 11 (30%) between 30-60 days. Overall, the most common reasons for readmission within the first 60 days of implant were Cardiac (heart failure (7) and arrhythmia (6)) n= 13 (35%), other (dehydration (6), pain (1), VAD disconnect (1), elevated INR (2)) n=10 (27%), infection (driveline (2), non-driveline (4)) n=6 (16%), thrombosis (pump (3), hemolysis (1), stroke (1)) n=5 (14%), and bleeding (gastrointestinal (2), hemorrhagic stroke (1)) n= 3 (8%). Readmission frequency in patients with a HMII versus HVAD device type (27 readmissions in 22 patients with HMII

vs

10 admissions in 7 patients with HVAD) was not different p=0.40.

Conclusion:
Readmission rate after CF-LVAD implantation is frequent (45%) especially within the first 30 days. There are no differences in readmission rate among CF-LVAD types. Understanding these causes is critical for clinical management and institutional efforts to reduce CF-LVAD readmission rates and associated costs.
Abstract 19058: Role of Agxt2 in Metabolism of Adma in the Settings of Acute Elevation of Systemic Adma Levels
Authors: Rodionov Roman , Martens-Lobenhoffer Jens , Brilloff SIlke , Hohenstein Bernd , Weiss Norbert , Bode-Böger Stefanie M
Published: April 2024

Background:
Endogenous inhibitor of nitric oxide synthases asymmetric dimethylarginine (ADMA) has been proposed to serve as an independent cardiovascular risk factor. The major pathway of ADMA degradation is hydrolysis catalyzed by dimethylarginine dimethylaminohydrolase (DDAH). ADMA can also be metabolized through a different pathway, by alanine:glyoxylate aminotransferase 2 (AGXT2), with the formation of α-keto-δ-(N,N-dimethylguanidino)valeric acid (DMGV). The goal of this study was to better characterize the role of the AGXT2 pathway in metabolism of ADMA in vivo using a recently developed assay for detection of DMGV in biological samples.

Methods:
ADMA (250 μmol x kg-1 x d-1) was infused in C57/BL6 mice for 3 days using osmotic minipumps implanted intraperitoneally. We performed bilateral nephrectomy in some of the mice 24 hours before the end of ADMA infusion and sample collection. Measurements of ADMA and DMGV were performed LC-MS/MS.

Results:
Infusion of ADMA for 3 days resulted in a 3.4 fold increase in plasma and in a 5.2 fold increase in urine ADMA levels. Elevation of ADMA concentration coincided with elevation of plasma and urine DMGV levels (2.9 and 3.9 folds respectively). Bilateral nephrectomy in the mice, which did not undergo ADMA infusion, did not increase plasma ADMA levels, while bilateral nephrectomy in the mice, which underwent ADMA infusion, led to a 1.7 fold increase in plasma ADMA levels and a 17.6 fold increase in DMGV levels. Neither bilateral nephrectomy nor infusion of ADMA for 3 days changed the AGXT2 mRNA levels in the liver.

Conclusions:
Infusion of ADMA leads to increased flux through the AGXT2 pathway of ADMA metabolism in vivo. The observation that each 1 μmol / mmol creatinine increase in ADMA level in urine leads to about 1 μmol / mmol creatinine increase in urine DMGV level suggests that AGXT2 is a major enzyme regulating ADMA levels in urine. The marked increase in DMGV levels in the mice lacking both kidneys suggests significant extrarenal production of DMGV in addition to absent renal excretion. Lack of increase in plasma ADMA levels after nephrectomy in mice infused with saline suggests that ADMA-metabolyzing ezymes are able to compensate for lack of renal excretion of ADMA in our model.
Abstract 19079: Cd13 and Ror2 Markers of Pre-Cardiac Mesoderm
Authors: Skelton Rhys , Brady Bevin , Weissman Irving , Elliott David A , Ardehali Reza
Published: April 2024

The human heart has a limited regenerative capacity and there is an unmet demand for improved therapies for myocardial disease. Human embryonic stem cell (hESC) derived cardiomyocytes have potential to facilitate the development of both cell-based and pharmaceutical treatments. To date many studies have focused on the efficient generation of cardiomyocytes from hESCs. However, its clinical use has been limited by technical challenges, including the inability to isolate a pure population of cardiovascular progenitors capable of robust engraftment and regeneration. To this end, we have attempted to identify surface markers that facilitate isolation of cardiac mesoderm and cardiovascular progenitors from differentiating hESCs.

Lineage-specific reporter hESC lines (MIXL1-GFP and NKX2.5-GFP) were utilized to test prospective isolation of early cardiac progenitors using two novel cell surface markers, CD13 and ROR2. A distinct population of cells co-expressing CD13 and ROR2 was isolated after 3 days of hESC differentiation which exhibited a transcriptional profile similar to primitive streak/mesoderm cells. Gene expression analysis and immunostaining confirmed the enrichment of mesodermal cells and near complete removal of endodermal, ectodermal and undifferentiated cells. To quantify the extent of cardiovascular progenitors generated from CD13/ROR2 expressing cells, an NKX2.5-GFP reporter hESC line was used and the double positive cells were sorted after 3 days and maintained in culture for 14 days. The majority of these cells showed enrichment for cardiovascular cells based on gene and protein expression, phenotype, and transplantation studies. By enabling retrieval of early mesoderm precursors from heterogeneous differentiated hESC populations, we anticipate CD13 and ROR2 should have utility in enriching for subsequent cardiac potential_the necessary first developmental step towards creating purified cardiomyocytes from hESC.
Abstract 19080: Peak Exercise Capacity is a Poor Indicator of Functional Capacity for Patients Supported by a Continuous Flow Left Ventricular Assist Device
Authors: Nahumi Nadav , Garan Arthur R , Uriel Nir , Han Jason , Morrison Kerry A , Thomas Sunu S , Yuzefpolskaya Melana , Colombo Paolo C , Jorde Ulrich P
Published: April 2024

Introduction:
Six minute walk distance (6MWD) has been shown to be linearly related to peak oxygen uptake (VO2) during maximal exercise for patients suffering from heart failure (HF); however, this relationship in patients supported by left ventricular assist devices (CF-LVAD) is not well understood.

Hypothesis:
CF-LVADs readily support sub-maximal exercise such as walking, but this improvement is not accompanied by increased maximal exercise capacity due to relatively fixed cardiac output assistance provided by the LVAD.

Methods:
Forty patients with HF and 29 patients supported by LVADs performed a 6-minute walk test and a maximal cardiopulmonary exercise test.

Results:
The peak VO2 was linearly correlated with 6MWD in both HF (r=0.58, p<0.001) and LVAD patients (r=0.53, p=0.003). While the slopes were similar, b=0.025 and b=0.029 for CHF and LVAD, respectively, patients with HF had a greater peak VO2 than patients supported by LVADs who achieved the same 6MWD. CF-LVAD patients walked approximately 80 meters more than HF patients in a 6-minute walk test for any given peak VO2.

Conclusions:
For any given peak VO2, patients supported by LVAD may have a greater functional capacity than HF patients. Peak VO2 should not be used as an outcome variable in clinical trials assessing functional capacity after LVAD implantation.
Abstract 19091: Platelet mTOR is an Important Mediator of Arterial Thrombosis
Authors: Ahn Yong-Joo , Kim Maya Hwewon , Kim Hyung-Hwan
Published: April 2024

Background:
Arterial thrombosis is responsible for peripheral vascular disease, ischemic stroke, and myocardial infarction. Mammalian target of rapamycin (mTOR) inhibition promotes arterial thrombosis. To determine the contributions of platelet specific mTOR deficiency to arterial thrombosis, we generated platelet specific mTOR deficient mice. To determine the rescue effect of platelet mTOR deficiency, we also generated platelet specific TSC1 deficient (PF4Cre-TSC1

flox/flox

) mice. Because the effect of mTOR activation on thrombus formation
in vivo
has not yet been studied, we hypothesize that mTOR signaling pathway in platelets may play an important role in arterial thrombosis.

Methods and Results:
To determine the role of platelet mTOR in arterial thrombosis, we generated a mouse strain with platelet-specific mTOR deficiency (PF4Cre-mTOR

flox/flox

) using conditional mTOR

flox/flox

mice and platelet-specific PF4Cre mice. PF4Cre-mTOR

flox/flox

mice did not show any obvious phenotypic abnormalities. Arterial thrombus formation was investigated using
in vivo
ferric chloride induced thrombosis model. Ferric Chloride (5% FeCl
3
) induced thrombotic occlusion. Rapamycin treatment and mTOR conditional knockout induced arterial thrombosis significantly. Compared to PF4Cre mice, PF4Cre-TSC1

flox/flox

mice exhibited elongated thrombotic occlusion time by 51.7%. Platelet specific mTOR deficiency induced arterial thrombosis quickly compare to the WT
via
activation of p-S6, a downstream target of mTORC1 and inhibition of p-Rictor of mTORC2.

Conclusion:
These finding indicate that platelet specific mTOR deficiency resulted in significantly induced arterial thrombosis but delayed at the platelet specific TSC1 deficient mice. These results suggest that activation of mTORC1 may have therapeutic benefits in arterial thrombosis.
Abstract 19102: Cardiac Specific Ablation of SAP97 Alters Normal Excitability of the Murine Heart
Authors: Musa Hassan , Carleton Lena , O’Connell Ryan P , Gomez Mario , Guerrero-Serna Guadalupe , Milstein Michelle , Herron Todd , Stein Adam , Anumonwo Justus M
Published: April 2024

Synapse-associated protein 97 (SAP97) is a scaffolding protein and is the archetypical MAGUK. In vitro studies suggest that SAP97 regulates expression of cardiac Na and K channels, and may be important for cardiac excitation.

OBJECTIVES:
To generate a model for inducible, targeted SAP97 ablation, and to investigate arrhythmia susceptibility and the underlying cellular/molecular mechanisms.

Methods:
SAP97 targeted deletion was generated using the Cre-Lox system. Animals were subjected to biochemistry, electrophysiology, echo- and electrocardiographic analyses.

Results:
Western blot analyses demonstrated SAP97 ablation was specific to the myocardium. Test animals showed several ECG abnormalities; including changes in P waves, premature atrial contractions, and prolongations in ST and QT intervals. ST interval averaged (ms) 22.3±2.53 (heterozygote) compared to 15.9±0.98 (control; p=0.03). ST prolongation was more pronounced (34.8±2.22 ms) in homozygote than in heterozygote mice; p< 0.001. Similarly, QT interval was much longer in homozygote than in heterozygote animals, both of which were longer than control values (p<0.001; n=13-15 in each group). In isolated ventricular cells, action potential duration at 80% repolarization; (APD80) were significantly longer in test animals compared to controls. Thus, control APD80 (ms) was 11.6±2.38 versus 47.19±11.27 in heterozygote animals (p=0.012). APD prolongation was more severe in homozygote animals. Early after depolarizations were more prevalent in test mice, compared to control. Data in cells isolated from control and homozygote mouse hearts showed significant changes in INa, ITO and IK1 current densities following SAP97 ablation. Control densities of ITO and IK1 were (pA/pF) 43.68±3.91 (+60mV) and -18.13±0.95 (-120mV) and were 19.96±2.48 and -12.38±0.64 after SAP97 ablation. In contrast, INa density was upregulated, averaging (pA/pF) -32.52±4.60 (-50mV) in control and -47.53±4.47 after SAP97 ablation.

Conclusion:
SAP97 is important for normal functionality of cardiac ion channels in the murine myocardium, and its ablation predisposes to arrhythmogenicity. Our model of targeted SAP97 ablation is important for understanding the role of SAP97 in cardiac excitation.