Nuclear GAPDH in cortical microglia mediates cellular stress-induced cognitive inflexibility.

We report a mechanism that underlies stress-induced cognitive inflexibility at the molecular level. In a mouse model under subacute cellular stress in which deficits in rule shifting tasks were elicited, the nuclear glyceraldehyde dehydrogenase (N-GAPDH) cascade was activated specifically in microglia in the prelimbic cortex. The cognitive deficits were normalized with a pharmacological intervention with a compound (the RR compound) that selectively blocked the initiation of N-GAPDH cascade without affecting glycolytic activity. The normalization was also observed with a microglia-specific genetic intervention targeting the N-GAPDH cascade. At the mechanistic levels, the microglial secretion of High-Mobility Group Box (HMGB), which is known to bind with and regulate the NMDA-type glutamate receptors, was elevated. Consequently, the hyperactivation of the prelimbic layer 5 excitatory neurons, a neural substrate for cognitive inflexibility, was also observed. The upregulation of the microglial HMGB signaling and neuronal hyperactivation were normalized by the pharmacological and microglia-specific genetic interventions. Taken together, we show a pivotal role of cortical microglia and microglia-neuron interaction in stress-induced cognitive inflexibility. We underscore the N-GAPDH cascade in microglia, which causally mediates stress-induced cognitive alteration.

Reduction of left ventricular diastolic pressure as a key regulator of infarct coronary flow under mechanical left ventricular support.

Restoring ischaemic myocardial tissue perfusion is crucial for minimizing infarct size. Acute mechanical left ventricular (LV) support has been suggested to improve infarct tissue perfusion. However, its regulatory mechanism remains unclear. We investigated the physiological mechanisms in six Yorkshire pigs, which were subjected to 90-min balloon occlusion of the left anterior descending artery. During the acute reperfusion phase, LV support using an Impella heart pump was initiated. LV pressure, coronary flow and pressure of the infarct artery were simultaneously recorded to evaluate the impact of LV support on coronary physiology. Coronary wave intensity was calculated to understand the forces regulating coronary flow. Significant increases in coronary flow velocity and its area under the curve were found after mechanical LV support. Among the coronary flow-regulating factors, coronary pressure was increased mainly during the late diastolic phase with less pulsatility. Meanwhile, LV pressure was reduced throughout diastole resulting in significant and consistent elevation of coronary driving pressure. Interestingly, the duration of diastole was prolonged with LV support. In the wave intensity analysis, the duration between backward suction and pushing waves was extended, indicating that earlier myocardial relaxation and delayed contraction contributed to the extension of diastole. In conclusion, mechanical LV support increases infarct coronary flow by extending diastole and augmenting coronary driving pressure. These changes were mainly driven by reduced LV diastolic pressure, indicating that the key regulator of coronary flow under mechanical LV support is downstream of the coronary artery, rather than upstream. Our study highlights the importance of LV diastolic pressure in infarct coronary flow regulation. KEY POINTS: Restoring ischaemic myocardial tissue perfusion is crucial for minimizing infarct size. Although mechanical left ventricular (LV) support has been suggested to improve infarct coronary flow, its specific mechanism remains to be clarified. LV support reduced LV pressure, and elevated coronary pressure during the late diastolic phase, resulting in high coronary driving pressure. This study demonstrated for the first time that mechanical LV support extends diastolic phase, leading to increased infarct coronary flow. Future studies should evaluate the correlation between improved infarct coronary flow and resulting infarct size.

Impact of ischemia on left atrial remodeling and dysfunction in swine models of mitral regurgitation.

Left atrial (LA) dysfunction is one of the predictive factors of worse outcomes after mitral valve surgery for mitral regurgitation (MR). We aimed to investigate the effect of MR etiology on progression of LA remodeling in swine MR models. MR was induced in 14 Yorkshire pigs using catheter-based procedures. Seven pigs underwent simultaneous occlusions of the left circumflex artery and the diagonal branch, which resulted in ischemic mitral regurgitation (IMR group). The other seven pigs underwent chordal severing to induce leaflet prolapse simulating degenerative mitral regurgitation (DMR group). Changes in LA volume and function were assessed at baseline, 1 mo, and 3 mo using echocardiography and hemodynamic evaluations. Histopathological assessments were conducted to evaluate LA hypertrophy and fibrosis. At 3 mo, quantitative MR severity was comparable and severe in both groups. Despite the similar degree of MR, minimum LA volume index increased significantly more in the IMR group (IMR: 11.9 ± 6.4 to 73.2 ± 6.4 mL/m2, DMR: 10.7 ± 6.4 to 29.5 ± 6.4 mL/m2, Pinteraction = 0.004). Meanwhile, increase in maximum LA volume index was similar between the groups, resulting in lower LA emptying function in the IMR group (IMR: 60.1 ± 3.1 to 29.4 ± 3.1%; DMR: 62.4 ± 3.1 to 58.2 ± 3.1%, Pinteraction = 0.0003). LA reservoir strain assessed by echocardiography was also significantly lower in the IMR group. Histological analyses revealed increased LA cellular hypertrophy and fibrosis in the IMR group. In conclusion, ischemic MR is associated with aggressive remodeling and reduced emptying function compared with the MR due to leaflet prolapse. Earlier intervention might be necessary for ischemic MR to prevent LA remodeling.NEW & NOTEWORTHY We show different LA structural and functional remodeling patterns between ischemic MR and MR due to leaflet prolapse. Severe ischemic MR was accompanied by extensive LA remodeling, which may be associated with poor clinical outcomes. Our data suggest that detailed structural and functional LA remodeling assessment is important for managing IMR and to determine the presence of LA ischemia.

A pacing-controlled protocol for frequency-diastolic relations distinguishes diastolic dysfunction specific to a mouse HFpEF model.

Heart failure with preserved ejection fraction (HFpEF), characterized by diastolic dysfunction and insufficient exercise capacity, is a growing health problem worldwide. One major difficulty with experimental research on HFpEF is the lack of methods to consistently detect diastolic dysfunction in mouse models. We developed a pacing-controlled pressure-volume (PV) loop protocol for the assessment of diastolic function at different heart rates in mice and tested if the protocol could detect diastolic dysfunction specific to a HFpEF model. A HFpEF model was generated by high-fat diet (HFD) feeding with concomitant NG-nitro-l-arginine methyl ester administration, and a pressure-overload hypertrophy (PO) model was produced by surgical constriction of the transverse aorta (TAC). Heart rate (HR) was slowed below 400 beats/min by intraperitoneal injection of ivabradine. PV loop data were acquired and analyzed at HR incrementing from 400 to 700 beats/min via atrial pacing using a miniature pacing catheter inserted into the esophagus, and comparisons were made among control, HFpEF, and PO mice. At baseline without pacing, no diastolic abnormalities were detected in either PO or HFpEF models. Frequency-diastolic relations, however, revealed the significant diastolic impairment specific to the HFpEF model; both relaxation time constant (Tau) and end-diastolic pressure-volume relationship (EDPVR) were worsened as heart rate increased. Peak positive first derivative of left ventricular pressure (dP/dtmax) was significantly lower in HFpEF versus controls only at a high HR of 700 beats/min. A pacing-controlled protocol would be a feasible and potent method to detect diastolic dysfunction specific to a mouse HFpEF model.NEW & NOTEWORTHY We developed a pacing-controlled PV loop protocol for the assessment of diastolic function at different heart rates in mice, which is a feasible and potent method for the characterization of diastolic dysfunction in a murine HFpEF model whose diastolic dysfunction might be difficult to be detected under resting conditions without pacing.

TEE image quality improvement with our devised probe cover.

OBJECTIVE(S): Our hypothesis was that our devised transesophageal echocardiography probe cover with the capacity for pinpoint suction would improve image quality. DESIGN: Prospective cohort study. SETTING: Single tertiary medical center. PARTICIPANTS: Patients undergoing surgery requiring intraoperative transesophageal echocardiography. INTERVENTIONS: Suctioning with inserted orogastric tube. MEASUREMENTS AND MAIN RESULTS: Changes in image quality with suctioning were assessed by 2 methods. In method #1, investigators categorized the quality of all acquired images on a numeric scale based on each investigator's impression (1: very poor, 2: poor, 3: acceptable, 4: good, and 5: very good). In method #2, the reproducibility of the left ventricular fraction area change (LV FAC) was assessed, assuming that improved transgastric midpapillary short-axis view image quality would yield better LV FAC reproducibility. With method #1, for midesophageal views, 26.5%, 70.5%, and 3.0% of images showed improved, the same, and worsened image quality, respectively. For transgastric views, 55.3%, 43.3%, and 1.4% showed improved, the same, and worsened image quality, respectively. For deep transgastric views, 60.0%, 38.0%, and 2.0% showed improved, the same, and worsened image quality, respectively. With method #2, the presuction group had an ICC of 0.942 (95% CI: 0.91, 0.965). The postsuction group had an ICC of 0.988 (95% CI: 0.981, 0.993). CONCLUSIONS: Our investigation validates the potential image quality improvement withour devised TEE probe cover. However, its clinical validity needs to be confirmed by further studies.

Hepatic Vein Flow Index During Orthotopic Liver Transplantation as a Predictive Factor for Postoperative Early Allograft Dysfunction.

OBJECTIVES: The authors devised a hepatic vein flow index (HVFi), using intraoperative transesophageal echocardiography and graft weight, and investigated its predictive value for postoperative graft function in orthotopic liver transplant. DESIGN: Prospective clinical trial. SETTING,: Single-center tertiary academic hospital. PARTICIPANTS: Ninety-seven patients who had orthotopic liver transplant with the piggy-back technique between February 2018 and December 2019. MEASUREMENTS AND MAIN RESULTS: HVFi was defined with HV flow/graft weight. Patients who developed early graft dysfunction (EAD) had low HVFi in systole (HVFi sys, 1.23 v 2.19 L/min/kg, p < 0.01), low HVFi in diastole (HVFi dia, 0.87 v 1.54 L/min/kg, p < 0.01), low hepatic vein flow (HVF) in systole (HVF sys, 2.04 v 3.95 L/min, p < 0.01), and low HVF in diastole (HVF dia, 1.44 v 2.63 L/min, p < 0.01). More cardiac death, more vasopressors at the time of measurement, more acute rejection, longer time to normalize total bilirubin (TIME t-bil), longer surgery time, longer neohepatic time, and more packed red blood cell transfusion were observed in the EAD patients. All HVF parameters were negatively correlated with TIME t-bil (HVFi sys R = -0.406, p < 0.01; HFVi dia R = -0.442, p < 0.01; HVF sys R = -0.44, p < 0.01; HVF dia R = -0.467, p < 0.01). The receiver operating characteristic curve analysis determined the best cut-off levels of HVFi to predict occurrence of EAD (HVFi sys <1.608, HVFi dia <0.784 L/min/kg), acute rejection (HVFi sys <1.388, HVFi dia <1.077 L/min/kg), and prolonged high total bilirubin (HVFi sys <1.471, HVFi dia <1.087 L/min/kg). CONCLUSIONS: The authors' devised HVFi has the potential to predict the postoperative graft function.

Impaired left ventricular global longitudinal strain is associated with elevated left ventricular filling pressure after myocardial infarction.

Left ventricular (LV) global longitudinal strain (GLS) has emerged as a significant prognostic marker in patients after myocardial infarction (MI). Although elevated LV filling pressure after MI might alter GLS, direct evidence for this is lacking. This study aimed to clarify the association between GLS and LV filling pressure in a large animal MI model. A total of 104 Yorkshire pigs underwent both echocardiographic and hemodynamic assessments 1-4 wk after induction of large anterior MI. GLS was measured in the apical four-chamber view using a semiautomated speckle-tracking software. LV pressure-volume relationship was invasively measured using a high-fidelity pressure-volume catheter. GLS >-14% was considered impaired. Compared with pigs with LV ejection fraction (LVEF) >40% and preserved GLS (n = 29), those with LVEF >40% and impaired GLS (n = 37) and those with LVEF ≤40% (n = 38) had significantly higher LV end-diastolic pressure (15.5 ± 5.5 vs. 19.7 ± 5.8 and 19.6 ± 6.6 mmHg; P = 0.008 and P = 0.026, respectively) and higher LV mean diastolic pressure (7.1 ± 2.9 vs. 10.4 ± 4.5 and 11.1 ± 5.4 mmHg; P = 0.013 and P = 0.002, respectively). GLS was modestly correlated with τ (r = 0.21, P = 0.039) and slope of LV end-diastolic pressure-volume relationship (r = 0.43, P < 0.001). Impaired GLS was associated with higher LV end-diastolic and mean-diastolic pressures after adjusting for LVEF and baseline characteristics (P = 0.026 and P = 0.001, respectively). Impaired GLS assessed by speckle-tracking echocardiography was associated with elevated LV filling pressure after MI. GLS has an incremental diagnostic value for detecting elevated LV filling pressure and may be particularly useful for evaluating post-MI patients with preserved LVEF.NEW & NOTEWORTHY Strain analysis was performed in 104 pigs after MI, and its relationship to invasive hemodynamic measurements was studied. Impaired longitudinal strain was associated with high ventricular filling pressure independent of LVEF in post-MI setting. Global longitudinal strain is a potential prognostic marker after MI.

High-throughput single-molecule RNA imaging analysis reveals heterogeneous responses of cardiomyocytes to hemodynamic overload.

BACKGROUND: The heart responds to hemodynamic overload through cardiac hypertrophy and activation of the fetal gene program. However, these changes have not been thoroughly examined in individual cardiomyocytes, and the relation between cardiomyocyte size and fetal gene expression remains elusive. We established a method of high-throughput single-molecule RNA imaging analysis of in vivo cardiomyocytes and determined spatial and temporal changes during the development of heart failure. METHODS AND RESULTS: We applied three novel single-cell analysis methods, namely, single-cell quantitative PCR (sc-qPCR), single-cell RNA sequencing (scRNA-seq), and single-molecule fluorescence in situ hybridization (smFISH). Isolated cardiomyocytes and cross sections from pressure overloaded murine hearts after transverse aortic constriction (TAC) were analyzed at an early hypertrophy stage (2 weeks, TAC2W) and at a late heart failure stage (8 weeks, TAC8W). Expression of myosin heavy chain ß (Myh7), a representative fetal gene, was induced in some cardiomyocytes in TAC2W hearts and in more cardiomyocytes in TAC8W hearts. Expression levels of Myh7 varied considerably among cardiomyocytes. Myh7-expressing cardiomyocytes were significantly more abundant in the middle layer, compared with the inner or outer layers of TAC2W hearts, while such spatial differences were not observed in TAC8W hearts. Expression levels of Myh7 were inversely correlated with cardiomyocyte size and expression levels of mitochondria-related genes. CONCLUSIONS: We developed a new image-analysis pipeline to allow automated and unbiased quantification of gene expression at the single-cell level and determined the spatial and temporal regulation of heterogenous Myh7 expression in cardiomyocytes after pressure overload.

Multi-scale, tailor-made heart simulation can predict the effect of cardiac resynchronization therapy.

BACKGROUND: The currently proposed criteria for identifying patients who would benefit from cardiac resynchronization therapy (CRT) still need to be optimized. A multi-scale heart simulation capable of reproducing the electrophysiology and mechanics of a beating heart may help resolve this problem. The objective of this retrospective study was to test the capability of patient-specific simulation models to reproduce the response to CRT by applying the latest multi-scale heart simulation technology. METHODS AND RESULTS: We created patient-specific heart models with realistic three-dimensional morphology based on the clinical data recorded before treatment in nine patients with heart failure and conduction block treated by biventricular pacing. Each model was tailored to reproduce the surface electrocardiogram and hemodynamics of each patient in formats similar to those used in clinical practice, including electrocardiography (ECG), echocardiography, and hemodynamic measurements. We then performed CRT simulation on each heart model according to the actual pacing protocol and compared the results with the clinical data. CRT simulation improved the ECG index and diminished wall motion dyssynchrony in each patient. These results, however, did not correlate with the actual response. The best correlation was obtained between the maximum value of the time derivative of ventricular pressure (dP/dtmax) and the clinically observed improvement in the ejection fraction (EF) (r=0.94, p<0.01). CONCLUSIONS: By integrating the complex pathophysiology of the heart, patient-specific, multi-scale heart simulation could successfully reproduce the response to CRT. With further verification, this technique could be a useful tool in clinical decision making.

PYK2 mediates BzATP-induced extracellular matrix proteins synthesis.

Mechanical stimuli such as fluid shear and cyclic tension force induced extracellular adenosine triphosphate (ATP) release in osteoblasts. In particular, cyclic tension force-induced ATP enhances bone formation through P2X7 activation. Proline-rich tyrosine kinase 2 (PYK2) mediate osteoblasts differentiation is induced by mechanical stimuli. Furthermore, activation of PYK2 also was a response to integrin by mechanical stimuli. Extracellular matrix protein (ECMP)s, which are important factors for bone formation are expressed by osteoblasts. However, the effect of the interaction of 2'(3)-Ο-(4-Benzoylbenzoyl) adenosine-5'-triphosphate (BzATP), which is the agonist of the mechanosensitive receptor P2X7, with PYK2 on ECMP production is poorly understood. Thus, our purpose was to investigate the effects of PYK2 on BzATP-induced ECMP production in osteoblasts. BzATP increased phospho-PYK2 protein expression on days 3 and 7 of culture. Furthermore, the PYK2 inhibitor PF431394 inhibited the stimulatory effect of BzATP on the expression of type I collagen, bone sialoprotein and osteocalcin expression. PF431396 did not inhibit the stimulatory effect of BzATP on osteopontin (OPN) mRNA expression. These results suggest that mechanical stimuli activate P2X7 might induce ECMPs expression through PYK2 except in the case of OPN expression. Altogether, mechanical stimuli-induced ECMPs production might be implicated by extracellular ATP secretion or integrin via PYK2 activation.

Impact of age on left ventricular geometry and diastolic function in elderly patients with treated hypertension.

PURPOSE: Left ventricular (LV) remodelling is observed in numerous patients with hypertension and is a principal cause of heart failure in elderly patients. The aim of this study was to determine the relationships between age and structural/functional LV remodelling observed in elderly hypertensive patients. METHODS: A total of 557 elderly hypertensive patients (mean age: 74.0 ± 8.6 years) with preserved LV systolic function underwent echocardiography and 24-hour blood pressure (BP) measurement. RESULTS: Overall, 41.1% of patients had LV hypertrophy, 77.9% had increased relative wall thickness (RWT) defined as RWT >0.42, and 31.8% had both. Logistic analysis of the entire study population showed that increased RWT was associated with both 24-hour systolic BP (odds ratio (OR) 1.38, 95% confidence interval (CI) 1.12 to 1.70) and age (OR 1.32, 95%CI 1.08 to 1.61), whereas increased RWT was associated only with age (OR 1.61, 95%CI 1.23 to 2.11) after excluding patients with LV hypertrophy. Univariate and multivariate linear regression analyses of all patients showed that LV diastolic echocardiographic parameters were consistently associated with age (p ≤ .001) alone, even considering LV structural changes. CONCLUSIONS: Age was independently correlated with LV concentric/functional changes regardless of LV hypertrophy, suggesting that ageing is independently involved in the progression of LV remodelling.

Expression of area-specific M2-macrophage phenotype by recruited rat monocytes in duct-ligation pancreatitis.

Acute pancreatitis remains a disease of uncertain pathogenesis and no established specific therapy. Previously, we found a predominant increase and active proliferation of macrophages in the inflamed tissues of a rat duct-ligation pancreatitis model. To analyze the origin and possible role of these macrophages, we investigated their in situ cellular kinetics in a rat model of duct-ligation pancreatitis using a recently established method of multicolor immunostaining for macrophage markers and for proliferating cells with ethynyl deoxyuridine. To detect monocyte-derived macrophages, green fluorescent protein-transgenic (GFP(+)) leukocytes were transferred to monocyte-depleted recipients. In the inflamed pancreas, infiltrating macrophages were mainly two phenotypes, CD68(+)CD163(-) round cells and CD68(+)CD163(+) large polygonal cells, both of which showed active proliferation. In the interlobular area, the proportions of CD68(+)CD163(low) and CD68(+)CD163(high) cells increased over time. Most expressed the M2-macrophage markers CD206 and arginase 1. In contrast, in the interacinar area, CD68(+) cells did not upregulate CD163 and CD206, but ~30 % of them expressed the M1 marker nitric oxide synthase 2 on day 4. GFP(+)-recruited cells were primarily CD68(+)CD163(-) monocytes on day 1 and showed phenotypic changes similar to those of the monocyte non-depleted groups. In conclusion, infiltrating macrophages mostly formed two distinct subpopulations in different areas: monocyte-derived macrophages with the M2 phenotype in the interlobular area or non-M2 phenotype in the interacinar area. Involvement of resident macrophages might be minor in this model. These results are the first demonstration of an upregulated M2 phenotype in rat inflammatory monocytes, which may promote tissue repair.

Regulation of Mitochondrial Dynamics by Dynamin-Related Protein-1 in Acute Cardiorenal Syndrome.

Experimental evidence has clarified distant organ dysfunctions induced by AKI. Crosstalk between the kidney and heart, which has been recognized recently as cardiorenal syndrome, appears to have an important role in clinical settings, but the mechanisms by which AKI causes cardiac injury remain poorly understood. Both the kidney and heart are highly energy-demanding organs that are rich in mitochondria. Therefore, we investigated the role of mitochondrial dynamics in kidney-heart organ crosstalk. Renal ischemia reperfusion (IR) injury was induced by bilateral renal artery clamping for 30 min in 8-week-old male C57BL/6 mice. Electron microscopy showed a significant increase of mitochondrial fragmentation in the heart at 24 h. Cardiomyocyte apoptosis and cardiac dysfunction, evaluated by echocardiography, were observed at 72 h. Among the mitochondrial dynamics regulating molecules, dynamin-related protein 1 (Drp1), which regulates fission, and mitofusin 1, mitofusin 2, and optic atrophy 1, which regulate fusion, only Drp1 was increased in the mitochondrial fraction of the heart. A Drp1 inhibitor, mdivi-1, administered before IR decreased mitochondrial fragmentation and cardiomyocyte apoptosis significantly and improved cardiac dysfunction induced by renal IR. This study showed that renal IR injury induced fragmentation of mitochondria in a fission-dominant manner with Drp1 activation and subsequent cardiomyocyte apoptosis in the heart. Furthermore, cardiac dysfunction induced by renal IR was improved by Drp1 inhibition. These data suggest that mitochondrial fragmentation by fission machinery may be a new therapeutic target in cardiac dysfunction induced by AKI.

Tension force-induced ATP promotes osteogenesis through P2X7 receptor in osteoblasts.

Orthodontic tooth movement induces alveolar bone resorption and formation by mechanical stimuli. Force exerted on the traction side promotes bone formation. Adenosine triphosphate (ATP) is one of the key mediators that respond to bone cells by mechanical stimuli. However, the effect of tension force (TF)-induced ATP on osteogenesis is inadequately understood. Accordingly, we investigated the effect of TF on ATP production and osteogenesis in MC3T3-E1 cells. Cells were incubated in the presence or absence of P2X7 receptor antagonist A438079, and then stimulated with or without cyclic TF (6% or 18%) for a maximum of 24 h using Flexercell Strain Unit 3000. TF significantly increased extracellular ATP release compared to control. Six percent TF had maximum effect on ATP release compared to 18% TF and control. Six percent TF induced the expression of Runx2 and Osterix. Six percent TF also increased the expression of extracellular matrix proteins (ECMPs), ALP activity, and the calcium content in ECM. A438079 blocked the stimulatory effect of 6% TF on the expression of Runx2, Osterix and ECMPs, ALP activity, and calcium content in ECM. This study indicated that TF-induced extracellular ATP is released in osteoblasts, suggesting that TF-induced ATP promotes osteogenesis by autocrine action through P2X7 receptor in osteoblasts.

Patient specific simulation of body surface ECG using the finite element method.

BACKGROUND: Recent studies, supported by advances in computer science, have successfully simulated the excitation and repolarization processes of the heart, based on detailed cell models of electrophysiology and implemented with realistic morphology. METHODS: In this study, we extend these approaches to simulate the body surface electrocardiogram (ECG) of specific individuals. Patient-specific finite element models of the heart and torso are created for four patients with various heart diseases, based on clinical data including computer tomography, while the parallel multi-grid method is used to solve the dynamic bi-domain problem. Personalization procedures include demarcation of nonexcitable tissue, allocation of the failing myocyte model of electrophysiology, and modification of the excitation sequence. In particular, the adjustment of QRS morphology requires iterative computations, facilitated by the simultaneous visualization of the propagation of excitation in the heart, average QRS vector in the torso, and 12-lead ECG. RESULTS: In all four cases we obtained reasonable agreement between the simulated and actual ECGs. Furthermore, we also simulated the ECGs of three of the patients under bi-ventricular pacing, and once again successfully reproduced the actual ECG morphologies. Since no further adjustments were made to the heart models in the pacing simulations, the good agreement provides strong support for the validity of the models. CONCLUSIONS: These results not only help us understand the cellular basis of the body surface ECG, but also open the possibility of heart simulation for clinical applications.

Negative Impact of Acute Reloading after Mechanical Left Ventricular Unloading.

Mechanical LV unloading for acute myocardial infarction (MI) is a promising supportive therapy to reperfusion. However, no data is available on exit strategy. We evaluated hemodynamic and cellular effects of reloading after Impella-mediated LV unloading in Yorkshire pigs. First, we conducted an acute study in normal heart to observe effects of unloading and reloading independent of MI-induced ischemic effects. We then completed an MI study to investigate optimal exit strategy on one-week infarct size, no-reflow area, and LV function with different reloading speeds. Initial studies showed that acute reloading causes an immediate rise in end-diastolic wall stress followed by a significant increase in cardiomyocyte apoptosis. The MI study did not result in any statistically significant findings; however, numerically smaller average infarct size and no-reflow area in the gradual reloading group prompt further examination of reloading approach as an important clinically relevant consideration.

Tie2-Cre-Induced Inactivation of Non-Nuclear Estrogen Receptor-α Signaling Abrogates Estrogen Protection Against Vascular Injury.

Using the Cre-loxP system, we generated the first mouse model in which estrogen receptor-α non-nuclear signaling was inactivated in endothelial cells. Estrogen protection against mechanical vascular injury was impaired in this model. This result indicates the pivotal role of endothelial estrogen receptor-α non-nuclear signaling in the vasculoprotective effects of estrogen.