Phosphorylations and Acetylations of Cytochrome c Control Mitochondrial Respiration, Mitochondrial Membrane Potential, Energy, ROS, and Apoptosis.

Cytochrome c (Cytc) has both life-sustaining and cellular death-related functions, depending on subcellular localization. Within mitochondria, Cytc acts as a single electron carrier as part of the electron transport chain (ETC). When released into the cytosol after cellular insult, Cytc triggers the assembly of the apoptosome, committing the cell to intrinsic apoptosis. Due to these dual natures, Cytc requires strong regulation by the cell, including post-translational modifications, such as phosphorylation and acetylation. Six phosphorylation sites and three acetylation sites have been detected on Cytc in vivo. Phosphorylations at T28, S47, Y48, T49, T58, and Y97 tend to be present under basal conditions in a tissue-specific manner. In contrast, the acetylations at K8, K39, and K53 tend to be present in specific pathophysiological conditions. All of the phosphorylation sites and two of the three acetylation sites partially inhibit respiration, which we propose serves to maintain an optimal, intermediate mitochondrial membrane potential (ΔΨm) to minimize reactive oxygen species (ROS) production. Cytc phosphorylations are lost during ischemia, which drives ETC hyperactivity and ΔΨm hyperpolarization, resulting in exponential ROS production thus causing reperfusion injury following ischemia. One of the acetylation sites, K39, shows a unique behavior in that it is gained during ischemia, stimulating respiration while blocking apoptosis, demonstrating that skeletal muscle, which is particularly resilient to ischemia-reperfusion injury compared to other organs, possesses a different metabolic strategy to handle ischemic stress. The regulation of Cytc by these post-translational modifications underscores the importance of Cytc for the ETC, ΔΨm, ROS production, apoptosis, and the cell as a whole.

Complex patch geometry promotes species coexistence through a reverse competition-colonization trade-off.

Explaining the maintenance of diverse species assemblages is a central goal of ecology and conservation. Recent coexistence mechanisms highlight the role of dispersal as a source of the differences that allow similar species to coexist. Here, we propose a new mechanism for species coexistence that is based on dispersal differences, and on the geometry of the habitat patch. In a finite habitat patch with complex boundaries, species with different dispersal abilities will arrange themselves in stable, concentric patterns of dominance. Species with superior competitive and dispersal abilities will dominate the interior of the patch, with inferior species at the periphery. We demonstrate and explain the mechanism on a simple one-dimensional domain, and then on two-dimensional habitat patches with realistic geometries. Finally, we use metrics from landscape ecology to demonstrate that habitat patches with more complex geometries can more easily support coexistence. The factors that underpin this new coexistence mechanism-different dispersal abilities and habitat patches with complex geometries-are common to many marine and terrestrial ecosystems, and it is therefore possible that the mechanism is a common factor supporting diverse species assemblages.

High Sucrose Diet-Induced Subunit I Tyrosine 304 Phosphorylation of Cytochrome c Oxidase Leads to Liver Mitochondrial Respiratory Dysfunction in the Cohen Diabetic Rat Model.

The mitochondrial oxidative phosphorylation process generates most of the cellular energy and free radicals in mammalian tissues. Both factors play a critical role in numerous human diseases that could be affected by reversible phosphorylation events that regulate the function and activity of the oxidative phosphorylation complexes. In this study, we analyzed liver mitochondria of Cohen diabetes-sensitive (CDs) and Cohen diabetes-resistant (CDr) rats, using blue native gel electrophoresis (BN-PAGE) in combination with mitochondrial activity measurements and a site-specific tyrosine phosphorylation implicated in inflammation, a known driver of diabetes pathology. We uncovered the presence of a specific inhibitory phosphorylation on tyrosine 304 of catalytic subunit I of dimeric cytochrome c oxidase (CcO, complex IV). Driven by a high sucrose diet in both CDr and CDs rats, Y304 phosphorylation, which occurs close to the catalytic oxygen binding site, correlates with a decrease in CcO activity and respiratory dysfunction in rat liver tissue under hyperglycemic conditions. We propose that this phosphorylation, specifically seen in dimeric CcO and induced by high sucrose diet-mediated inflammatory signaling, triggers enzymatic activity decline of complex IV dimers and the assembly of supercomplexes in liver tissue as a molecular mechanism underlying a (pre-)diabetic phenotype.

Developing the VA Geriatric Scholars Programs' Clinical Dashboards Using the PDSA Framework for Quality Improvement.

BACKGROUND: Involving clinician end users in the development process of clinical dashboards is important to ensure that user needs are adequately met prior to releasing the dashboard for use. The challenge with following this approach is that clinician end users can undergo periodic turnover, meaning, the clinicians that played a role in the initial development process may not be the same individuals that use the dashboard in future. OBJECTIVES: Here, we summarize our Plan, Do, Study, Act (PDSA)-guided clinical dashboard development process for the VA Geriatric Scholars Program (GSP) and the value of continuous, iterative development. We summarize dashboard adaptations that resulted from two PDSA cycles of improvement for the potentially inappropriate medication dashboard (PIMD), one of many Geriatric Scholars clinical dashboards. We also present the evaluative performance of the PIMD. METHODS: Evaluation of the PIMD was performed using the system usability scale (SUS) and through review of user interaction logs. Routine end users that were Geriatric Scholars and had evidence of 5 or more dashboard views were invited to complete an electronic form that contained the 10-item SUS. RESULTS: The proportion of Geriatric Scholars that utilized the PIMD increased for each iterative dashboard version that was produced as a byproduct from feedback (31.0% in 2017 to 60.2% in 2019). The overall usability of the PIMD among routine users was found to be above average (SUS score: 75.2 [95% CI 70.5-79.8]) in comparison to the recommended standard of acceptability (SUS score: 68) CONCLUSION: The solicitation of feedback during dashboard orientations led to iterative adaptations of the PIMD that broadened its intended use. The presented PDSA-guided process to clinical dashboard development for the VA GSP can serve as a valuable framework for development teams seeking to produce well-adopted and usable health information technology (IT) innovations.

Sometimes less is more: inhibitory infrared light during early reperfusion calms hyperactive mitochondria and suppresses reperfusion injury.

Ischemic stroke affects over 77 million people annually around the globe. Due to the blockage of a blood vessel caused by a stroke, brain tissue becomes ischemic. While prompt restoration of blood flow is necessary to save brain tissue, it also causes reperfusion injury. Mitochondria play a crucial role in early ischemia-reperfusion injury due to the generation of reactive oxygen species (ROS). During ischemia, mitochondria sense energy depletion and futilely attempt to up-regulate energy production. When reperfusion occurs, mitochondria become hyperactive and produce large amounts of ROS which damages neuronal tissue. This ROS burst damages mitochondria and the cell, which results in an eventual decrease in mitochondrial activity and pushes the fate of the cell toward death. This review covers the relationship between the mitochondrial membrane potential (ΔΨm) and ROS production. We also discuss physiological mechanisms that couple mitochondrial energy production to cellular energy demand, focusing on serine 47 dephosphorylation of cytochrome c (Cytc) in the brain during ischemia, which contributes to ischemia-reperfusion injury. Finally, we discuss the use of near infrared light (IRL) to treat stroke. IRL can both stimulate or inhibit mitochondrial activity depending on the wavelength. We emphasize that the use of the correct wavelength is crucial for outcome: inhibitory IRL, applied early during reperfusion, can prevent the ROS burst from occurring, thus preserving neurological tissue.

Cell-free DNA ultra-low-pass whole genome sequencing to distinguish malignant peripheral nerve sheath tumor (MPNST) from its benign precursor lesion: A cross-sectional study.

BACKGROUND: The leading cause of mortality for patients with the neurofibromatosis type 1 (NF1) cancer predisposition syndrome is the development of malignant peripheral nerve sheath tumor (MPNST), an aggressive soft tissue sarcoma. In the setting of NF1, this cancer type frequently arises from within its common and benign precursor, plexiform neurofibroma (PN). Transformation from PN to MPNST is challenging to diagnose due to difficulties in distinguishing cross-sectional imaging results and intralesional heterogeneity resulting in biopsy sampling errors. METHODS AND FINDINGS: This multi-institutional study from the National Cancer Institute and Washington University in St. Louis used fragment size analysis and ultra-low-pass whole genome sequencing (ULP-WGS) of plasma cell-free DNA (cfDNA) to distinguish between MPNST and PN in patients with NF1. Following in silico enrichment for short cfDNA fragments and copy number analysis to estimate the fraction of plasma cfDNA originating from tumor (tumor fraction), we developed a noninvasive classifier that differentiates MPNST from PN with 86% pretreatment accuracy (91% specificity, 75% sensitivity) and 89% accuracy on serial analysis (91% specificity, 83% sensitivity). Healthy controls without NF1 (participants = 16, plasma samples = 16), PN (participants = 23, plasma samples = 23), and MPNST (participants = 14, plasma samples = 46) cohorts showed significant differences in tumor fraction in plasma (P = 0.001) as well as cfDNA fragment length (P < 0.001) with MPNST samples harboring shorter fragments and being enriched for tumor-derived cfDNA relative to PN and healthy controls. No other covariates were significant on multivariate logistic regression. Mutational analysis demonstrated focal NF1 copy number loss in PN and MPNST patient plasma but not in healthy controls. Greater genomic instability including alterations associated with malignant transformation (focal copy number gains in chromosome arms 1q, 7p, 8q, 9q, and 17q; focal copy number losses in SUZ12, SMARCA2, CDKN2A/B, and chromosome arms 6p and 9p) was more prominently observed in MPNST plasma. Furthermore, the sum of longest tumor diameters (SLD) visualized by cross-sectional imaging correlated significantly with paired tumor fractions in plasma from MPNST patients (r = 0.39, P = 0.024). On serial analysis, tumor fraction levels in plasma dynamically correlated with treatment response to therapy and minimal residual disease (MRD) detection before relapse. Study limitations include a modest MPNST sample size despite accrual from 2 major referral centers for this rare malignancy, and lack of uniform treatment and imaging protocols representing a real-world cohort. CONCLUSIONS: Tumor fraction levels derived from cfDNA fragment size and copy number alteration analysis of plasma cfDNA using ULP-WGS significantly correlated with MPNST tumor burden, accurately distinguished MPNST from its benign PN precursor, and dynamically correlated with treatment response. In the future, our findings could form the basis for improved early cancer detection and monitoring in high-risk cancer-predisposed populations.

Quality Improvement Intervention for Universal Lipid Screening in Children Aged 9 to 11 Years.

We performed a quality improvement intervention to increase universal lipid screening in well-child visits (age 9 to 11 years): 12-month preintervention; phase 1 (8 months) with provider education, group monthly chart review with feedback, and electronic health record cues to order lipids; and phase 2 (16 months) with electronic health record cues and examination room phlebotomy. Outcomes were compared with clinics having no intervention. In phase 1, immediate treatment effect on the regression line for provider behavior (proportion of visits with lipids ordered) showed 34% increase in intervention and 7% decrease in comparison clinics; patient behavior (phlebotomy completed) showed 19% increase in intervention and 5% decrease in comparison clinics. At the beginning of phase 2, the intervention clinic had average 44% orders entered and 33% phlebotomy completed per well-child visit, and these proportions were maintained. Provider education and chart review with feedback were associated with the greatest gains in outcomes.

C-Reactive Protein and Ferritin Are Associated With Organ Dysfunction and Mortality in Hospitalized Children.

Our objective was to determine if C-reactive protein (CRP) and ferritin values alone and in combination are associated with mortality among hospitalized children. All hospitalized patients at our institution with a CRP or ferritin assay in 2015 and 2016 were included. Area under the receiver operating curves (AUROC) were examined, optimal cut-points determined, and patients were stratified into low-, intermediate-, or high-risk groups based on elevation of zero, one, or both biomarkers. A total of 14 928 CRP and 653 ferritin values were obtained, with both obtained for 172 patients. AUROC for maximum CRP value was 0.76 (0.68-0.85) with a cut-point of 7.1 mg/dL for in-hospital mortality and 0.90 (0.83-0.98) for maximum ferritin with a cut-point of 373 ng/mL. Elevation of both ferritin and CRP was associated with the highest inpatient mortality (21.7%) and greatest organ dysfunction, followed by either biomarker alone. Additional prospective study of these biomarkers in combination is warranted.

Acute Neurologic Injury in Children Admitted to the Cardiac Intensive Care Unit.

BACKGROUND: Children with acquired and congenital heart disease both have low mortality but an increased risk of neurologic morbidity that is multifactorial. Our hypothesis was that acute neurologic injuries contribute to mortality in such children and are an important cause of death. METHODS: All admissions to the pediatric cardiac intensive care unit (CICU) from January 2011 through January 2015 were retrospectively reviewed. Patients were assessed for any acute neurologic events (ANEs) during admission, as defined by radiologic findings or seizures documented on an electroencephalogram. RESULTS: Of the 1,573 children admitted to the CICU, the incidence of ANEs was 8.6%. Mortality of the ANE group was 16.3% compared with 1.5% for those who did not have an ANE. The odds ratio for death with ANEs was 8.55 (95% confidence interval, 4.56 to 16.03). Patients with ANEs had a longer hospital length of stay than those without ANEs (41.4 ± 4 vs 14.2 ± 0.6 days; p < 0.001). Need for extracorporeal membrane oxygenation, previous cardiac arrest, and prematurity were independently associated with the presence of an ANE. CONCLUSIONS: Neurologic injuries are common in pediatric CICUs and are associated with an increase in mortality and hospital length of stay. Children admitted to the CICU are likely to benefit from improved surveillance and neuroprotective strategies to prevent neurologic death.

The Pediatric Emergency Care Applied Research Network Registry: A Multicenter Electronic Health Record Registry of Pediatric Emergency Care.

BACKGROUND: Electronic health record (EHR)-based registries allow for robust data to be derived directly from the patient clinical record and can provide important information about processes of care delivery and patient health outcomes. METHODS: A data dictionary, and subsequent data model, were developed describing EHR data sources to include all processes of care within the emergency department (ED). ED visit data were deidentified and XML files were created and submitted to a central data coordinating center for inclusion in the registry. Automated data quality control occurred prior to submission through an application created for this project. Data quality reports were created for manual data quality review. RESULTS: The Pediatric Emergency Care Applied Research Network (PECARN) Registry, representing four hospital systems and seven EDs, demonstrates that ED data from disparate health systems and EHR vendors can be harmonized for use in a single registry with a common data model. The current PECARN Registry represents data from 2,019,461 pediatric ED visits, 894,503 distinct patients, more than 12.5 million narrative reports, and 12,469,754 laboratory tests and continues to accrue data monthly. CONCLUSION: The Registry is a robust harmonized clinical registry that includes data from diverse patients, sites, and EHR vendors derived via data extraction, deidentification, and secure submission to a central data coordinating center. The data provided may be used for benchmarking, clinical quality improvement, and comparative effectiveness research.

Identification of Long Bone Fractures in Radiology Reports Using Natural Language Processing to support Healthcare Quality Improvement.

BACKGROUND: Important information to support healthcare quality improvement is often recorded in free text documents such as radiology reports. Natural language processing (NLP) methods may help extract this information, but these methods have rarely been applied outside the research laboratories where they were developed. OBJECTIVE: To implement and validate NLP tools to identify long bone fractures for pediatric emergency medicine quality improvement. METHODS: Using freely available statistical software packages, we implemented NLP methods to identify long bone fractures from radiology reports. A sample of 1,000 radiology reports was used to construct three candidate classification models. A test set of 500 reports was used to validate the model performance. Blinded manual review of radiology reports by two independent physicians provided the reference standard. Each radiology report was segmented and word stem and bigram features were constructed. Common English "stop words" and rare features were excluded. We used 10-fold cross-validation to select optimal configuration parameters for each model. Accuracy, recall, precision and the F1 score were calculated. The final model was compared to the use of diagnosis codes for the identification of patients with long bone fractures. RESULTS: There were 329 unique word stems and 344 bigrams in the training documents. A support vector machine classifier with Gaussian kernel performed best on the test set with accuracy=0.958, recall=0.969, precision=0.940, and F1 score=0.954. Optimal parameters for this model were cost=4 and gamma=0.005. The three classification models that we tested all performed better than diagnosis codes in terms of accuracy, precision, and F1 score (diagnosis code accuracy=0.932, recall=0.960, precision=0.896, and F1 score=0.927). CONCLUSIONS: NLP methods using a corpus of 1,000 training documents accurately identified acute long bone fractures from radiology reports. Strategic use of straightforward NLP methods, implemented with freely available software, offers quality improvement teams new opportunities to extract information from narrative documents.

Active delivery cable tuned to device deployment state: enhanced visibility of nitinol occluders during preclinical interventional MRI.

PURPOSE: To develop an active delivery system that enhances visualization of nitinol cardiac occluder devices during deployment under real-time magnetic resonance imaging (MRI). MATERIALS AND METHODS: We constructed an active delivery cable incorporating a loopless antenna and a custom titanium microscrew to secure the occluder devices. The delivery cable was tuned and matched to 50Ω at 64 MHz with the occluder device attached. We used real-time balanced steady state free precession in a wide-bore 1.5T scanner. Device-related images were reconstructed separately and combined with surface-coil images. The delivery cable was tested in vitro in a phantom and in vivo in swine using a variety of nitinol cardiac occluder devices. RESULTS: In vitro, the active delivery cable provided little signal when the occluder device was detached and maximal signal with the device attached. In vivo, signal from the active delivery cable enabled clear visualization of occluder device during positioning and deployment. Device release resulted in decreased signal from the active cable. Postmortem examination confirmed proper device placement. CONCLUSION: The active delivery cable enhanced the MRI depiction of nitinol cardiac occluder devices during positioning and deployment, both in conventional and novel applications. We expect enhanced visibility to contribute to the effectiveness and safety of new and emerging MRI-guided treatments.

MRI active guidewire with an embedded temperature probe and providing a distinct tip signal to enhance clinical safety.

BACKGROUND: The field of interventional cardiovascular MRI is hampered by the unavailability of active guidewires that are both safe and conspicuous. Heating of conductive guidewires is difficult to predict in vivo and disruptive to measure using external probes. We describe a clinical-grade 0.035" (0.89 mm) guidewire for MRI right and left heart catheterization at 1.5 T that has an internal probe to monitor temperature in real-time, and that has both tip and shaft visibility as well as suitable flexibility. METHODS: The design has an internal fiberoptic temperature probe, as well as a distal solenoid to enhance tip visibility on a loopless antenna. We tested different tip-solenoid configurations to balance heating and signal profiles. We tested mechanical performance in vitro and in vivo in comparison with a popular clinical nitinol guidewire. RESULTS: The solenoid displaced the point of maximal heating ("hot spot") from the tip to a more proximal location where it can be measured without impairing guidewire flexion. Probe pullback allowed creation of lengthwise guidewire temperature maps that allowed rapid evaluation of design prototypes. Distal-only solenoid attachment offered the best compromise between tip visibility and heating among design candidates. When fixed at the hot spot, the internal probe consistently reflected the maximum temperature compared external probes.Real-time temperature monitoring was performed during porcine left heart catheterization. Heating was negligible using normal operating parameters (flip angle, 45°; SAR, 1.01 W/kg); the temperature increased by 4.2°C only during high RF power mode (flip angle, 90°; SAR, 3.96 W/kg) and only when the guidewire was isolated from blood cooling effects by an introducer sheath. The tip flexibility and in vivo performance of the final guidewire design were similar to a popular commercial guidewire. CONCLUSIONS: We integrated a fiberoptic temperature probe inside a 0.035" MRI guidewire. Real-time monitoring helps detect deleterious heating during use, without impairing mechanical guidewire operation, and without impairing MRI visibility. We therefore need not rely on prediction to ensure safe clinical operation. Future implementations may modulate specific absorption rate (SAR) based on temperature feedback.

A deflectable guiding catheter for real-time MRI-guided interventions.

PURPOSE: To design a deflectable guiding catheter that omits long metallic components yet preserves mechanical properties to facilitate therapeutic interventional MRI procedures. MATERIALS AND METHODS: The catheter shaft incorporated Kevlar braiding. A 180° deflection was attained with a 5-cm nitinol slotted tube, a nitinol spring, and a Kevlar pull string. We tested three designs: passive, passive incorporating an inductively coupled coil, and active receiver. We characterized mechanical properties, MRI properties, RF induced heating, and in vivo performance in swine. RESULTS: Torque and tip deflection force were satisfactory. Representative procedures included hepatic and azygos vein access, laser cardiac septostomy, and atrial septal defect crossing. Visualization was best in the active configuration, delineating profile and tip orientation. The passive configuration could be used in tandem with an active guidewire to overcome its limited conspicuity. There was no RF-induced heating in all configurations under expected use conditions in vitro and in vivo. CONCLUSION: Kevlar and short nitinol component substitutions preserved mechanical properties. The active design offered the best visibility and usability but reintroduced metal conductors. We describe versatile deflectable guiding catheters with a 0.057" lumen for interventional MRI catheterization. Implementations are feasible using active, inductive, and passive visualization strategies to suit application requirements.

Direct percutaneous left ventricular access and port closure: pre-clinical feasibility.

OBJECTIVES: This study sought to evaluate feasibility of nonsurgical transthoracic catheter-based left ventricular (LV) access and closure. BACKGROUND: Implanting large devices, such as mitral or aortic valve prostheses, into the heart requires surgical exposure and repair. Reliable percutaneous direct transthoracic LV access and closure would allow new nonsurgical therapeutic procedures. METHODS: Percutaneous direct LV access was performed in 19 swine using real-time magnetic resonance imaging (MRI) and an "active" MRI needle antenna to deliver an 18-F introducer sheath. The LV access ports were closed percutaneously using a commercial ventricular septal defect occluder and an "active" MRI delivery cable for enhanced visibility. We used "permissive pericardial tamponade" (temporary fluid instillation to separate the 2 pericardial layers) to avoid pericardial entrapment by the epicardial disk. Techniques were developed in 8 animals, and 11 more were followed up to 3 months by MRI and histopathology. RESULTS: Imaging guidance allowed 18-F sheath access and closure with appropriate positioning of the occluder inside the transmyocardial tunnel. Of the survival cohort, immediate hemostasis was achieved in 8 of 11 patients. Failure modes included pericardial entrapment by the epicardial occluder disk (n = 2) and a true-apex entry site that prevented hemostatic apposition of the endocardial disk (n = 1). Reactive pericardial effusion (192 ± 118 ml) accumulated 5 ± 1 days after the procedure, requiring 1-time drainage. At 3 months, LV function was preserved, and the device was endothelialized. CONCLUSIONS: Direct percutaneous LV access and closure is feasible using real-time MRI. A commercial occluder achieved hemostasis without evident deleterious effects on the LV. Having established the concept, further clinical development of this approach appears realistic.

Closed-chest transthoracic magnetic resonance imaging-guided ventricular septal defect closure in swine.

OBJECTIVES: The aim of this study was to close ventricular septal defects (VSDs) directly through the chest wall using magnetic resonance imaging (MRI) guidance, without cardiopulmonary bypass, sternotomy, or radiation exposure. BACKGROUND: Surgical, percutaneous, and hybrid management of VSD each have limitations and known morbidity. METHODS: Percutaneous muscular VSDs were created in 10 naive Yorkshire swine using a transjugular laser catheter. Under real-time MRI guidance, a direct transthoracic vascular access sheath was introduced through the chest into the heart along a trajectory suitable for VSD access and closure. Through this transthoracic sheath, muscular VSDs were occluded using a commercial nitinol device. Finally, the right ventricular free wall was closed using a commercial collagen plug intended for arterial closure. RESULTS: Anterior, posterior, and mid-muscular VSDs (6.8 ± 1.8 mm) were created. VSDs were closed successfully in all animals. The transthoracic access sheath was displaced in 2, both fatal. Thereafter, we tested an intracameral retention sheath to prevent this complication. Right ventricular access ports were closed successfully in all, and after as many as 30 days, healed successfully. CONCLUSIONS: Real-time MRI guidance allowed closed-chest transthoracic perventricular muscular VSD closure in a clinically meaningful animal model. Once applied to patients, this approach may avoid traditional surgical, percutaneous, or open-chest transcatheter ("hybrid") risks.

Limitations of closing percutaneous transthoracic ventricular access ports using a commercial collagen vascular closure device.

INTRODUCTION: Closed-chest access and closure of direct cardiac punctures may enable a range of therapeutic procedures. We evaluate the safety and feasibility of closing percutaneous direct ventricular access sites using a commercial collagen-based femoral artery closure device. METHODS: Yorkshire swine underwent percutaneous transthoracic left ventricular access (n = 13). The access port was closed using a commercial collagen-based vascular closure device (Angio-Seal, St. Jude Medical) with or without prior separation of the pericardial layers by instillation of fluid into the pericardial space ("permissive pericardial tamponade"). After initial nonsurvival feasibility experiments (n = 6); animals underwent 1-week (n = 3) or 6-week follow-up (n = 4). RESULTS: In naïve animals, the collagen plug tended to deploy outside the parietal pericardium, where it failed to accomplish hemostasis. "Permissive pericardial tamponade" was created under MRI, and accomplished early hemostasis by allowing the collagen sponge to seat on the epicardial surface inside the pericardium. After successful closure, six of seven animals accumulated a large pericardial effusion 5 ± 1 days after closure. Despite percutaneous drainage during 6-week follow-up, the large pericardial effusion recurred in half, and was lethal in one. CONCLUSIONS: A commercial collagen-based vascular closure device may achieve temporary but not durable hemostasis when closing a direct left ventricular puncture port, but only after intentional pericardial separation. These insights may contribute to development of a superior device solution. Elective clinical application of this device to close apical access ports should be avoided.

Cardiac repolarization instability during normal postnatal development.

Long QT syndrome is a disease characterized by abnormal lengthening of the QT interval and by sudden cardiac death. It is a disease of development, with the incidence of a sudden event increasing during childhood. Repolarization instability during postnatal development could make the substrate susceptible to a fatal arrhythmia. Dynamic changes in repolarization that occur on a beat-to-beat basis, known as alternans, are a hallmark of electrical instability. T-wave alternans (TWA) in the electrocardiogram correlates with arrhythmia risk and long-term survival in adults. We determined TWA properties longitudinally in vivo in 7 propofol-sedated New Zealand white rabbits using transesophageal pacing weekly from 2 to 10 weeks of age. Furthermore, TWA induction after the onset of rapid pacing was characterized in vitro in 6 infant (2 weeks) and 6 adolescent (7 weeks) isolated, arterially perfused rabbit hearts. In vivo, TWA amplitude was maximum at 2 weeks and declined with age. Isoproterenol increased TWA at 8 weeks (adolescence). In vitro, large-amplitude TWA was induced with rapid pacing in both infant and adolescents but decreased to low, steady-state levels in infants. We conclude that TWA properties are age dependent in rabbit. Significant TWA is induced in rabbit at the onset of rapid pacing.

Treatment with an estrogen receptor-beta-selective agonist is cardioprotective.

This study was designed to investigate whether treatment with an estrogen receptor-beta (ER-beta)-selective agonist (2,3-bis(4-hydroxyphenyl)-propionitrile, DPN) can provide cardioprotection in female mice lacking endogenous estrogen. To study the effect of ER-beta stimulation in ischemia-reperfusion injury, we treated ovariectomized (ovx) female mice with 0.1 mg/kg/day of 17beta-estradiol, 0.8 mg/kg/day of DPN, or vehicle for 2 weeks. Isolated hearts were Langendorff perfused for 25 min prior to a 1-min treatment with isoproterenol, followed by 20 min of normothermic global ischemia and 40 min of reperfusion. Left ventricular developed pressure (LVDP) and heart rate were measured. Recovery of function at the end of 40 min of reperfusion was expressed as a percentage of pre-ischemic rate pressure product (RPP=LVDP x heart rate). Hearts from ovx female mice had a significantly lower recovery of LVDP than the hearts from intact female mice (12.4+/-1.6% vs. 19.6+/-1.6%, p<0.05, respectively). Furthermore, hearts from ovx female mice treated with DPN exhibited significantly better functional recovery than hearts from either vehicle-treated ovx female mice (20.1+/-2.2% vs. 12.4+/-1.6%, p<0.05, respectively) or wild type male mice (20.1+/-2.2% vs. 6.4+/-0.6%, p<0.05, respectively). DPN did not increase uterine weight in ovx females compared to vehicle treatment. Gene profiling showed that treatment with DPN resulted in upregulation of a number of protective genes such as heat shock protein 70, the antiapoptotic protein, growth arrest and DNA damage 45 beta, and cyclooxygenase 2.