Evaluation of Glutamine Utilization in Patients With Sickle Cell Disease.

Glutamine (Gln) was FDA-approved in 2017 to reduce acute sickle cell disease (SCD) pain and acute chest syndrome. However, typical pediatric patients with SCD exhibit moderate adherence, measured by a medication possession ratio <80%. This study examined Gln utilization in a "real-world" clinical setting to determine factors influencing medication adherence and to characterize the impact of an interdisciplinary team approach at an institution with specialty pharmacy services. A retrospective chart review identified 40 patients prescribed Gln by sickle cell specialists over a 2-year period and met selection criteria. Gln medication possession ratio for pediatric (72%) and adult (76%) patients were higher than other SCD medications. Pediatric patients (74%) demonstrated significantly lower first-attempt insurance approval rate compared with adult patients (95%) ( P =0.0026), suggesting an initial access barrier for pediatric patients. Pediatric patients demonstrated significantly higher number of medication fills (9.11 fills) compared with adult patients (3.86 fills) ( P =0.007), which suggests interdisciplinary collaboration may facilitate sustainable management of a new therapy. The majority of pediatric (89%) and adult (90%) patients reported high satisfaction with Gln ("excellent") with minor or no side effects. Multidisciplinary health care provider collaborations and tracking medication adherence metrics can help address barriers to care for SCD patients.

Human-centered design of clinical decision support for management of hypertension with chronic kidney disease.

BACKGROUND: Primary care providers face challenges in recognizing and controlling hypertension in patients with chronic kidney disease (CKD). Clinical decision support (CDS) has the potential to aid clinicians in identifying patients who could benefit from medication changes. This study designed an alert to control hypertension in CKD patients using an iterative human-centered design process. METHODS: In this study, we present a human-centered design process employing multiple methods for gathering user requirements and feedback on design and usability. Initially, we conducted contextual inquiry sessions to gather user requirements for the CDS. This was followed by group design sessions and one-on-one formative think-aloud sessions to validate requirements, obtain feedback on the design and layout, uncover usability issues, and validate changes. RESULTS: This study included 20 participants. The contextual inquiry produced 10 user requirements which influenced the initial alert design. The group design sessions revealed issues related to several themes, including recommendations and clinical content that did not match providers' expectations and extraneous information on the alerts that did not provide value. Findings from the individual think-aloud sessions revealed that participants disagreed with some recommended clinical actions, requested additional information, and had concerns about the placement in their workflow. Following each step, iterative changes were made to the alert content and design. DISCUSSION: This study showed that participation from users throughout the design process can lead to a better understanding of user requirements and optimal design, even within the constraints of an EHR alerting system. While raising awareness of design needs, it also revealed concerns related to workflow, understandability, and relevance. CONCLUSION: The human-centered design framework using multiple methods for CDS development informed the creation of an alert to assist in the treatment and recognition of hypertension in patients with CKD.

State of the art: Evaluation and prognostication of myocarditis using cardiac MRI.

Myocarditis encompasses both primary and secondary processes causing inflammation of the myocardium. Viral infections are a common secondary cause of myocarditis with important clinical relevance. Viral myocarditis has a varied clinical presentation, potentially resulting in significant morbidity and mortality. Acutely, systolic dysfunction and sudden cardiac death may ensue; chronically, myocarditis may result in a dilated cardiomyopathy requiring heart transplantation. Myocarditis is thought to be one of the most common causes of myocardial infarction with nonobstructive coronary arteries (MINOCA), with important consequences for cardiovascular outcomes. Patients with myocarditis are currently underdiagnosed. Cardiac MRI has evolved as the noninvasive test of choice, with cardiac MRI-specific diagnostic requirements defined in the Lake Louise Criteria (LLC). Detecting the presence of tissue edema, hyperemia, and necrosis in both acute and chronic stages form the foundation of the LLC. Cardiac MR for chronic myocarditis (greater than 8 weeks from symptom onset) has decreased sensitivity for diagnosis. Emerging sequences such as T1 and T2 parametric maps provide tissue characterization regarding inflammation without reliance on reference tissue, overcoming limitations of the LLC. Beyond diagnostic criteria, these imaging techniques have proven useful in further characterizing the diseased tissue, prognostication, and clinical decision-making. This review describes the utility and evolving use of cardiac MRI in clinical practice. Level of Evidence: 1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2018;47:1061-1071.

Sutureless repair of spontaneous coronary dissection with free wall rupture and cardiac tamponade.

Left ventricular free wall rupture is a feared complication of acute myocardial infarction typically presenting with cardiogenic shock. We present a case of spontaneous coronary artery dissection with free wall rupture and cardiac tamponade in an uncommon demographic. Friable myocardial tissue frequently precludes suture technique making biological glue repair a suitable option.

Three-dimensional echocardiography demonstrates a skewered left ventricular thrombus in a patient with a heart transplant.

A left ventricular (LV) false tendon is a frequently visualized structure in echocardiography with unclear clinical significance. We present the case of a false tendon serving as a nidus for thrombus in a post-orthotopic heart transplantation patient. Three-dimensional transthoracic echocardiography (3DTTE) was utilized to visualize a LV mass and facilitate its identification as a thrombus as well as the surrounding structures. Using datasets from 3DTTE, the lack of ventricular wall attachment and circumferential formation of the thrombus around the false tendon was identified. Serial imaging demonstrated resolution of the thrombus with anticoagulation.

Development of a Chest Wall Protector Effective in Preventing Sudden Cardiac Death by Chest Wall Impact (Commotio Cordis).

OBJECTIVE: Commotio cordis, sudden death with chest impact, occurs clinically despite chest wall protectors worn in sports. In an experimental model of commotio cordis, commercially available chest wall protectors failed to prevent ventricular fibrillation (VF). The goal of the current investigation was to develop a chest wall protector effective in the prevention of commotio cordis. DESIGN: In the Tufts experimental model of commotio cordis the ability of chest protectors to prevent VF was assessed. Impacts were delivered with a 40-mph lacrosse ball, timed to the vulnerable period for VF. INTERVENTION: A chest wall protector or no chest wall protector (control) was randomly assigned to be placed over the chest. Four iterative series of 2 to 4 different chest wall material combinations were assessed. Materials included 3 different foams (Accelleron [Unequal Technologies, Glen Mills, PA], closed cell high density foam; Airilon [Unequal Technologies, Glen Mills, PA], closed cell low density soft foam; and an open cell memory foam) that were adhered to a layer of TriDur (Unequal Technologies, Glen Mills, PA), a flexible elastomeric coated aramid that was bonded to a semirigid polypropylene polymer (ImpacShield, Unequal Technologies, Glen Mills, PA). MAIN OUTCOME MEASURE: Induction of VF by chest wall impact was the primary outcome. RESULTS: Of 80 impacts without chest protectors, 43 (54%) resulted in VF. Ventricular fibrillation with chest protectors ranged from a high of 60% to a low of 5%. Of 12 chest protectors assessed, only 3 significantly lowered the risk of VF compared with impacts without chest protectors. These 3 chest protectors were combinations of Accelleron, Airilon, TriDur, and ImpacShield of different thicknesses. Protection increased linearly with the thicker combinations. CONCLUSIONS: Effective protection against VF with chest wall protection can be achieved in an experimental model of commotio cordis. CLINICAL RELEVANCE: Chest protector designs incorporating these novel materials will likely be effective in the prevention of commotio cordis on the playing field.

Regional Analysis of Myocardial Strain to Wall Thickness Ratio in Cardiac Amyloidosis and Hypertrophic Cardiomyopathy.

BACKGROUND: Increased left ventricular wall thickness is a hallmark of cardiac amyloidosis (CA). Several other disease states, including hypertrophic cardiomyopathy (HCM), share this common feature. Myocardial strain has emerged as a diagnostic and prognostic tool to differentiate causes of increased left ventricular wall thickness. We sought to determine if regional strain differences were present in CA when compared with HCM when indexed to wall thickness as well as adjusting for important factors such as ejection fraction (EF), age, sex, and hypertension. METHODS: We performed a multicenter, retrospective analysis of 122 patients in 3 groups: CA (n=40), HCM (n=44), and controls (n=38). Using commercially available software, we determined peak systolic strain measurements in the base, mid, and apical segments in all 3 cardinal directions of radial strain, circumferential strain, and longitudinal strain. The regional strain was indexed to wall thickness to create a strain to wall thickness (STT) ratio. Analysis of Variance was performed to examine the association of each strain parameter with the disease group, adjusting for age, sex, hypertension, and EF. Multinomial logistic regression was performed to determine which combination of variables can potentially be used to best model the disease group. RESULTS: Ratios of STT at all 3 levels were significantly different with respect to the cardinal directions of radial, circumferential, and longitudinal strain in a multivariable analysis adjusting for age, sex, and hypertension. Specifically, with respect to the basal segments, the STT ratio across CA, HCM, and normal were significantly different in radial (1.13±0.34 vs. 3.79±0.22 vs. 4.12±0.38; P <0.0001), circumferential (-0.79±0.10 vs. -1.62±0.07 vs. -2.25±0.11; P <0.0001), and longitudinal directions (-0.41±0.09 vs. -1.03±0.06 vs. -1.41±0.10; P <0.0001). When adjusting for age, sex, hypertension and EF, only the base was significantly different between the CA and HCM groups in the radial (1.49±0.37 vs. 3.53±0.24; P <0.0001), circumferential -1.04±0.10 vs. -1.44±0.06; P <0.005), and longitudinal (-0.55±0.10 vs -0.94±0.06; P =0.007) directions. Using multinomial logistic regression, the use of age, left ventricular EF, global longitudinal strain, and basal radial strain yielded a diagnostic model with an area under the receiver operating characteristic curve (AUC) of 0.98. A model excluding age, despite being likely an independent predictor in our cohort, yielded an overall AUC of 0.90. When excluding age, the overall AUC was 0.91 and specifically when discriminating CA from HCM was 0.95. CONCLUSIONS: Regional myocardial strain indexed to wall thickness with an STT ratio can differentiate between etiologies of increased left ventricular wall thickness. Differences in myocardial deformation may be independent of wall thickness. Differences in basal strain when indexed to wall thickness in all 3 cardinal directions between CA and HCM are independent of EF. Multinomial logistic regression analysis using strain parameters differentiates CA and HCM with excellent diagnostic accuracy.

Clinical Decision Support for Hypertension Management in Chronic Kidney Disease: A Randomized Clinical Trial.

Importance: Chronic kidney disease (CKD) affects 37 million adults in the United States, and for patients with CKD, hypertension is a key risk factor for adverse outcomes, such as kidney failure, cardiovascular events, and death. Objective: To evaluate a computerized clinical decision support (CDS) system for the management of uncontrolled hypertension in patients with CKD. Design, Setting, and Participants: This multiclinic, randomized clinical trial randomized primary care practitioners (PCPs) at a primary care network, including 15 hospital-based, ambulatory, and community health center-based clinics, through a stratified, matched-pair randomization approach February 2021 to February 2022. All adult patients with a visit to a PCP in the last 2 years were eligible and those with evidence of CKD and hypertension were included. Intervention: The intervention consisted of a CDS system based on behavioral economic principles and human-centered design methods that delivered tailored, evidence-based recommendations, including initiation or titration of renin-angiotensin-aldosterone system inhibitors. The patients in the control group received usual care from PCPs with the CDS system operating in silent mode. Main Outcomes and Measures: The primary outcome was the change in mean systolic blood pressure (SBP) between baseline and 180 days compared between groups. The primary analysis was a repeated measures linear mixed model, using SBP at baseline, 90 days, and 180 days in an intention-to-treat repeated measures model to account for missing data. Secondary outcomes included blood pressure (BP) control and outcomes such as percentage of patients who received an action that aligned with the CDS recommendations. Results: The study included 174 PCPs and 2026 patients (mean [SD] age, 75.3 [0.3] years; 1223 [60.4%] female; mean [SD] SBP at baseline, 154.0 [14.3] mm Hg), with 87 PCPs and 1029 patients randomized to the intervention and 87 PCPs and 997 patients randomized to usual care. Overall, 1714 patients (84.6%) were treated for hypertension at baseline. There were 1623 patients (80.1%) with an SBP measurement at 180 days. From the linear mixed model, there was a statistically significant difference in mean SBP change in the intervention group compared with the usual care group (change, -14.6 [95% CI, -13.1 to -16.0] mm Hg vs -11.7 [-10.2 to -13.1] mm Hg; P = .005). There was no difference in the percentage of patients who achieved BP control in the intervention group compared with the control group (50.4% [95% CI, 46.5% to 54.3%] vs 47.1% [95% CI, 43.3% to 51.0%]). More patients received an action aligned with the CDS recommendations in the intervention group than in the usual care group (49.9% [95% CI, 45.1% to 54.8%] vs 34.6% [95% CI, 29.8% to 39.4%]; P < .001). Conclusions and Relevance: These findings suggest that implementing this computerized CDS system could lead to improved management of uncontrolled hypertension and potentially improved clinical outcomes at the population level for patients with CKD. Trial Registration: ClinicalTrials.gov Identifier: NCT03679247.

Defining the distance between the His bundle and first septal perforator: implications for left bundle branch pacing.

BACKGROUND: Left bundle branch pacing (LBBP) is a developing method of native conduction pacing, but cases of injury to the septal perforator arteries during implantation have been reported. Knowing the distance between the His bundle and the first septal perforator artery can help operators implant LBBP leads more safely. METHODS: Using previously performed coronary CT angiography (CCTA) studies, the distance between the His bundle and the first septal perforator was measured. RESULTS: A total of 50 CCTA studies were included. The mean distance from the His bundle to the first septal perforator (His-SP) along the line connecting the His bundle to the RV apex (His-RV apex) was 27.17 ± 7.7 mm with a range of 13.0 to 44.7 mm. The distance was greater than 2.0 cm in 84% of patients. To standardize this distance among patients with varying cardiac structures, the ratio between the His-SP distance and the His-RV Apex distance was also measured. The mean His-SP:His-RV Apex was 0.302 and the median was 0.298. Eighty-six percent of patients had a ratio of greater than 0.20. CONCLUSION: Using this information, operators can aim to implant LBBP leads within 2.0 cm of the His bundle or 20% of the distance between the His bundle and the RV apex with minimal risk of causing vascular injury.

Complications and Outcomes of Endovascular Embolization for Intractable Epistaxis: A Systematic Review and Meta-analysis.

OBJECTIVES: Endovascular embolization has emerged as an effective treatment for intractable epistaxis. This systematic review and meta-analysis aimed to calculate the rates of success, rebleeds, and complications and to identify the etiologies and complications of patients who undergo endovascular embolization. METHODS: This systematic review and meta-analysis was conducted per the guidelines set forth by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Articles were extracted from Scopus, PubMed, Web of Science, and Cochrane Central and were filtered by a systematic review process using Rayyan software. A random-effects model was used to quantify the rates success, rebleeds, and complications. RESULTS: Forty-two studies were included, totaling 1660 patients. The pooled success rate was 89% (95% confidence interval [CI] 86%-92%) and the pooled rebleed rate was 19% (95% CI 16%-22%). The pooled minor complication rate was 18% (95% CI 11%-27%). The most common major complication was soft tissue necrosis followed by stroke. The most common minor complication was facial pain. No minor complications were reported to be permanent. Of the patients who failed initial embolization, 42% underwent repeat embolization and 34% underwent surgical arterial ligation. CONCLUSIONS: Endovascular embolization is an effective treatment for intractable epistaxis. The decision to perform embolization should be carefully weighed given the rare but significant major complications.

Refining Clinical Phenotypes to Improve Clinical Decision Support and Reduce Alert Fatigue: A Feasibility Study.

BACKGROUND: Chronic kidney disease (CKD) is common and associated with adverse clinical outcomes. Most care for early CKD is provided in primary care, including hypertension (HTN) management. Computerized clinical decision support (CDS) can improve the quality of care for CKD but can also cause alert fatigue for primary care physicians (PCPs). Computable phenotypes (CPs) are algorithms to identify disease populations using, for example, specific laboratory data criteria. OBJECTIVES: Our objective was to determine the feasibility of implementation of CDS alerts by developing CPs and estimating potential alert burden. METHODS: We utilized clinical guidelines to develop a set of five CPs for patients with stage 3 to 4 CKD, uncontrolled HTN, and indications for initiation or titration of guideline-recommended antihypertensive agents. We then conducted an iterative data analytic process consisting of database queries, data validation, and subject matter expert discussion, to make iterative changes to the CPs. We estimated the potential alert burden to make final decisions about the scope of the CDS alerts. Specifically, the number of times that each alert could fire was limited to once per patient. RESULTS: In our primary care network, there were 239,339 encounters for 105,992 primary care patients between April 1, 2018 and April 1, 2019. Of these patients, 9,081 (8.6%) had stage 3 and 4 CKD. Almost half of the CKD patients, 4,191 patients, also had uncontrolled HTN. The majority of CKD patients were female, elderly, white, and English-speaking. We estimated that 5,369 alerts would fire if alerts were triggered multiple times per patient, with a mean number of alerts shown to each PCP ranging from 0.07-to 0.17 alerts per week. CONCLUSION: Development of CPs and estimation of alert burden allows researchers to iteratively fine-tune CDS prior to implementation. This method of assessment can help organizations balance the tradeoff between standardization of care and alert fatigue.

Contemporary cardiovascular computed tomography (CCT) training: Serial surveys of the international CCT community by the Fellow and Resident Leaders of the Society of Cardiovascular Computed Tomography (SCCT) Committee (FiRST) and SCCT Future Leaders Program (FLP).

BACKGROUND: As cardiovascular computed tomography (CCT) practice evolves, the demand for specialists continues to increase. However, CCT training remains variable globally with limited contemporaneous data to understand this heterogeneity. We sought to understand the role of CCT globally and the training available to underpin its use. METHODS: We performed two consecutive surveys of cardiology and radiology physicians, two years apart, utilizing the Society of Cardiovascular Computed Tomography (SCCT) website, weblinks, social media platforms, and meeting handouts to maximize our response rate. We compared United States (US)-based vs. international responses to understand global similarities and differences in practice and training in the surveys. RESULTS: 235 respondents (37% trainees and 63% educators/non-trainees) initiated the first survey with 174 (74%) completing the core survey, with 205 providing their work location (114 US and 91 international). Eighty-four percent (92/110) of educator respondents stated a need for increased training opportunities to meet growing demand. Dedicated training fellowships are heterogenous, with limited access to structural heart imaging training, despite structural scanning being performed within institutions. The lack of a standardized curriculum was identified as the main obstacle to effective CCT learning, particularly in the US, with web-based learning platforms being the most popular option for improving access to CCT training. 148 trainees initiated the second survey with 107 (72%) completing the core components (51% North America, 49% international). Only 68% said they would be able to meet their required CCT education needs via their training program. Obstacles in obtaining CCT training again included a lack of a developed curriculum (51%), a lack of dedicated training time (35%), and a lack of local faculty expertise (31%). There was regional variability in access to CCT training, and, in contrast to the first survey, most (89%) felt 1:1 live review of cases with trained/expert reader was most useful for improving CCT training alongside formal curriculum/live lectures (72%). CONCLUSIONS: There is a need to expand dedicated CCT training globally to meet the demand for complex CCT practice. Access to CCT education (didactic and 1:1 case-based teaching from expert faculty), implementation of recently published global training curricula, and increased teaching resources (web-based) as an adjunct to existing experiential learning opportunities, are all deemed necessary to address current educational shortfalls.

Combined Computed Tomography Angiography-Computed Tomography Perfusion in the Identification and Prognostic Assessment of Myocardial Bridging from the CORE320 Study: 5-Year Follow-Up.

Our objective is to use computed tomography angiography (CTA) and computed tomography perfusion (CTP) to identify the ischemic significance of myocardial bridging (MB). We also seek to determine the long-term prognostication of MB in the presence or absence of obstructive coronary artery disease (CAD). The CORE320, a prospective, multicenter study including 381 patients with known or suspected CAD clinically referred for invasive coronary angiography who underwent combined (CTA-CTP) and single-photon emission computed tomography before conventional coronary angiography. The incidence of MB was identified in 135 patients (35.4%) with 93.9% identified in the left anterior descending artery. MB were divided as partially encased versus fully encased. There was no difference in ischemia identified between partially encased MB and fully encased MB (37 [40%] vs 25 [35%], p = 0.54]. Ischemia was identified at similar rates in partially versus fully encased MB by single-photon emission computed tomography at (8 [9%] vs 8 [11%], p = 0.57] and CTP (34 [37%] vs 21 [30%], p = 0.33]. There was no difference in the primary outcome of 5-year outcome of combined incidence of myocardial infarction or death. The restricted mean survival time in patients with CTA with <50% stenosis with or without a MB was 4.906 years (95% confidence interval 4.759 to 5.000) and 4.891 years (95% confidence interval 4.718 to 5.000), respectively (p = 0.824). Cardiac computed tomography perfusion imaging can assess both anatomic and functional significance of myocardial bridging with diagnostic accuracy similar to current standard imaging. Furthermore, 5-year cardiovascular events were not different with the presence of MB in both obstructive and non-obstructive CAD.

Impact of Kidney Failure Risk Prediction Clinical Decision Support on Monitoring and Referral in Primary Care Management of CKD: A Randomized Pragmatic Clinical Trial.

Rationale & Objective: To design and implement clinical decision support incorporating a validated risk prediction estimate of kidney failure in primary care clinics and to evaluate the impact on stage-appropriate monitoring and referral. Study Design: Block-randomized, pragmatic clinical trial. Setting & Participants: Ten primary care clinics in the greater Boston area. Patients with stage 3-5 chronic kidney disease (CKD) were included. Patients were randomized within each primary care physician panel through a block randomization approach. The trial occurred between December 4, 2015, and December 3, 2016. Intervention: Point-of-care noninterruptive clinical decision support that delivered the 5-year kidney failure risk equation as well as recommendations for stage-appropriate monitoring and referral to nephrology. Outcomes: The primary outcome was as follows: Urine and serum laboratory monitoring test findings measured at one timepoint 6 months after the initial primary care visit and analyzed only in patients who had not undergone the recommended monitoring test in the preceding 12 months. The secondary outcome was nephrology referral in patients with a calculated kidney failure risk equation value of >10% measured at one timepoint 6 months after the initial primary care visit. Results: The clinical decision support application requested and processed 569,533 Continuity of Care Documents during the study period. Of these, 41,842 (7.3%) documents led to a diagnosis of stage 3, 4, or 5 CKD by the clinical decision support application. A total of 5,590 patients with stage 3, 4, or 5 CKD were randomized and included in the study. The link to the clinical decision support application was clicked 122 times by 57 primary care physicians. There was no association between the clinical decision support intervention and the primary outcome. There was a small but statistically significant difference in nephrology referral, with a higher rate of referral in the control arm. Limitations: Contamination within provider and clinic may have attenuated the impact of the intervention and may have biased the result toward null. Conclusions: The noninterruptive design of the clinical decision support was selected to prevent cognitive overload; however, the design led to a very low rate of use and ultimately did not improve stage-appropriate monitoring. Funding: Research reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under award K23DK097187. Trial Registration: ClinicalTrials.gov Identifier: NCT02990897.

Self-assembled enzymatic monolayer directly bound to a gold surface: activity and molecular recognition force spectroscopy studies.

Escherichia coli dihydrofolate reductase (ecDHFR) has one surface cysteine, C152, located opposite and distal to the active site. Here, we show that the enzyme spontaneously assembles on an ultraflat gold surface as a homogeneous, covalently bound monolayer. Surprisingly, the activity of the gold-immobilized ecDHFR as measured by radiographic analysis was found to be similar to that of the free enzyme in solution. Molecular recognition force spectroscopy was used to study the dissociation forces involved in the rupture of AFM probe-tethered methotrexate (MTX, a tight-binding inhibitor of DHFR) from the gold-immobilized enzyme. Treatment of the ecDHFR monolayer with free MTX diminished the interaction of the functionalized tip with the surface, suggesting that the interaction was indeed active-site specific. These findings demonstrate the viability of a simple and direct enzymatic surface-functionalization without the use of spacers, thus, opening the door to further applications in the area of biomacromolecular force spectroscopy.

Phenotypic variation and targeted therapy of hypertrophic cardiomyopathy using genetic animal models.

Hypertrophic cardiomyopathy (HCM) has a variable clinical presentation due to the diversity of causative genetic mutations. Animal models allow in vivo study of genotypic expression through non-invasive imaging, pathologic sampling, and force analysis. This review focuses on the spontaneous and induced mutations in various animal models affecting mainly sarcomere proteins. The sarcomere is comprised of thick (myosin) filaments and related proteins including myosin heavy chain and myosin binding protein-C; thin (actin) filament proteins and their associated regulators including tropomyosin, troponin I, troponin C, and troponin T. The regulatory milieu including transcription factors and cell signaling also play a significant role. Animal models provide a layered approach of understanding beginning with the causative mutation as a foundation. The functional consequences of protein energy utilization and calcium sensitivity in vivo and ex vivo can be studied. Beyond pathophysiologic disruption of sarcomere function, these models demonstrate the clinical sequalae of diastolic dysfunction, heart failure, and arrhythmogenic death. Through this cascade of understanding the mutation followed by their functional significance, targeted therapies have been developed and are briefly discussed.

The Longer the Block, the Harder You Fall: Extrinsic Idiopathic Atrioventricular Block Masquerading as Seizures.

History and physical examination are the diagnostic cornerstones of transient loss of consciousness (TLOC). However, details can be scarce and examination unrevealing, thus making the diagnosis elusive. In a case of convulsive TLOC, the initial diagnosis was incorrect, but a fortuitously captured event on telemetry yielded the diagnosis: extrinsic idiopathic atrioventricular block. (Level of Difficulty: Beginner.).

Low-molecular-weight chromium-binding substance (LMWCr) may bind and carry Cr(III) from the endosome.

Trivalent chromium has been proposed to be transported in vivo from the bloodstream to the tissues via endocytosis by transferrin (Tf), the major iron transport protein in the blood. While Cr(III) loss from the Tf/Tf receptor complex after acidification to pH 5.5 has recently been shown to be sufficiently rapid to be physiologically relevant, the released Cr(III) still must exit the endosome during the time of the endocytosis cycle (circa 15 min). Cr(III) binds too slowly to small ligands such as citrate or ascorbate, or even EDTA, for such complexes to form and be transported from the endosome, while no trivalent ion transporters are known. However, the apo form of the peptide low-molecular-weight chromium-binding substance (LMWCr) can remove Cr(III) from Cr(III)2-Tf at neutral pH, albeit slowly, and LMWCr is known to be transported from cells after binding Cr(III), although the transporter is not known. LMWCr subsequently carries Cr(III) to the bloodstream ultimately for removal from the body in the urine. The rate of binding of Cr(III) to apoLMWCr was significantly enhanced in the presence of the Tf/Tf receptor complex. These results suggest that apoLMWCr may function to bind Cr(III) released in the endosomes for ultimate removal from the body as part of a Cr(III) detoxification process.

An Anatomic Curiosity: A Sliver of a Liver in an Unusual Location.

A 48-year-old woman underwent preoperative cardiac testing prior to gastric bypass. She was incidentally found to have a right atrial mass on transthoracic echocardiography. Subsequent cardiac magnetic resonance confirmed this finding. She underwent excision of the mass. Tissue pathology revealed ectopic hepatic tissue. (Level of Difficulty: Advanced.).