Maturation of iPSC-derived cardiomyocytes in a heart-on-a-chip device enables modeling of dilated cardiomyopathy caused by R222Q-SCN5A mutation.

To better understand sodium channel (SCN5A)-related cardiomyopathies, we generated ventricular cardiomyocytes from induced pluripotent stem cells obtained from a dilated cardiomyopathy patient harbouring the R222Q mutation, which is only expressed in adult SCN5A isoforms. Because the adult SCN5A isoform was poorly expressed, without functional differences between R222Q and control in both embryoid bodies and cell sheet preparations (cultured for 29-35 days), we created heart-on-a-chip biowires which promote myocardial maturation. Indeed, biowires expressed primarily adult SCN5A with R222Q preparations displaying (arrhythmogenic) short action potentials, altered Na+ channel biophysical properties and lower contractility compared to corrected controls. Comprehensive RNA sequencing revealed differential gene regulation between R222Q and control biowires in cellular pathways related to sarcoplasmic reticulum and dystroglycan complex as well as biological processes related to calcium ion regulation and action potential. Additionally, R222Q biowires had marked reductions in actin expression accompanied by profound sarcoplasmic disarray, without differences in cell composition (fibroblast, endothelial cells, and cardiomyocytes) compared to corrected biowires. In conclusion, we demonstrate that in addition to altering cardiac electrophysiology and Na+ current, the R222Q mutation also causes profound sarcomere disruptions and mechanical destabilization. Possible mechanisms for these observations are discussed.

Integrated vascular surgery applicants' perspectives of virtual residency interviews during the coronavirus disease 2019 application cycle.

BACKGROUND: In agreement with Association of American Medical Colleges guidelines, the 2020 to 2021 integrated vascular surgery (I-VS) residency interviews were conducted virtually. In the present study, we collected data about the virtual interview process from the applicant's perspective, including preferences for interview format and the virtual resources they found most helpful. METHODS: An anonymous, online survey study of medical students who had been accepted into I-VS residencies during the 2020 to 2021 application cycle was performed. The survey contained questions about applicant behavior during the virtual application cycle, their perception of the virtual interviews, the utility of the virtual format, their preferences, and the virtual resources they found the most helpful for determining their rank list. RESULTS: Of 72 applicants, 38 (18 women, 19 men, and 1 declined to answer) had completed the survey for a 57.2% response rate. The average number of programs interviewed was 25 to 30 (31%). More than one-half (55%) of the respondents had responded that they had interviewed at more programs than they would have had the interviews been in person. More than one-half of the applicants (55%) reported that they preferred remote interviews with the option to visit in-person at their top choice programs compared with the use of all remote interviews (21%) or all in-person interviews (18%). Most had somewhat or strongly agreed (79%) that virtual interviews allowed them to properly gauge a residency program and provided adequate opportunities to interact with the residents (65%). The online resources the applicants found the most helpful in determining their rank lists were attending educational conferences, prerecorded videos from faculty and residents, and the program's social media platforms. CONCLUSIONS: The results from the present study have illuminated the current trends and attitudes of I-VS applicants for virtual interviews, including the virtual resources they found the most useful. Virtual interviews were a preferred method of interviewing and allowed applicants to assess a residency program and interact with the current residents. These variables should be considered by the program leadership when developing protocols for upcoming application cycles.

"Diffusion of innovations": a feasibility study on the pericapsular nerve group block in the emergency department for hip fractures.

OBJECTIVE: Hip fractures are associated with significant morbidity and mortality. Ultrasound-guided peripheral nerve blocks are a safe method to manage pain and decrease opioid usage. The pericapsular nerve group (PENG) block is a novel, potentially superior block because of its motor-sparing effects. Through training, simulation, and supervision, we aim to determine whether it is feasible to perform the PENG block in the emergency department. METHODS: Phase 1 consisted of emergency physicians attending a workshop to demonstrate ultrasound proficiency, anatomical understanding, and procedural competency using a low-fidelity model. Phase 2 consisted of a prospective, observational, feasibility study of 10 patients with hip fractures. Pain scores, side effects, and opioid usage data were collected. RESULTS: The median pain score at time 0 (time of block) was 9 (interquartile range [IQR], 6.5-9). The median pain score at 30 minutes was 4 (IQR, 2.0-6.8) and 3.5 (IQR, 1.0-4.8) at 4 hours. All 10 patients required narcotics prior to the initiation of the PENG block with a median dosage of 6.25 morphine milligram equivalents (MME; IQR, 4.25-7.38 MME). After the PENG block, only 30% of the patients required further narcotics with a median dosage of 0 MME (IQR, 0-0.6 MME) until operative fixation. CONCLUSION: In this feasibility study, PENG blocks were safely administered by trained emergency physicians under supervision. We demonstrated data suggesting a trend of pain relief and decreased opiate requirements, and further investigation is necessary to measure efficacy.

Multi-Axes Lead With Tetrahedral Electrode Tip for Cardiac-Implantable Devices: Creative Concept for Pacing and Sensing Technology.

BACKGROUND: We developed a multi-axes lead (MaxLead) incorporating 4 electrodes arranged at the lead-tip, organized in an equidistant tetrahedron. Here, we studied MaxLead performance in sensing, pacing, and activation wavefront-direction analysis. METHODS: Sixteen explanted animal hearts (from 7 pigs, 7 sheep, and 2 rabbits) were used. Pacing threshold was tested from all axes of MaxLead from right-ventricular (RV) apex before and after simulated dislodgement. In addition, conduction-system pacing was performed in sheep heart preparations from all axes of MaxLead. Sensing via MaxLead positioned at RV apex was tested during sinus rhythm (SR), pacing from RV and left-ventricular (LV) free-wall, and ventricular fibrillation (VF). MaxLead-enabled voltage (MaxV), defined as the largest span of the sensed electric field loop, was compared with traditional lead-tip voltage detection. RESULTS: Pacing: MaxLead minimized change in pacing threshold owing to lead dislodgement (average voltage change 0.2 mV; 95% confidence interval [CI], -0.5 to 0.9), using multiple bipoles available for pacing. In animals with high conduction system-pacing thresholds (> 2 mV) in 1 or more bipoles (3 of 7), acceptable thresholds (< 1 mV) were demonstrated in an average of 2.5 remaining bipoles. Sensing: MaxV of SR and VF was consistently higher than the highest bipolar voltage (voltage difference averaged -0.18 mV, 95% CI, -0.28 to -0.07), P = 0.001). Electric field-loop geometry consistently differentiated ventricular activation in SR from that during pacing from RV and LV free walls. CONCLUSIONS: The multi-axes MaxLead electrode showed advantages in pacing, sensing, and mapping and has the potential to allow for improvements in lead-electrode technology for cardiac-implanted electronic devices.

The Impact of a Mobile Phone Application for Retention of Bleeding Control Skills.

BACKGROUND: The American College of Surgeons Bleeding Control Course (B-Con) empowers bystanders with hemorrhage control skills to manage prehospital emergencies, but demonstrates poor skill retention. The point of care use of a free Stop the Bleed mobile phone application on the retention of hemorrhage control skills from the B-Con Course was explored. METHODS: Convenience sample of college students previously trained in B-Con were randomized into mobile application (MA) or control groups. The use of a mobile application during a simulated emergency scenario with tourniquet and situational awareness skills was assessed. Wound packing skill retention without intervention was also assessed. Survey data allowed for comparison of participant perceptions of skills with actual performances. RESULTS: MA (n = 30) was superior to control (n = 32) in correct tourniquet application (62.5% versus 30.0%; P = 0.01) with longer placement times (163 sec versus 95 sec; P < 0.001) and in calling 911 (31.3% versus 3.3%, P = 0.004). Participants maintain inflated perceptions of their skills, but generally feel underprepared for a future bleeding emergency. CONCLUSIONS: Mobile apps improve tourniquet and situational awareness skills and may serve as potential aids to improve bystander hemorrhage control skills in real-time, but require further prospective investigation into its use.

Safety, efficacy, and monitoring of bipolar radiofrequency ablation in beating myopathic human and healthy swine hearts.

BACKGROUND: The safety and efficacy parameters for bipolar radiofrequency (RF) ablation are not well defined. OBJECTIVE: The purpose of this study was to investigate the safe range of power, utility of transmyocardial bipolar electrogram (EGM) amplitude, and circuit impedance in ablation monitoring. METHODS: Sixteen beating ex vivo human and swine hearts were studied in a Langendorff setup. Ninety-two bipolar ablations using two 4-mm irrigated catheters were performed at settings of 20-50 W, 60 seconds, and 30 mL/min irrigation in the left ventricle. RESULTS: For low-power ablations (20 and 30 W), transmurality was observed in 29 of 38 (76%) and 10 of 28 (36%) ablations for tissue thickness ≤17 mm and >17 mm, respectively. For high-power ablations (40 and 50 W), transmurality was observed in 5 of 7 (71%) and 7 of 19 (37%) ablations for tissue thickness ≤17 mm and >17 mm, respectively. Steam pop occurrence for low- and high-power ablations was 11 of 66 (16%) and 16 of 26 (62%), respectively (P = .0001), respectively. Lesion depth (limited by transmurality) was 12.0 ± 5.7 mm and 12.3 ± 5.8 mm, respectively (P = 1). Transmyocardial EGM amplitude decrement >60% strongly predicted transmurality (area under the curve [AUC] 0.8), and circuit impedance decrement >26% predicted steam pops (AUC 0.75). Half-normal saline did not affect transmurality or incidence of steam pops compared to normal saline irrigation. CONCLUSION: Bipolar RF ablation at power of 20-30 W provided an ideal balance of safety and efficacy, whereas power ≥40 W should be used with caution due to the high incidence of steam pops. Lesion transmurality monitoring and steam pop avoidance were best achieved using transmyocardial bipolar EGM voltage and circuit impedance, respectively.

A 3-D human model of complex cardiac arrhythmias.

Cardiac arrhythmias impact over 12 million people globally, with an increasing incidence of acquired arrhythmias. Although animal models have shed light onto fundamental arrhythmic mechanisms, species-specific differences and ethical concerns remain. Current human models using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) either lack the higher order tissue organization of the heart or implement unreliable arrhythmia induction techniques. Our goal was to develop a robust model of acquired arrhythmia by disrupting cardiomyocyte cell-cell signaling - one of the hallmarks of complex arrhythmias. Human 3D microtissues were generated by seeding hydrogel-embedded hiPSC-CMs and cardiac fibroblasts into an established microwell system designed to enable active and passive force assessment. Cell-cell signaling was disrupted using methyl-beta cyclodextrin (MBCD), previously shown to disassemble cardiac gap junctions. We demonstrate that arrhythmias were progressive and present in all microtissues within 5 days of treatment. Arrhythmic tissues exhibited reduced conduction velocity, an increased number of distinct action potentials, and reduced action potential cycle length. Arrhythmic tissues also showed significant reduction in contractile force generation, increased beating frequency, and increased passive tension and collagen deposition, in line with fibrosis. A subset of tissues with more complex arrhythmias exhibited 3D spatial differences in action potential propagation. Pharmacological and electrical defibrillation was successful. Transcriptomic data indicated an enrichment of genes consistent with cardiac arrhythmias. MBCD removal reversed the arrhythmic phenotype, resulting in synchronicity despite not resolving fibrosis. This innovative & reliable human-relevant 3D acquired arrhythmia model shows potential for improving our understanding of arrhythmic action potential conduction and furthering therapeutic development. STATEMENT OF SIGNIFICANCE: This work describes a 3D human model of cardiac arrhythmia-on-a-chip with high reproducibility, fidelity, and extensive functional applicability. To mimic in vivo conditions, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and cardiac fibroblasts from healthy controls were combined in a biocompatible fibrin hydrogel and seeded between two deflectable polymeric rods. Using the innate functional properties of this 3D model as well as advanced optical imaging techniques we demonstrated dramatic changes in contraction rate, synchronicity, and electrophysiological conduction in arrhythmic tissues relative to controls. Taken together, these data demonstrate the distinctive potential of this new model for pathophysiological studies, and for arrhythmia drug testing applications.

Analysis of electrooculography signals for the detection of Myasthenia Gravis.

OBJECTIVE: A precursor to more severe forms of Myasthenia Gravis (MG) is ocular MG (OMG) in which the MG symptoms are localized to the eyes. Current MG diagnostic methods are often invasive, painful, and not always specific. The objective of the proposed work was to extract quantifiable features from electrooculography (EOG) signals recorded around the eyes and develop an alternative non-invasive screening method for detecting MG. METHODS: EOG signals acquired from MG and Control subjects were analyzed for eye movement characteristics and quantified using time and wavelet domain signal processing techniques. The ability of the proposed approaches to classify MG vs. control subjects was evaluated using a linear discriminant analysis (LDA) based classifier. RESULTS: The range of overall classification accuracies achieved by the proposed time and wavelet domain approaches for different groupings were between 82.1-83.3% (Rise Rate feature: P < 0.01, AUC ≥ 0.87) and 82.1-87.2% (Mean Scale Band Energy feature: P < 0.01, AUC ≥ 0.89), respectively. CONCLUSION: Our results demonstrate that an EOG-based signal analysis is a potentially viable non-invasive alternative for MG screening. SIGNIFICANCE: The proposed approach could lead to early detection of MG and thereby improve clinical outcomes in this population.

Exit sites on the epicardium rarely subtend critical diastolic path of ischemic VT on the endocardium: Implications for noninvasive ablation.

BACKGROUND: Noninvasive electrocardiographic mapping of ventricular tachycardia (VT) and ablation using stereotactic radiotherapy was recently reported. This strategy does not directly evaluate the critical diastolic components and assumes that the epicardial exit site of VT subtends closely over the endocardial mid-diastolic isthmus. OBJECTIVE: To determine if the epicardial exit site of VT spatially corresponds to the critical diastolic components of ischemic scar-related VT. MATERIALS AND METHODS: Intraoperative simultaneous endocardial and epicardial mapping were performed during VT using a 112-bipole endocardial balloon and 112-bipole epicardial sock array. In eight patients, nine VTs having entire diastolic circuit mapped were included in the study. The diastolic path and VT-exit sites (epicardial and endocardial) were determined. RESULTS: The diastolic path was mapped in the endocardium for all nine VTs (median length, 50; interquartile range [IQR], 28 mm). The tachycardia cycle length ranged from 210-500 ms. The VT-exit site was early in the endocardium for six VTs and on the epicardium for three VTs. The mid-diastolic isthmus and endocardial exit site of the six endocardial VTs were spatially distant from their epicardial exit site by a median distance of 32 and 27 mm, respectively. For the three VTs with an early epicardial exit, the isthmus and endocardial exit sites were distant from the epicardial exit site by a median distance of 34 and 38 mm, respectively. CONCLUSION: The epicardial exit site and the mid-diastolic isthmus sites were spatially distant and discrepant. Surface electrocardiography (ECG)-derived strategy in identifying epicardial exit site to select noninvasive ablation targets is prone to identify epicardial exit sites and may not identify critical targets in ischemic scar VT.

Information theory to tachycardia therapy: electrogram entropy predicts diastolic microstructure of reentrant ventricular tachycardia.

There is no known strategy to differentiate which multicomponent electrograms in sinus rhythm maintain reentrant ventricular tachycardia (VT). Low entropy in the voltage breakdown of a multicomponent electrogram can localize conditions suitable for reentry but has not been validated against the classic VT activation mapping. We examined whether low entropy in a late and diversely activated ventricular scar region characterizes and differentiates the diastolic path of VT and represents protected tissue channels devoid of side branches. Intraoperative bipolar electrogram (BiEGM) activation and entropy maps were obtained during sinus rhythm in 17 patients with ischemic cardiomyopathy and compared with diastolic activation paths of VT (total of 39 VTs). Mathematical modeling of a zigzag main channel with side branches was also used to further validate structural representation of low entropy in the ventricular scar. A median of one region per patient (range: 1-2 regions) was identified in sinus rhythm, in which BiEGM with the latest mean activation time and adjacent minimum entropy were assembled together in a high-activation dispersion region. These regions accurately recognized diastolic paths of 34 VTs, often to multiple inducible VTs within a single individual arrhythmogenic region. In mathematical modeling, side branching from the main channel had a strong influence on the BiEGM composition along the main channel. The BiEGM obtained from a long unbranched channel had the lowest entropy compared with those with multiple side branches. In conclusion, among a population of multicomponent sinus electrograms, those that demonstrate low entropy and are delayed colocalize to critical long-protected channels of VT. This information is pertinent for planning VT ablation in sinus rhythm. NEW & NOTEWORTHY Entropy is a measure to quantify breakdown in information. Electrograms from a protected tissue channel can only possess a few states in their voltage and thus less information. In contrast, current-load interactions from side branches in unprotected channels introduce a number of dissimilar voltage deflections and thus high information. We compare here a mapping approach based on entropy against a rigorous reference standard of activation mapping during VT and entropy was assessed in sinus rhythm.