Wnt Signaling Interactor WTIP (Wilms Tumor Interacting Protein) Underlies Novel Mechanism for Cardiac Hypertrophy

BACKGROUND

The study of hypertrophic cardiomyopathy (HCM) can yield insight into the mechanisms underlying the complex trait of cardiac hypertrophy. To date, most genetic variants associated with HCM have been found in sarcomeric genes. Here, we describe a novel HCM-associated variant in the noncanonical Wnt signaling interactor WTIP (Wilms tumor interacting protein) and provide evidence of a role for WTIP in complex disease.

METHODS

In a family affected by HCM, we used exome sequencing and identity-by-descent analysis to identify a novel variant in WTIP (p.Y233F). We knocked down WTIP in isolated neonatal rat ventricular myocytes with lentivirally delivered short hairpin ribonucleic acids and in Danio rerio via morpholino injection. We performed weighted gene coexpression network analysis for WTIP in human cardiac tissue, as well as association analysis for WTIP variation and left ventricular hypertrophy. Finally, we generated induced pluripotent stem cell-derived cardiomyocytes from patient tissue, characterized size and calcium cycling, and determined the effect of verapamil treatment on calcium dynamics.

RESULTS

WTIP knockdown caused hypertrophy in neonatal rat ventricular myocytes and increased cardiac hypertrophy, peak calcium, and resting calcium in D rerio. Network analysis of human cardiac tissue indicated WTIP as a central coordinator of prohypertrophic networks, while common variation at the WTIP locus was associated with human left ventricular hypertrophy. Patient-derived WTIP p.Y233F-induced pluripotent stem cell-derived cardiomyocytes recapitulated cellular hypertrophy and increased resting calcium, which was ameliorated by verapamil.

CONCLUSIONS

We demonstrate that a novel genetic variant found in a family with HCM disrupts binding to a known Wnt signaling protein, misregulating cardiomyocyte calcium dynamics. Further, in orthogonal model systems, we show that expression of the gene WTIP is important in complex cardiac hypertrophy phenotypes. These findings, derived from the observation of a rare Mendelian disease variant, uncover a novel disease mechanism with implications across diverse forms of cardiac hypertrophy.

Clinical impact of acquired risk factors in TTN-mediated dilated cardiomyopathy

Background/Introduction

Truncating variants in TTN-encoded titin (TTNtvs) underlie ∼25% of familial dilated cardiomyopathy (DCM) cases. In addition, TTNtvs are over-represented in alcoholic, peripartum, and chemotherapy-induced CM suggesting that risk factors may play a substantive role in the penetrance and expressivity of TTN-mediated DCM.

Purpose

To determine the prevalence and clinical impact of risk factors for TTN-mediated DCM within a single center cohort of unrelated patients with pathogenic (P)/likely pathogenic (LP) TTNtvs.

Methods

In this retrospective study, an institutionally developed natural language processing algorithm was used to identify all TTNtv-positive patients evaluated clinically between 01/2012 and 12/2019. Each TTNtv was then mapped to the TTN reference sequence (NM_133378.4) and classified according to a strict interpretation of the 2015 American College of Medical Genetics and Genomics (ACMG) guidelines. After exclusion of individuals with complex congenital heart disease, ischemic heart disease, and those without ACMG P/LP TTNtvs, available medical records were reviewed for risk factors such as long-term heavy alcohol consumption (>80 grams/day), cardiotoxic chemotherapy exposure, morbid obesity (body mass index >40), biopsy/imaging-confirmed myocarditis, peripartum/tachycardia-mediated CM, and valvular heart disease.

Results

Overall, 33 ACMG P/LP TTNtv-positive patients were identified (40% female; mean age at presentation 45±16 years; mean LVEF at presentation 38%±17%). Of note, 17/33 (52%) presented with heart failure (HF) and 4/33 (12%) presented with sustained ventricular arrhythmias (VAs). The remaining 12 (36%) TTNtv-positive patients presented with incidentally detected asymptomatic left ventricular systolic dysfunction (n=9) or as a result of genetic cascade screening (n=3). In comparison to TTNtv-positive patients with non-HF presentations, those with HF had worse left ventricular function (mean LVEF: 26% ± 11% vs 51% ±12%; p<0.001) and were more likely to have ≥1 risk factor [11/17 (65%) vs 4/16 (25%); p=0.04]. Unexpectedly, the 7 TTNtv-positive patients that presented with (n=4) or subsequently developed (n=3) sustained VAs were younger at the time of presentation (34±13 years vs 48±15 years; p=0.04) and displayed a similar degree of left ventricular dysfunction to those without sustained VAs (mean LVEF: 42% ± 17% vs 36% ± 17%; p=ns). Interestingly, the only risk factor over-represented amongst those with sustained VAs was bileaflet mitral valve prolapse [3/7 (43%) vs 0/26 (0%); p=0.006].

Conclusion

The majority of TTNtv-positive patients (14/23; 61%) with a history of HF and/or sustained VAs possessed ≥1 acquired risk factor providing further evidence that gene-environment interaction(s) exert a crucial role in the manifestation of TTN-mediated disease.

Funding Acknowledgement

Type of funding source: None

P4172Prevalence and potential genetic determinants of young sudden unexplained death victims with suspected arrhythmogenic mitral valve prolapse

Background

Mitral valve prolapse (MVP) is largely considered a benign condition. Recently, arrhythmogenic MVP, a sudden cardiac death (SCD)-predisposing condition characterized clinically by frequent/complex ventricular arrhythmias likely secondary to prolapsing leaflet-induced fibrosis of the left ventricle (LV), has emerged as an underappreciated cause of sudden unexplained death in the young (SUDY).

Objective

To determine the prevalence and potential genetic underpinnings of suspected arrhythmogenic MVP in a referral cohort of SUDY cases.

Methods

In this retrospective necropsy study, the medical records, autopsy reports, and whole exome molecular autopsy (WEMA) results for 77 SUDY victims (27 females; average age at death 20.6±8.9 years) were reviewed. Evidence of myxomatous MVP and concomitant LV pathology were noted. Variants detected in the pre-specified 164 WEMA gene panel with a frequency <0.001 in public exomes were classified using the 2015 American College of Medical Genetics (ACMG) guidelines.

Results

Overall, 6/77 (7.8%; 2 females; average age at death 20.7±6.9 years) SUDY cases had MVP as the lone abnormal post-mortem finding. The majority had bileaflet involvement (5/6; 83%) and microscopic LV fibrosis (5/6; 83%). Two SUDY cases (33%) were diagnosed with MVP by echocardiography prior to death. No gross hypertrophy, myocyte disarray, or fibrofatty replacement was noted. Unexpectedly, an ACMG pathogenic/likely pathogenic (P/LP) was more likely to be detected in SUDY cases with MVP than those without [3/6 (50%) vs 9/71 (13%); p<0.05]. Interestingly, the three variants identified in MVP-positive SUDY cases localized to genes associated previously with a cardiomyopathy/channelopathy predisposition (p.E1518fsX25-DMD, p.S285N-RYR2, and p.R109X-TTN).

Conclusion

This WEMA series provides additional evidence that the combination of bileaflet MVP and microscopic LV fibrosis underlies an unexpected number of SUDY cases. Whether P/LP variants in cardiomyopathy/channelopathy-susceptibility genes function as contributing factors or if unrelated, but poorly understood, molecular mechanisms account for the distinct cardiomyopathy-like phenotype observed in arrhythmogenic MVP requires further investigation.

New Media in Medical Education

ln 1984 the American Association of Medical Colleges´ Panel on the General Professional Education of the Physician challenged the medical community to take a leadership position in the effective application of information science and computer technology to medical education. The medical education community has risen to that challenge through the use of microcomputer technology and optical disc media including the recently developed fully integrated Hypermedia environment to enhance the learning environment.

Patient and Provider Satisfaction with Teledermatology

BACKGROUND

There is little research comparing dermatologist and patient satisfaction with in-person, store-and-forward, and live interactive examinations.

OBJECTIVE

To compare satisfaction with in-person examinations to store-and-forward and live interactive consultations having two types of video.

METHODS

A controlled study was conducted where patients referred for dermatology consultations were examined in-person, by video, and by store-and-forward methods. Video changed between compressed and uncompressed on alternate clinics. Patients and dermatologists rated encounters after each examination. Dermatologists doing store-and-forward evaluations rated the quality of information provided. After experiencing all methods patients ranked their preferences. Dermatologists ranked their preferences at the end of the study.

RESULTS

In-person examinations were preferred by both patients and dermatologists. Overall, satisfaction with teledermatology was still high. Patients were evenly divided in preferring store-and-forward workups or live interactive video. Dermatologists were also divided on store-and-forward and uncompressed video, but tended toward the latter. Compressed video was the least preferred method among dermatologists.

LIMITATIONS

Dermatology residents took store-and-forward photos and their quality was likely superior to those normally taken in practice.

CONCLUSIONS

Patients and dermatologists prefer in-person examinations and diverge on preferring store-and-forward and live interactive when video is not compressed. The amount of video compression that can be applied without noticeable image degradation is a question for future research.

Comparing High Definition Live Interactive and Store-and-Forward Consultations to In-Person Examinations

BACKGROUND

There is little teledermatology research directly comparing remote methods, even less research with two in-person dermatologist agreement providing a baseline for comparing remote methods, and no research using high definition video as a live interactive method.

OBJECTIVE

To compare in-person consultations with store-and-forward and live interactive methods, the latter having two levels of image quality.

METHODS

A controlled study was conducted where patients were examined in-person, by high definition video, and by store-and-forward methods. The order patients experienced methods and residents assigned methods rotated, although an attending always saw patients in-person. The type of high definition video employed, lower resolution compressed or higher resolution uncompressed, was alternated between clinics. Primary and differential diagnoses, biopsy recommendations, and diagnostic and biopsy confidence ratings were recorded.

RESULTS

Concordance and confidence were significantly better for in-person versus remote methods and biopsy recommendations were lower. Store-and-forward and higher resolution uncompressed video results were similar and better than those for lower resolution compressed video.

LIMITATIONS

Dermatology residents took store-and-forward photos and their quality was likely superior to those normally taken in practice. There were variations in expertise between the attending and second and third year residents.

CONCLUSION

The superiority of in-person consultations suggests the tendencies to order more biopsies or still see patients in-person are often justified in teledermatology and that high resolution uncompressed video can close the resolution gap between store-and-forward and live interactive methods.

Sudden Cardiac Death in the Young

Although the occurrence of sudden cardiac death (SCD) in a young person is a rare event, it is traumatic and often widely publicized. In recent years, SCD in this population has been increasingly seen as a public health and safety issue. This review presents current knowledge relevant to the epidemiology of SCD and to strategies for prevention, resuscitation, and identification of those at greatest risk. Areas of active research and controversy include the development of best practices in screening, risk stratification approaches and postmortem evaluation, and identification of modifiable barriers to providing better outcomes after resuscitation of young SCD patients. Institution of a national registry of SCD in the young will provide data that will help to answer these questions.

Mobile Videoconferencing Apps for Telemedicine

INTRODUCTION

The quality and performance of several videoconferencing applications (apps) tested on iOS (Apple, Cupertino, CA) and Android (Google, Mountain View, CA) mobile platforms using Wi-Fi (802.11), third-generation (3G), and fourth-generation (4G) cellular networks are described.

MATERIALS AND METHODS

The tests were done to determine how well apps perform compared with videoconferencing software installed on computers or with more traditional videoconferencing using dedicated hardware. The rationale for app assessment and the testing methodology are described.

RESULTS

Findings are discussed in relation to operating system platform (iOS or Android) for which the apps were designed and the type of network (Wi-Fi, 3G, or 4G) used. The platform, network, and apps interact, and it is impossible to discuss videoconferencing experienced on mobile devices in relation to one of these factors without referencing the others.

CONCLUSIONS

Apps for mobile devices can vary significantly from other videoconferencing software or hardware. App performance increased over the testing period due to improvements in network infrastructure and how apps manage bandwidth.

Lessons learned from ten years of distance learning outreach

OBJECTIVE

The study tested the efficacy of providing distance learning with real-time videoconferencing to broaden high school student knowledge of health careers.

METHODS

A pilot program was tried out and extended over ten years to include other schools in four different time zones and the National Library of Medicine. Survey results, site visits, and continued school participation were used as effectiveness indicators. Student ratings, site visits, and ongoing discussions were used to evaluate critical factors in the program.

RESULTS

Nine program factors contributed to success.

CONCLUSIONS

Synchronous communication can be effective for outreach to special populations given appropriate infrastructure, technology, program design, and implementation.

Cloud and traditional videoconferencing technology for telemedicine and distance learning

INTRODUCTION

Cloud-based videoconferencing versus traditional systems are described for possible use in telemedicine and distance learning.

MATERIALS AND METHODS

Differences between traditional and cloud-based videoconferencing systems are examined, and the methods for identifying and testing systems are explained. Findings are presented characterizing the cloud conferencing genre and its attributes versus traditional H.323 conferencing.

RESULTS

Because the technology is rapidly evolving and needs to be evaluated in reference to local needs, it is strongly recommended that this or other reviews not be considered substitutes for personal hands-on experience.

CONCLUSIONS

This review identifies key attributes of the technology that can be used to appraise the relevance of cloud conferencing technology and to determine whether migration from traditional technology to a cloud environment is warranted. An evaluation template is provided for assessing systems appropriateness.

Uncompressed high-definition videoconferencing tools for telemedicine and distance learning

Uncompressed high-definition (HD) video image quality is superior to compressed HD video provided in most commercially available videoconferencing products. Uncompressed HD videoconferencing tools provide a more immersive experience because there is no reduction of image information and, in most cases, lower latency. Four open source uncompressed video applications are reviewed that have been tested at the National Library of Medicine: three transmitting uncompressed HD video and one transmitting loosely compressed standard-definition video. The technical requirements for implementing each are described, and test results in terms of image quality, latency, and application reliability are presented. Because the hardware and bandwidth requirements for uncompressed HD video are relatively high and most applications are still under development, they are generally not ready for mass deployment. Some are, however, ready for pilot testing and experimentation in clinical settings by either those who have or anticipate having bandwidth sufficient to support them or those interested in researching the effects higher-quality video may have on diagnostic and other clinical outcomes.

Safety of Sports for Athletes With Implantable Cardioverter-Defibrillators

Background—

The risks of sports participation for implantable cardioverter-defibrillator (ICD) patients are unknown.

Methods and Results—

Athletes with ICDs (age, 10–60 years) participating in organized (n=328) or high-risk (n=44) sports were recruited. Sports-related and clinical data were obtained by phone interview and medical records. Follow-up occurred every 6 months. ICD shock data and clinical outcomes were adjudicated by 2 electrophysiologists. Median age was 33 years (89 subjects <20 years of age); 33% were female. Sixty were competitive athletes (varsity/junior varsity/traveling team). A pre-ICD history of ventricular arrhythmia was present in 42%. Running, basketball, and soccer were the most common sports. Over a median 31-month (interquartile range, 21–46 months) follow-up, there were no occurrences of either primary end point—death or resuscitated arrest or arrhythmia- or shock-related injury—during sports. There were 49 shocks in 37 participants (10% of study population) during competition/practice, 39 shocks in 29 participants (8%) during other physical activity, and 33 shocks in 24 participants (6%) at rest. In 8 ventricular arrhythmia episodes (device defined), multiple shocks were received: 1 at rest, 4 during competition/practice, and 3 during other physical activity. Ultimately, the ICD terminated all episodes. Freedom from lead malfunction was 97% at 5 years (from implantation) and 90% at 10 years.

Conclusions—

Many athletes with ICDs can engage in vigorous and competitive sports without physical injury or failure to terminate the arrhythmia despite the occurrence of both inappropriate and appropriate shocks. These data provide a basis for more informed physician and patient decision making in terms of sports participation for athletes with ICDs.

Three principles for determining the relevancy of store-and-forward and live interactive telemedicine: reinterpreting two telemedicine research reviews and other research

The Agency for Healthcare Research and Quality sponsored two telemedicine research reviews. The latest review concluded that telemedicine is most relevant to specialties, such as psychiatry and neurology, where high levels of patient interaction are crucial to assessment. Telemedicine research studies cited in the reviews having positive findings in the specialties of ophthalmology, otolaryngology, obstetrics and gynecology, gastroenterology, and cardiology and more recent research in these areas are reviewed to identify criteria other than degree of interaction for determining the appropriateness of telemedicine interventions. These criteria include congruity or the extent that procedures used in telemedicine are similar to those of in-person examination, fidelity or the degree to which the information used for assessment in remote examinations is of similar quality to that used in-person, and reliability or the consistency with which information can be gathered and transmitted.

Ranolazine inhibits shear sensitivity of endogenous Na+ current and spontaneous action potentials in HL-1 cells

Na(V)1.5 is a mechanosensitive voltage-gated Na(+) channel encoded by the gene SCN5A, expressed in cardiac myocytes and required for phase 0 of the cardiac action potential (AP). In the cardiomyocyte, ranolazine inhibits depolarizing Na(+) current and delayed rectifier (I(Kr)) currents. Recently, ranolazine was also shown to be an inhibitor of Na(V)1.5 mechanosensitivity. Stretch also accelerates the firing frequency of the SA node, and fluid shear stress increases the beating rate of cultured cardiomyocytes in vitro. However, no cultured cell platform exists currently for examination of spontaneous electrical activity in response to mechanical stimulation. In the present study, flow of solution over atrial myocyte-derived HL-1 cultured cells was used to study shear stress mechanosensitivity of Na(+) current and spontaneous, endogenous rhythmic action potentials. In voltage-clamped HL-1 cells, bath flow increased peak Na(+) current by 14 ± 5%. In current-clamped cells, bath flow increased the frequency and decay rate of AP by 27 ± 12% and 18 ± 4%, respectively. Ranolazine blocked both responses to shear stress. This study suggests that cultured HL-1 cells are a viable in vitro model for detailed study of the effects of mechanical stimulation on spontaneous cardiac action potentials. Inhibition of the frequency and decay rate of action potentials in HL-1 cells are potential mechanisms behind the antiarrhythmic effect of ranolazine.

Video medical interpretation over 3G cellular networks: a feasibility study

OBJECTIVE

To test the feasibility of using cell phone technology to provide video medical interpretation services at a distance.

MATERIALS AND METHODS

Alternative cell phone services were researched and videoconferencing technologies were tried out to identify video products and telecommunication services needed to meet video medical interpretation requirements. The video and telecommunication technologies were tried out in a pharmacy setting and compared with use of the telephone.

RESULTS

Outcomes were similar to findings in previous research involving video medical interpretation with higher bandwidth and video quality. Patients appreciated the interpretation service no matter how it is provided, while health providers and interpreters preferred video.

CONCLUSION

It is possible to provide video medical interpretation services via cellular communication using lower bandwidth videoconferencing technology that provides sufficient quality, at least in pharmacy settings. However, a number of issues need to be addressed to ensure quality of service.

Advanced networks and computing in healthcare

As computing and network capabilities continue to rise, it becomes increasingly important to understand the varied applications for using them to provide healthcare. The objective of this review is to identify key characteristics and attributes of healthcare applications involving the use of advanced computing and communication technologies, drawing upon 45 research and development projects in telemedicine and other aspects of healthcare funded by the National Library of Medicine over the past 12 years. Only projects publishing in the professional literature were included in the review. Four projects did not publish beyond their final reports. In addition, the authors drew on their first-hand experience as project officers, reviewers and monitors of the work. Major themes in the corpus of work were identified, characterizing key attributes of advanced computing and network applications in healthcare. Advanced computing and network applications are relevant to a range of healthcare settings and specialties, but they are most appropriate for solving a narrower range of problems in each. Healthcare projects undertaken primarily to explore potential have also demonstrated effectiveness and depend on the quality of network service as much as bandwidth. Many applications are enabling, making it possible to provide service or conduct research that previously was not possible or to achieve outcomes in addition to those for which projects were undertaken. Most notable are advances in imaging and visualization, collaboration and sense of presence, and mobility in communication and information-resource use.

Internet-based videoconferencing coder/decoders and tools for telemedicine

Alternative videoconferencing technologies for providing telemedicine via the Internet are described. Background information about how digital video applications have been instantiated using Internet protocols is presented. Specific methods for encoding and decoding video are discussed and video applications that have been tested at the National Library of Medicine are reviewed. This article suggests that no one technology is best and that the appropriateness of a method depends on specific applications. Some technologies, however, have lower, more flexible bandwidth requirements and are more standardized, making them more practical. Still, emerging, yet-to-be-standardized applications offer new capabilities warranting further investigation.

Communication and proximity effects on outcomes attributable to sense of presence in distance bioinformatics education

BACKGROUND

Online learning is increasingly popular in medical education and sense of presence has been posited as a factor contributing to its success. Communication media influences on sense of presence and learning outcomes were explored in this study. Test performance and ratings of instruction and technology, factors influenced by sense of presence, are compared under four conditions involving different media and degrees of student physical presence: 1) videoconference co-located, 2) webcast co-located, 3) videoconference dispersed, and 4) webcast dispersed.

METHODS

Eighty one first to forth year medical students heard a lecture on telemedicine and were asked to collaboratively search a telemedicine website under conditions where the lecture was delivered by videoconference or one way streaming (webcast) and where students were either co-located or dispersed. In the videoconference conditions, co-located students could use the technology to interact with the instructor and could interact with each other face to face, while the dispersed students could use the technology to interact with both the instructor and each other. In the webcast conditions, all students could use chat to communicate with the instructor or each other, although the co-located students also could interact orally. After hearing the lecture, students collaboratively searched a telemedicine website, took a test on lecture-website content and rated the instruction and the technology they used. Test scores on lecture and website content and ratings of instruction and technology for the four conditions were compared with analysis of variance and chi-square tests.

RESULTS

There were no significant differences in overall measures, although there were on selected ratings of instruction. Students in both webcast conditions indicated they were encouraged more to follow up on their own and felt instruction was more interactive than co-located videoconferencing students. Dispersed videoconferencing students indicated the highest levels of interaction and there was evidence they interacted more.

CONCLUSION

Results do not strongly support proximity as a sense of presence factor affecting performance and attitudes, but do suggest communication medium may affect interactivity.