In Vitro Matured Human Pluripotent Stem Cell-Derived Cardiomyocytes Form Grafts With Enhanced Structure and Function in Injured Hearts.

BACKGROUND: Human pluripotent stem cell (hPSC)-derived cardiomyocytes (hPSC-CMs) have tremendous promise for application in cardiac regeneration, but their translational potential is limited by an immature phenotype. We hypothesized that large-scale manufacturing of mature hPSC-CMs could be achieved through culture on polydimethylsiloxane (PDMS)-lined roller bottles and that the transplantation of these cells would mediate better structural and functional outcomes than with conventional immature hPSC-CM populations. METHODS: We comprehensively phenotyped hPSC-CMs after in vitro maturation for 20 and 40 days on either PDMS or standard tissue culture plastic substrates. All hPSC-CMs were generated from a transgenic hPSC line that stably expressed a voltage-sensitive fluorescent reporter to facilitate in vitro and in vivo electrophysiological studies, and cardiomyocyte populations were also analyzed in vitro by immunocytochemistry, ultrastructure and fluorescent calcium imaging, and bulk and single-cell transcriptomics. We next compared outcomes after the transplantation of these populations into a guinea pig model of myocardial infarction using end points including histology, optical mapping of graft- and host-derived action potentials, echocardiography, and telemetric electrocardiographic monitoring. RESULTS: We demonstrated the economic generation of >1×108 mature hPSC-CMs per PDMS-lined roller bottle. Compared with their counterparts generated on tissue culture plastic substrates, PDMS-matured hPSC-CMs exhibited increased cardiac gene expression and more mature structural and functional properties in vitro. More important, intracardiac grafts formed with PDMS-matured myocytes showed greatly enhanced structure and alignment, better host-graft electromechanical integration, less proarrhythmic behavior, and greater beneficial effects on contractile function. CONCLUSIONS: We describe practical methods for the scaled generation of mature hPSC-CMs and provide the first evidence that the transplantation of more mature cardiomyocytes yields better outcomes in vivo.

Types of clinical reasoning in a summative clerkship oral examination.

INTRODUCTION: Dual-process theory characterizes clinical reasoning (CR) as Type 1 (intuitive) and Type 2 (analytical) thinking. This study examined CR on a summative clinical clerkship structured clinical oral examination (SCOE). METHODS AND SUBJECTS: 511 clinical clerks at the University of Toronto underwent SCOEs. Type 1, Type 2, and Global CR performance were compared to other internal medicine clerkship assessments using descriptive statistics and Spearman correlations. RESULTS: Clinical clerks achieved mean marks >75% on the three clinical reasoning stations, on Type 1 and 2 CR tasks, and the overall SCOE. Performance on the SCOE CR stations correlated with each of the other clerkship assessments: written examination, inpatient, and ambulatory clinic assessments. The correlation of performance between Type 1 and Type 2 clinical reasoning tasks was statistically significant but weak (rs = 0.28). This suggests that defined measures of Type 1 and Type 2 reasoning were indeed assessing distinct constructs. CONCLUSION: Clinical clerks used both Type 1 and Type 2 reasoning with success. This study's characterization of Type 1 and Type 2 CR as separate domains, distinct from existing measures on the SCOE as well as the other clerkship assessments, can suggest a further addition to multimodal clerkship assessment.

Outcomes from sudden cardiac arrest in US high schools: a 2-year prospective study from the National Registry for AED Use in Sports.

BACKGROUND: Sudden cardiac arrest (SCA) is the leading cause of death in athletes during exercise. The effectiveness of school-based automated external defibrillator (AED) programmes has not been established through a prospective study. METHODS: A total of 2149 high schools participated in a prospective observational study beginning 1 August 2009, through 31 July 2011. Schools were contacted quarterly and reported all cases of SCA. Of these 95% of schools confirmed their participation for the entire 2-year study period. Cases of SCA were reviewed to confirm the details of the resuscitation. The primary outcome was survival to hospital discharge. RESULTS: School-based AED programmes were present in 87% of participating schools and in all but one of the schools reporting a case of SCA. Fifty nine cases of SCA were confirmed during the study period including 26 (44%) cases in students and 33 (56%) in adults; 39 (66%) cases occurred at an athletic facility during training or competition; 55 (93%) cases were witnessed and 54 (92%) received prompt cardiopulmonary resuscitation. A defibrillator was applied in 50 (85%) cases and a shock delivered onsite in 39 (66%). Overall, 42 of 59 (71%) SCA victims survived to hospital discharge, including 22 of 26 (85%) students and 20 of 33 (61%) adults. Of 18 student-athletes 16 (89%) and 8 of 9 (89%) adults who arrested during physical activity survived to hospital discharge. CONCLUSIONS: High school AED programmes demonstrate a high survival rate for students and adults who suffer SCA on school campus. School-based AED programmes are strongly encouraged.