Comparing Reentrant Drivers Predicted by Image-Based Computational Modeling and Mapped by Electrocardiographic Imaging in Persistent Atrial Fibrillation

Electrocardiographic mapping (ECGI) detects reentrant drivers (RDs) that perpetuate arrhythmia in persistent AF (PsAF). Patient-specific computational models derived from late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) identify all latent sites in the fibrotic substrate that could potentially sustain RDs, not just those manifested during mapped AF. The objective of this study was to compare RDs from simulations and ECGI (RD_sim/RD_ECGI) and analyze implications for ablation. We considered 12 PsAF patients who underwent RD_ECGI ablation. For the same cohort, we simulated AF and identified RD_sim sites in patient-specific models with geometry and fibrosis distribution from pre-ablation LGE-MRI. RD_sim- and RD_ECGI-harboring regions were compared, and the extent of agreement between macroscopic locations of RDs identified by simulations and ECGI was assessed. Effects of ablating RD_ECGI/RD_sim were analyzed. RD_sim were predicted in 28 atrial regions (median [inter-quartile range (IQR)] = 3.0 [1.0; 3.0] per model). ECGI detected 42 RD_ECGI-harboring regions (4.0 [2.0; 5.0] per patient). The number of regions with RD_sim and RD_ECGI per individual was not significantly correlated (R = 0.46, P = ns). The overall rate of regional agreement was fair (modified Cohen's κ₀ statistic = 0.11), as expected, based on the different mechanistic underpinning of RD_sim- and RD_ECGI. nineteen regions were found to harbor both RD_sim and RD_ECGI, suggesting that a subset of clinically observed RDs was fibrosis-mediated. The most frequent source of differences (23/32 regions) between the two modalities was the presence of RD_ECGI perpetuated by mechanisms other than the fibrotic substrate. In 6/12 patients, there was at least one region where a latent RD was observed in simulations but was not manifested during clinical mapping. Ablation of fibrosis-mediated RD_ECGI (i.e., targets in regions that also harbored RD_sim) trended toward a higher rate of positive response compared to ablation of other RD_ECGI targets (57 vs. 41%, P = ns). Our analysis suggests that RDs in human PsAF are at least partially fibrosis-mediated. Substrate-based ablation combining simulations with ECGI could improve outcomes.

High speed ink aggregates are ejected from tattoos during Q-switched Nd:YAG laser treatments

INTRODUCTION

Dark material has been observed embedded within glass slides following Q-switched Nd:YAG laser treatment of tattoos. It appears that these fragments are ejected at high speed from the skin during the treatment.

METHOD

Light microscopic analysis of the slides reveals aggregates of dark fragmented material, presumably tattoo ink, with evidence of fractured/melted glass. Photomicrographs reveal that the sizes of these aggregates are in the range 12 μm to 0.5 mm.

RESULTS

Tattoo ink fragments were clearly observed on the surface and embedded within glass slides. Surface aggregates were observed as a fine dust and were easily washed off while deeper fragments remained in situ. The embedded fragments were not visible to the unaided eye. Some fragments appeared to have melted yielding an "insect-like" appearance. These were found to be located between approximately 0.2 and 1 mm deep in the glass.

CONCLUSION

Given the particle masses and kinetic energies attained by some of these aggregates their velocities, when leaving the skin, may be hundreds to thousands of metres per second. However, the masses of the aggregates are minuscule meaning that laser operators may be subjected to these high-speed aggregates without their knowledge. These high-speed fragments of ink may pose a contamination risk to laser operators. Lasers Surg. Med. 9999:1-7, 2018. © 2018 Wiley Periodicals, Inc.

Insulin resistance is higher in prepubertal girls but switches to become higher in boys at age 16: A Cohort Study (EarlyBird 57)

BACKGROUND

The risk of type 2 diabetes is increasing in teenage girls, and is associated with their greater insulin resistance (IR).

HYPOTHESIS

We hypothesized that the adverse metabolic profile of girls (compared with boys) would persist from childhood through adolescence.

PATIENTS AND METHODS

Community-based longitudinal cohort of 292 children (147 boys) studied annually from 9 to 16 years.

MEASURES

IR (homeostasis-model-assessment-2), high-density lipoprotein-cholesterol (HDL-C), triglycerides, % body-fat (dual-energy x-ray absorptiometry), pubertal stage (age at peak height velocity), physical activity (accelerometry). Multi-level modelling established the age-related trends in IR and lipids and the influence of covariates.

RESULTS

Each year from 9 to 15 years, girls had 21% to 63% higher IR than boys (girls mean IR 0.73-1.33, boys 0.51-0.89, P < .005). At 16 years the gender difference was not significant (girls IR 0.60, boys 0.56, P = .45). Girls had lower HDL-C from 9 to 12 years, higher triglycerides from 9 to 14 years, greater adiposity throughout, and earlier puberty, but boys were more active than girls (all P < .05). After adjustment for %-fat, puberty and activity, the gender difference in IR between girls and boys aged 9 to 15 years became non-significant (IR girls 0.66-1.01, boys 0.65-1.04, P > .07). However, after adjustment at 16 years, girls' IR was 25% lower than boys' (girls 0.44, boys 0.63, P = .001), and they had 22% higher HDL-C (P < .001) and 20% lower triglycerides (P = .003).

CONCLUSIONS

The higher IR of prepubertal and early pubertal girls diminishes during late puberty, and boys begin to exhibit greater metabolic risk. Despite being leaner and more active, boys at 16 years have higher IR than girls, suggesting future higher risk for diabetes, thus we reject our hypothesis.

Termination of re-entrant atrial tachycardia via optogenetic stimulation with optimized spatial targeting: insights from computational models

KEY POINTS

Optogenetics has emerged as a potential alternative to electrotherapy for treating heart rhythm disorders, but its applicability for terminating atrial arrhythmias remains largely unexplored. We used computational models reconstructed from clinical MRI scans of fibrotic patient atria to explore the feasibility of optogenetic termination of atrial tachycardia (AT), comparing two different illumination strategies: distributed vs. targeted. We show that targeted optogenetic stimulation based on automated, non-invasive flow-network analysis of patient-specific re-entry morphology may be a reliable approach for identifying the optimal illumination target in each individual (i.e. the critical AT isthmus). The above-described approach yields very high success rates (up to 100%) and requires dramatically less input power than distributed illumination We conclude that simulations in patient-specific models show that targeted light pulses lasting longer than the AT cycle length can efficiently and reliably terminate AT if the human atria can be successfully light-sensitized via gene delivery of ChR2.

ABSTRACT

Optogenetics has emerged as a potential alternative to electrotherapy for treating arrhythmia, but feasibility studies have been limited to ventricular defibrillation via epicardial light application. Here, we assess the efficacy of optogenetic atrial tachycardia (AT) termination in human hearts using a strategy that targets for illumination specific regions identified in an automated manner. In three patient-specific models reconstructed from late gadolinium-enhanced MRI scans, we simulated channelrhodopsin-2 (ChR2) expression via gene delivery. In all three models, we attempted to terminate re-entrant AT (induced via rapid pacing) via optogenetic stimulation. We compared two strategies: (1) distributed illumination of the endocardium by multi-optrode grids (number of optrodes, N_opt  = 64, 128, 256) and (2) targeted illumination of the critical isthmus, which was identified via analysis of simulated activation patterns using an algorithm based on flow networks. The illuminated area and input power were smaller for the targeted approach (19-57.8 mm² ; 0.6-1.8 W) compared to the sparsest distributed arrays (N_opt  = 64; 124.9 ± 6.3 mm² ; 3.9 ± 0.2 W). AT termination rates for distributed illumination were low, ranging from <5% for short pulses (1/10 ms long) to ∼20% for longer stimuli (100/1000 ms). When we attempted to terminate the same AT episodes with targeted illumination, outcomes were similar for short pulses (1/10 ms long: 0% success) but improved for longer stimuli (100 ms: 54% success; 1000 ms: 90% success). We conclude that simulations in patient-specific models show that light pulses lasting longer than the AT cycle length can efficiently and reliably terminate AT in atria light-sensitized via gene delivery. We show that targeted optogenetic stimulation based on analysis of AT morphology may be a reliable approach for defibrillation and requires less power than distributed illumination.

Untangling Complex Redox Chemistry in Zeolitic Imidazolate Frameworks Using Fourier Transformed Alternating Current Voltammetry

Two zeolitic imidazolate frameworks, ZIF-67 and ZIF-8, were interrogated for their redox properties using Fourier transformed alternating current voltammetry, which revealed that the 2-methylimidazolate ligand is responsible for multiple redox transformations. Further insight was gained by employing discrete tetrahedral complexes, [M(DMIM)₄]²⁺ (DMIM = 1,2-dimethylimidazole, M = Co^II or Zn^II) which have similar structural motifs to ZIFs. In this work we demonstrate a multidirectional approach that enables the complex electrochemical behavior of ZIFs to be unraveled.

Help from home for depression: A randomised controlled trial comparing internet-delivered cognitive behaviour therapy with bibliotherapy for depression

Major Depressive Disorder (MDD) is a leading cause of the Global Burden of Disease. Cognitive Behavioural Therapy (CBT) is an effective treatment for MDD, but access can be impaired due to numerous barriers. Internet-delivered CBT (iCBT) can be utilised to overcome treatment barriers and is an effective treatment for depression, but has never been compared to bibliotherapy. This Randomised Controlled Trial (RCT) included participants meeting diagnostic criteria for MDD (n = 270) being randomised to either: iCBT (n = 61), a CBT self-help book (bCBT) (n = 77), a meditation self-help book (bMED) (n = 64) or wait-list control (WLC) (n = 68). The primary outcome was the Patient Health Questionnaire 9-item scale (PHQ-9) at 12-weeks (post-treatment). All three active interventions were significantly more effective than WLC in reducing depression at post-treatment, but there were no significant differences between the groups. All three interventions led to large within-group reductions in PHQ-9 scores at post-treatment (g = 0.88-1.69), which were maintained at 3-month follow-up, although there was some evidence of relapse in the bMED group (within-group g [post to follow-up] = 0.09-1.04). Self-help based interventions could be beneficial in treating depression, however vigilance needs to be applied when selecting from the range of materials available. Replication of this study with a larger sample is required.

Sensitivity of reentrant driver localization to electrophysiological parameter variability in image-based computational models of persistent atrial fibrillation sustained by a fibrotic substrate

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, causing morbidity and mortality in millions worldwide. The atria of patients with persistent AF (PsAF) are characterized by the presence of extensive and distributed atrial fibrosis, which facilitates the formation of persistent reentrant drivers (RDs, i.e., spiral waves), which promote fibrillatory activity. Targeted catheter ablation of RD-harboring tissues has shown promise as a clinical treatment for PsAF, but the outcomes remain sub-par. Personalized computational modeling has been proposed as a means of non-invasively predicting optimal ablation targets in individual PsAF patients, but it remains unclear how RD localization dynamics are influenced by inter-patient variability in the spatial distribution of atrial fibrosis, action potential duration (APD), and conduction velocity (CV). Here, we conduct simulations in computational models of fibrotic atria derived from the clinical imaging of PsAF patients to characterize the sensitivity of RD locations to these three factors. We show that RDs consistently anchor to boundaries between fibrotic and non-fibrotic tissues, as delineated by late gadolinium-enhanced magnetic resonance imaging, but those changes in APD/CV can enhance or attenuate the likelihood that an RD will anchor to a specific site. These findings show that the level of uncertainty present in patient-specific atrial models reconstructed without any invasive measurements (i.e., incorporating each individual's unique distribution of fibrotic tissue from medical imaging alongside an average representation of AF-remodeled electrophysiology) is sufficiently high that a personalized ablation strategy based on targeting simulation-predicted RD trajectories alone may not produce the desired result.

Dermatopathology education in the era of modern technology

Continuing technological advances are inevitably impacting the study and practice of dermatopathology (DP). We are seeing the transition from glass slide microscopy to virtual microscopy, which is serving both as an accessible educational medium for medical students, residents and fellows in the form of online databases and atlases, as well as a research tool to better inform us regarding the development of visual diagnostic expertise. Expansion in mobile technology is simplifying slide image attainment and providing greater opportunities for phone- and tablet-based microscopy, including teledermatopathology instruction and consultation in resource-poor areas with lack of specialists. Easily accessible mobile and computer-based applications ("apps"), including myDermPath and Clearpath, are providing an interactive medium for DP instruction. The Internet and social networking sites are enabling rapid global communication of DP information and image-sharing, promoting collaborative diagnostic research and scholastic endeavors.

"Threshold-crossing": A Useful Way to Establish the Counterfactual in Clinical Trials?

A central question in the assessment of benefit/harm of new treatments is: how does the average outcome on the new treatment (the factual) compare to the average outcome had patients received no treatment or a different treatment known to be effective (the counterfactual)? Randomized controlled trials (RCTs) are the standard for comparing the factual with the counterfactual. Recent developments necessitate and enable a new way of determining the counterfactual for some new medicines. For select situations, we propose a new framework for evidence generation, which we call "threshold-crossing." This framework leverages the wealth of information that is becoming available from completed RCTs and from real world data sources. Relying on formalized procedures, information gleaned from these data is used to estimate the counterfactual, enabling efficacy assessment of new drugs. We propose future (research) activities to enable "threshold-crossing" for carefully selected products and indications in which RCTs are not feasible.

Rated and Actual Performance of High School Students as a Function of Sex and Attractiveness

High school pictures of 24 males and 17 females were rated for attractiveness, academic achievement, and sociability by 20 college undergraduates. Grade point averages and scores from standardized achievement tests were obtained from the high school students' school records. Analyses of variance indicated significant effects for sex and attractiveness on all ratings. While no correlations were found between ratings and composite scores on objective achievement tests, females received higher grades than males of a comparable achievement level. Findings suggest that teachers' evaluations are affected not only by academic performance but also by the aspects of the student's physical appearance.

Biochemical analysis of pleural and ascitic fluid: effect of sample timing on interpretation of results

Background: Modified Light's criteria are widely used to categorize pleural fluids as either exudates or transudates. Similarly, the serum-ascites albumin gradient (SAAG) is used in the differential diagnosis of ascites, particularly with reference to the prediction of portal hypertension. Fluid and serum samples are required for both of these to be applied. The effect of the time interval between fluid and serum samples on the interpretation of results has not been studied.

Methods: We examined the effect of sample timing on (a) the application of modified Light's criteria, and (b) the categorization of SAAG as wide (≥11 g/L) or narrow (<11 g/L). Specifically, we compared the use of a 'routine' serum sample, i.e. one that was not formally paired by the requesting clinician with the fluid sample, with serum samples collected within 2 h of the fluid sample.

Results: Of 77 pleural fluids included for analysis, 45/47 were categorized as exudates, and 32/30 as transudates, using near-simultaneous/routine serum samples respectively. Discrepant categorization was observed in two cases ( P=0.74). Of 109 ascitic fluids, SAAG was ≥11 g/L in 100/95 cases, and <11 g/L in 9/14, using near-simultaneous/routine serum samples respectively. Discrepant categorization was observed in five cases ( P=0.27).

Conclusions: With reference to categorizing pleural and ascitic fluids as described above under (a) and (b), in most cases the use of routine serum samples does not alter the fluid categorization compared with the use of serum samples collected within 2 h.

Increased urinary dopamine excretion in association with bilateral carotid body tumours - clinical, biochemical and genetic findings

This report describes a rare case of a patient with increased urinary dopamine excretion in association with bilateral carotid body tumours. Excretion of adrenaline, noradrenaline, metadrenaline, normetadrenaline and 4-hydroxy-3-methoxymandelic acid (HMMA) were within the reference ranges, and an 123I-meta-iodobenzylguanidine (MIBG) scan showed uptake in the neck masses, with no other abnormal uptake anywhere else in the body. The patient is being managed conservatively as the tumours are not amenable to resection on account of their size and vascularity. There are only four previous case reports of dopamine-secreting tumours of the carotid body described in the literature, all of whom were women. The tumours were unilateral in three cases and bilateral in the fourth case. Familial cases of carotid body tumours have a higher prevalence of bilateral tumours than non-familial cases. Recent reports in the literature have suggested that a significant number of patients with extra-adrenal catecholamine-secreting paragangliomas have a genetic mutation in one of the identified susceptibility genes for catecholamine-secreting tumours, despite having no other affected family members, and a mutation has been found in the succinate dehydrogenase gene for this patient.

Effect of Improved Physical and Social Environment on Self-Help and Problem Behaviors of Institutionalized Retarded Males

Two studies are reported on the effects of improvement in the physical and social environment upon the problem behaviors (aggressive, hyperactive, and inappropriate behaviors) and self-help behaviors of severely and profoundly retarded institutionalized males. In Study I, self-help and problem behavior ratings were obtained before and after a 10-week baseline period, and after three successive 10-week periods of exposure to an improved ward environment. Results indicated significant and enduring improvements on self-help and problem behavior ratings, although no formal treatment was employed. In Study II, residents were exposed to a behavioral treatment and an improved setting, or an improved setting alone. Residents were assessed at baseline and after 10 and 20 weeks of treatment or control conditions. Results indicated that significant improvement was obtained on self-help ratings for only the residents who received behavioral treatment. However, for all problem behavior ratings except aggressive behaviors, significant reductions were obtained for both groups. The discrepancies in the findings of the two studies for self-help skills are discussed, and directions for future research and methodological issues are considered.

Development of a curriculum in molecular diagnostics, genomics and personalized medicine for dermatology trainees

BACKGROUND

Results of molecular studies are redefining the diagnosis and management of a wide range of skin disorders. Dermatology training programs maintain a relative gap in relevant teaching.

OBJECTIVE

To develop a curriculum in molecular diagnostics, genomics and personalized medicine for dermatology trainees at our institution. The aim is to provide trainees with a specialty-appropriate, working knowledge in clinical molecular dermatology.

METHODS

The Departments of Dermatology and Pathology and Laboratory Medicine collaborated on the design and implementation of educational objectives and teaching modalities for the new curriculum.

RESULTS

A multidisciplinary curriculum was developed. It comprises: (i) assigned reading from the medical literature and reference textbook; (ii) review of teaching sets; (iii) two 1 hour lectures; (iv) trainee presentations; (v) 1-week rotation in a clinical molecular pathology and cytogenetics laboratory; and (vi) assessments and feedback. Residents who participated in the curriculum to date have found the experience to be of value.

CONCLUSIONS

Our curriculum provides a framework for other dermatology residency programs to develop their own specific approach to molecular diagnostics education. Such training will provide a foundation for lifelong learning as molecular testing evolves and becomes integral to the practice of dermatology.