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Charles Berul receives award

Charles Berul, M.D., named Pioneer in Cardiac Pacing and Electrophysiology by Heart Rhythm Society

Charles Berul receives award

Dr. Berul receives the Pioneer in Cardiac Pacing and Electrophysiology from the Heart Rhythm Society at their 2021 meeting.

The Heart Rhythm Society has awarded its 2021 Pioneer in Cardiac Pacing and Electrophysiology Award to Charles Berul, M.D., chief of Cardiology and co-director of the Children’s National Heart Institute at Children’s National Hospital.

The award recognizes an individual who has been active in cardiac pacing and/or cardiac electrophysiology for many years and has made significant contributions to the field. It is typically given to electrophysiologists who treat adults. Dr. Berul is the second pediatric specialist to receive it. Dr. Berul accepted his award at Heart Rhythm 2021, the society’s annual meeting.

“It is wonderful news that Dr. Berul is receiving this award in recognition of his major contributions to this field and to improve the lives of children with heart rhythm challenges,” says David Wessel, M.D., executive vice president, chief medical officer and physician-in-chief at Children’s National Hospital. “We are proud of all he has achieved so far, and are so thankful that he shares his expertise, leadership, mentorship and friendship with us at Children’s National every day. Congratulations to him on this tremendous honor.”

The Heart Rhythm Society notes that Dr. Berul has mentored dozens of trainees who have gone on to successful careers and particularly advocates for young investigators and clinician-scientists. He is known for his collaborative style and promotion of faculty physicians in academic medicine. His scientific work began with cellular electrophysiology and clinical genetics of inherited arrhythmia disorders.

He is known for his development of innovative electrophysiologic studies for phenotypic evaluations of genetically manipulated pre-clinical models. Over the past two decades, his research focus and passion have been to develop novel minimally invasive approaches to the heart and improving methods for pediatric pacing and defibrillation.

Dr. Berul is an active member of the Heart Rhythm Society. He has served on multiple society committees, task forces, and writing groups, and is currently an associate editor for the society’s journal, Heart Rhythm. He is also actively involved in other key organizations such as Mended Little Hearts and the Pediatric and Congenital Electrophysiology Society (PACES).

He has more than 300 publications and is an invited speaker nationally and internationally in the areas of pediatric cardiac electrophysiology and miniaturized device development.

Nikki Gillum Posnack

Research team develops new and improved method for studying cardiac function

Nikki Gillum Posnack

While researching how plastic affects heart function in sensitive populations, such as children born with congenital heart defects, Children’s National researcher Nikki Posnack, Ph.D., led a team that developed a new and improved, replicable method of performing simultaneous dual optical mapping to examine electrical activity and calcium for the study of cardiac function.

Since arriving at the Sheikh Zayed Institute for Pediatric Surgical Innovation, researcher Nikki Gillum Posnack, Ph.D., a principal investigator with the institute and assistant professor of pediatrics at the George Washington University School of Medicine and Health Sciences, has been focused on examining how exposure to plastic affects heart function in sensitive populations, such as children born with congenital heart defects. She performs optical mapping to conduct this research, but the industry standard approaches of either using dual cameras or sequential single cameras were cost prohibitive and technically challenging while also diminishing the quality of the imaging results.

Fast forward to July 2019 when Dr. Posnack and her team published “Plasticizer Interaction With the Heart” in the journal Arrhythmia and Electrophysiology, which used imaging techniques to reveal the impact of plastic chemicals on the electrical activity of the heart. Dr. Posnack’s laboratory has since expanded this technique and revealed a new replicable method of performing simultaneous dual optical mapping to examine electrical activity and calcium handling in the heart.

Sharing a new method for studying cardiac function

This groundbreaking method is itself the focus of a new BMC Biomedical Engineering journal article titled “Lights, camera, path splitter: a new approach for truly simultaneous dual optical mapping of the heart with a single camera.”

The article compares and contrasts the current standard for dual camera simultaneous configurations and single camera sequential configurations to Dr. Posnack’s new single camera simultaneous configuration.

Simultaneous dual mapping systems use two probes and dual dyes – one for electrical voltage and the other for calcium. While dual-dye combinations like Di-4-ANEPPS with Indo-1, Di-2-ANEPEQ and calcium green have been developed to separate fluorescence signals by emission, these dye combinations can have spectral overlap, creating the need for non-ideal emission bandpass to negate spectral overlap and/or the inclusion of a calcium probe with an inferior dissociation constant. Additionally, dual-sensor systems require proper alignment to ensure that fluorescence signals are being analyzed from the same tissue region on each individual detector, which could lead to erroneous results. The dual-camera optical setup is expensive, technically challenging and requires a large physical footprint that is often not feasible for basic science and teaching laboratories conducting critical research.

As an alternative, some researchers use a single camera configuration to sequentially image the voltage and calcium probes using excitation light patterning. This approach also has limitations. These single-sensor designs use dual-dye combinations that require two or more excitation light sources, but share a single emission band. Like the dual camera system, this platform design is also technically challenging since the different excitation light wavelengths require light source triggering, camera synchronization and frame interleaving. Due to timing coordination, decreased frame rates, excitation light ramp up/down times and shutter open/close times, single system setups require shorter exposure times compared to dual sensor setups, diminishing the signal-to-noise quality without offering the same temporal fidelity. There is a cost advantage to the single camera system, however, because the additional camera is often one of the most expensive components.

This new single camera, simultaneous dual optical mapping approach is the first multiparametric mapping system that simultaneously acquires calcium and voltage signals from cardiac preparations, using a commercially available optical path splitter, single camera and single excitation light. Using a large field of view sCMOS sensor that is faster and more sensitive, this configuration separates the two emission bands for voltage and calcium probes and simultaneously directs them to either sides of the single, large camera sensor. This protocol employs a commonly used dual-dye combination (RH237 and Rhod2-AM). In contrast, other protocols may require genetically-encoded indicators or fluorescent probes that are not yet commercially available.

The team validated the utility of the approach by performing high-speed simultaneous dual imaging with sufficient signal-to-noise ratio for calcium and voltage signals and specificity of emission signals with negligible cross-talk. Demonstrating the need for simultaneous electrical and calcium sensors, they found that when ventricular tachycardia is induced, there is spatially discordant calcium alternans present in different regions of the heart even when the electrical alternans remain concordant.

Having eliminated the second camera as well as the need for multiple excitation light sources, light pattering and frame interleaving, this system is more cost effective, simpler, and can be easily setup by various types of researchers, not just those with engineering backgrounds.

With a limited research budget and a background in physiology, Dr. Posnack worked collaboratively with her post-doctoral fellow Rafael Jaimes III, an engineer in the Sheikh Zayed Institute for Pediatric Surgical Innovation, to develop a cost-effective system that would enable her to truly study the effects of plastics on the heart.

Multidisciplinary approach

“We’re fortunate to have a multidisciplinary team in the Sheikh Zayed Institute so that I could work with an engineer to develop the technology and system we needed to propel our research,” said Dr. Posnack. “There are so many researchers who have the science background, but not necessarily the technical aptitude, and they get stymied in their research, so we’re proud that this paper will help other researchers replicate the system to study cardiac function.”

The research paper was funded by a grant from the National Institutes of Health as well as support from the Children’s Research Institute, Children’s National Heart Institute and the Sheikh Zayed Institute for Pediatric Surgical Innovation.

The applications for this optical mapping system are significant and Dr. Posnack has been consulted by other research teams looking to implement it in their labs. Additionally, Dr. Posnack has collaborated with several neuroscience teams at Children’s National Hospital, including one that is investigating the effects of hypoxia on brain and heart development, and another that is interested in using image modalities and data processing to analyze calcium as an indicator of neuron firing.

Dr. Posnack continues to use this new dual optical mapping system to further her research as she anticipates the publication of a new article about age-dependent changes in cardiac electrophysiology and calcium handling.

Plastic leaching illustration

Plasticizer interaction with the heart

Calling an ambulance during an emergency, emailing a journal article before a 5 p.m. deadline and maintaining conditions during the fifth week of a 6-week lab study, without altering the light or temperature, requires electricity and translates into time, money and lives saved. During critical moments, we appreciate the tiny particles and ions in electric currents that power our phones, computers or laboratory equipment. We seldom think about the speed of these connections or potential disruptors when conditions are stable. The same applies to the electric currents, or electrophysiology, of our heart.

Arrhythmias affect millions of Americans but can be controlled with routine screenings and preventive care. In an intensive care setting, helping a patient maintain a steady heart rate, especially if they are at risk for cardiac complications, may support a faster recovery, shorter hospital stay, reduced health care costs and improved health outcomes, such as avoiding complications from heart failure or stroke.

A preclinical study, entitled “Plasticizer Interaction With the Heart,” appears in the July issue of Circulation: Arrhythmia and Electrophysiology and examines the role plastic exposure, akin to exposure in a medical setting, has on heart rhythm disruptions and arrhythmias.

changes in heart rhythm due to plastics

New preclinical research finds acute exposure to MEHP, a common plasticizer used in medical equipment, increases risk for alternans and arrhythmias, disruptions in heart rhythm. The images above show changes in heart rhythm, measured by slowed epicardial conduction velocity, enhanced action potential prolongation and impaired sinus node activity.

The research team, led by researchers at Children’s National Health System, discovered increased risks for irregular heart rhythms after exposing intact, in vitro heart models to 30 minutes of mono-2-ethylhexyl phthalate (MEHP), a metabolite from Di-2-ethylhexyl phthalate (DEHP). DEHP is a chemical commonly used to make plastics pliable in FDA-approved medical devices. This phthalate accounts for 40% of the weight of blood storage bags and up to 80% of the weight of tubes used in an intensive care setting, such as for assisted feeding or breathing, and for catheters used in diagnostics or to conduct minimally invasive cardiac procedures.

The team chose to study the heart’s reaction to 60 µM of MEHP, a level comparable to stored blood levels of MEHP observed in pediatric patients and in neonatal exchange transfusion procedures. They found 30-minute exposure to MEHP slowed atrioventricular conduction and increased the atrioventricular node effective refractory period. MEHP prolonged action potential duration time, enhanced action potential triangulation, increased the ventricular effective refractory period and slowed epicardial conduction velocity, which may be due to the inhibition of Nav 1.5, or sodium current.

“We chose to study the impact of MEHP exposure on cardiac electrophysiology at concentrations that are observed in an intensive care setting, since plastic medical products are known to leach these chemicals into a patient’s bloodstream,” says Nikki Gillum Posnack, Ph.D., a principal investigator with the Sheikh Zayed Institute for Pediatric Surgical Innovation at Children’s National and an assistant professor of pediatrics at the George Washington University School of Medicine and Health Sciences. “In critical conditions, a patient may have a blood transfusion, require extracorporeal membrane oxygenation, undergo cardiopulmonary bypass or require dialysis or intravenous fluid administration. All of these scenarios can lead to plastic chemical exposure. Our research team wants to investigate how these plastic chemicals can impact cardiac health.”

In this review, Dr. Posnack’s team mentions one reason for the observed changes in the preclinical heart models may be due to the structure of phthalates, which resemble hormones and can interfere with a variety of biological processes. Due to their low molecular weight, these chemicals can interact directly with ion channels, nuclear receptors and other cellular targets.

Existing epidemiological research shows associations between exposure to phthalates and adverse health outcomes, including metabolic disturbances, reproductive disorders, inflammatory conditions, neurological disorders and cardiovascular disease. This is the first study to examine the link between cardiac electrophysiology in intact hearts and exposure to MEHP, comparable to levels observed in an ICU.

Dr. Posnack’s team previously found DEHP reduced cellular electrical coupling in cardiomyocyte cell models, which slowed conduction velocity and produced an arrhythmogenic phenotype. A microarray analysis found heart cells treated with DEHP led to mRNA changes in genes responsible for contracting and calcium handling. Another preclinical study showed DEHP altered nervous system regulation of the cardiovascular system. Future studies to expand on this research may include the use of larger preclinical models or human assessments. For the latter, stem cell-derived cardiomyocytes can be used to compare the safety profile of plastic chemicals with potential alternatives.

An accompanying editorial, entitled “Shocking Aspects of Nonconductive Plastics,” authored by cardiology researchers at the University of Wisconsin-Madison, puts this novel research into perspective. Like Dr. Posnack, the team notes that while the clinical impact plasticizers have on heart health still needs to be determined, the work contributes to compelling data among multiple researchers and shows DEHP and MEHP are not inert substances.

“Toxic plasticizers in children’s toys and baby products hit public headlines 20 years ago, but exposure to these compounds is up to 25x higher in patients undergoing complex medical procedures,” write the University of Wisconsin-Madison researchers. “We readily (and unknowingly) administer these compounds, and at times in high quantity, to some of our most vulnerable patients. This work highlights the need for further investigation into short and long-term plasticizer exposure on cardiac electrophysiology.”

The Agency for Toxic Substances and Disease Registry (ATSDR), part of the Centers for Disease Control and Prevention (CDC), released a public health statement about DEHP in 2002, noting more research in humans is needed to issue formal warnings against this phthalate.

ATSDR states there is no conclusive evidence about the adverse health effects of children exposed to DEHP in a medical setting, such as procedures that require the use of flexible tubing to administer intravenous fluids or medication. However, the CDC statement includes limits of DEHP exposure, based on preclinical models, used to guide upper DEHP limits in consumer products, including food packaging, drinking water, and air quality in the workplace.

“It’s important to note that this was a preliminary study performed on an ex vivo model that is largely resilient to arrhythmias”, says Rafael Jaimes III, Ph.D., the first author of the study and a senior scientist at Children’s National. “Due to the nature of the design, it was somewhat alarming that we found such significant effects. I predict that electrophysiological disturbances will be more pronounced in models that more closely resemble humans. These types of models should absolutely be studied.”

“And, importantly, our results may incentivize the development and use of new products that are manufactured without phthalates,” Dr. Posnack adds.

These questions are powering Dr. Posnack and her team through a decade-long, multi-institution research investigation to understand how plastic chemicals and medical device biomaterials can impact cardiac health.

Additional study authors for this paper include Damon McCullough, B.S., Bryan Siegel, M.D., Luther Swift, Ph.D., Daniel McInerney, B.S., and James Hiebert, B.S., with the Sheikh Zayed Institute for Pediatric Surgical Innovation and Children’s National Heart Institute, part of Children’s National Health System in Washington, D.C.; Erick A. Perez-Alday, Ph.D., and Larisa G Tereshchenko, M.D., Ph.D., with the Knight Cardiovascular Institute at Oregon Health and Science University in Portland, Ore.; Javier Saiz, Ph.D., and Beatriz Trenor, Ph.D., with Ci2B-Universitat Politecnica de Valencia in Spain and Jiansong Sheng, Ph.D., from CiPA Lab, LLC, in Rockville, Md.

The study was supported by the National Institutes of Health (R00ES023477 and R01HL139472), Children’s Research Institute and Children’s National Heart Institute. NVIDIA corporation provided graphics processing, with partial support by the Direccion General de Politica Cientifica de la Generalitat Valenciana (PROMETEU2016/088).