A new preclinical study on DEHP plasticizer, commonly used to make PVC and other plastics pliable, found that it has “alarming . . . significant effects” on cardiac electrophysiology.
Researchers led by a team at Children's National Health System (Washington, DC) discovered an increased risk 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-ethylexyl phthalate (DEHP). 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, according to a paper in the July issue of Circulation: Arrhythmia and Electrophysiology. They found that a 30-minute exposure to MEHP slowed atrioventricular conduction and increased the atrioventricular node effective refractory period (the period of time during a cardiac cycle when a new action potential cannot be initiated). 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, said the paper.
"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," said Nikki Gillum Posnack, PhD, 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.
One reason for the observed changes in the preclinical heart models, according to Posnack’s team, 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.
Although several studies have been conducted over the years on the impact of DEHP on human health, the Agency for Toxic Substances and Disease Registry (ATSDR), part of the Centers for Disease Control and Prevention, stated in 2002 that there was no conclusive evidence about the adverse health effects of children exposed to DEHP in a medical setting.
The new study focusing on cardiac arrhythmias is a “preliminary study performed on an ex vivo model that is largely resilient to arrhythmias," said Rafael Jaimes III, PhD, 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," added Posnack.
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