Electrical Changes Predict Heart Failure

A new study has shown that electrical changes in the heart, long before a patient shows any clinical symptoms, can spur a later phase of changes that lead to heart failure caused by arrhythmias.

Scientists isolated small samples of heart tissue about the size of large postage stamps from dogs in various stages of heart failure. Using a technique called optical mapping, they stained the tissue samples with voltage- or calcium-sensitive dyes and excited the photosensitive dyes by shining a green light on them. The dyes emitted light in different amounts, depending on the cellular voltage or calcium levels in the individual tissue samples. The emitted light was collected by a sensitive optical detection system, converted to current, and stored on a computer for analysis.

The researchers demonstrated that electrical disturbances occurred in two distinct phases relative to mechanical abnormalities. The early changes involved a delay in the timing of electrical recovery of heart muscle following each beat, whereas the later changes involved the loss of electrical synchrony among various regions of the heart. The early changes likely contributed to mechanical abnormalities that led to the later changes. Both the early and late changes in electrical properties were necessary to cause a lethal arrhythmia. The researchers estimate that up to 50% of deaths in patients with heart failure are unexpected and sudden, and are the result of lethal arrhythmias.

"By the time most patients are diagnosed with heart failure, it's too late to really improve their condition,” said Fadi G. Akar, Ph.D., a research assistant professor at the Johns Hopkins School of Medicine (Baltimore, MD, USA). "By defining the early electrical changes, we hope to identify new targets for therapy that can either reverse or, at the very least, hinder the progression of the vicious cycle of events that ultimately leads to death.”

Nearly five million people suffer from heart failure in the United States alone every year and more than 250,000 die annually from the condition. The incidence and prevalence of heart failure continue to increase with the aging of the population.




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