Lead on new therapies for cardiovascular disease
Researchers at The Ohio State University Dorothy M. Davis Heart and Lung Research Institute have discovered a new treatment for atrial fibrillation that could potentially end the irregular heartbeat condition for many patients.
Atrial fibrillation, a condition in which the atria fail to contract in a strong, rhythmic way, is the most prevalent cardiac arrhythmia in the United States. It’s a leading cause of stroke, heart failure and other complications.
The Ohio State University Wexner Medical Center cardiovascular researchers studying the mechanisms of atrial fibrillation found that adenosine, a chemical present in human cells and used in clinical practice, may help physicians pinpoint the exact spot of the arrhythmia source, resulting in more effective ablation (destruction of a small amount of heart tissue that’s causing the irregular heart rhythms), possibly ending recurring atrial fibrillation.
This improved method of identifying drivers of atrial fibrillation was applied to a pilot clinical trial of 10 patients.
Scientists at the Ohio State Wexner Medical Center also discovered that atrial fibrillation drivers don’t always have the shape of a closed loop but may instead consist of “hubs” where the electrical activity of atrial fibrillation is multiplied, much like a small tornado. The study results were reported in The Journal of the American Heart Association.
“Thinking of atrial fibrillation drivers as hubs may change the way we interpret mapping results of the heart to identify these drivers,” says Vadim Fedorov, PhD, a professor of physiology and cell biology at the Ohio State College of Medicine and lead author of the study. “Finding these reentrant atrial fibrillation drivers is key for doing targeted ablation and successfully treating AFib.”
At least 2.7 million Americans live with atrial fibrillation, with some suffering from persistent atrial fibrillation that lasts for longer than seven days at a time. When medications don’t work, physicians use ablation.
To perform an ablation, physicians use a CT scan or MRI of the heart to establish anatomy and create an electrical map showing where to do the procedure. But current clinical multi-electrode maps can be difficult for clinicians to interpret because of the structurally complex 3D atria, or top portion of the heart.
“Some of these atrial fibrillation drivers may be missed entirely or falsely identified, resulting in faulty targeting of heart tissue,” Dr. Fedorov says. “Successful treatment of persistent atrial fibrillation depends on accurate identification of these drivers. It’s critical that we have a better understanding of how the mechanisms of atrial fibrillation drivers work in order to enhance clinical driver ablation.”
Ohio State Wexner Medical Center researchers have been able to study living human atria with persistent atrial fibrillation outside the body. They’ve created the most accurate computer models of human atria to date by using a 3D imaging technique created by Dr. Fedorov.
By injecting novel fluorescent dye into the atria and using infrared light, scientists were able to see through the atrial wall and precisely determine where the atrial fibrillation drivers were, which isn’t possible with current clinical mapping tools.
The human hearts were donated for research by patients of Lifeline of Ohio and the Division of Cardiac Surgery at the Ohio State Wexner Medical Center.
Researchers found that using adenosine can stabilize atrial fibrillation drivers, which improves their detection on clinical mapping systems.
“These study results are exciting,” says John Hummel, MD, director of Clinical Electrophysiology Research at the Ohio State Wexner Medical Center, who led the clinical part of the research. “The use of adenosine can improve mapping where atrial fibrillation drivers are not easily identifiable and allow us to more accurately find the exact source of these drivers and ablate. In our study, 80% of patients who had persistent atrial fibrillation were helped by this safe method.”
Now that Dr. Fedorov and his team have identified atrial fibrillation drivers as hubs of activity, the next step is to study what makes regions of the heart more susceptible to becoming a hub, such as scar tissue or fibrosis within the heart muscle. Knowing this could result in new therapies not only to treat atrial fibrillation, but also to help prevent it.