Quantifying effectiveness of treatment for irregular heartbeat

July 17, 2017, Johns Hopkins University School of Medicine
In a healthy heart, the heart's electrical communication system is efficient and effective. During atrial fibrillation, the heart's electrical cells are misfiring, which can increase the risk of stroke, blood clots, and heart failure. Catheter ablation is the procedure to destroy the misfiring heart cells and improve the heart's electrical communication system. This study sought to create a measure of success for catheter ablation, so that physicians and patients could know immediately following treatment whether it was effective, or whether they'll need to anticipate another procedure in the future. Credit: Rachel Sweeney

In a small proof-of-concept study, researchers at Johns Hopkins report a complex mathematical method to measure electrical communications within the heart can successfully predict the effectiveness of catheter ablation, the standard of care treatment for atrial fibrillation, the most common irregular heartbeat disorder. This has the potential to let physicians and patients know immediately following treatment whether it was effective, or whether they'll need to anticipate another procedure in the future.

Atrial fibrillation is the most common irregular heartbeat disorder in America, affecting three to six million Americans, with a projected increase to twelve million by 2030, according to the American Heart Association's Heart Disease and Stroke Statistics 2017 Update. The dangers of Afib, which is caused by misfiring electrical signals in the heart, include a higher risk of stroke, blood clots, and heart failure, and symptoms that may include heart palpitations, shortness of breath and fatigue.

When drugs aren't effective for treating , cardiologists may use a procedure called catheter ablation to cauterize, or burn, the heart tissue that's the source of the electrical misfire. During catheter ablation, which typically takes four to five hours, cardiologists thread a catheter, or long thin tube, up through a blood vessel from the groin to the heart and use it as a conduit to send radiofrequency energy to cauterize the misfiring cells. The hope is that once the faulty tissue is destroyed, the heart's electrical system will improve, and the periodic will cease or occur less intensely or frequently.

Hiroshi Ashikaga, assistant professor of medicine and biomedical engineering at Johns Hopkins University School of Medicine, says that the success rate for atrial fibrillation patients twelve months after the procedure is 60 to 80 percent for ideal candidates with intermittent irregular heartbeats. But for patients who have chronic and persistent , success rates are much lower.

"This means that 20 to 40 percent of patients have to undergo a second, or even third, long procedure; rates no one is happy about," Ashikaga says. "Our study sought to create an accurate predictor and measure of success and we showed that if the procedure improved electrical communication in the heart immediately following , then it can be a read-out for longer term success." Ashikaga published the results of his study on July 5 in the open access journal PLOS ONE.

Ashikaga and his team used a basket-shaped catheter with 64 electrode sensors to measure the heart's electrical communication just before and right after the procedure, and again at six months in 22 patients with an average age of about 64 years treated at the Johns Hopkins Hospital. Seventy-eight percent of patients in the study were male and all patients had persistent atrial fibrillation.

To quantify the health of the heart's complex electrical communication system, Ashikaga's team measured the strength of the communication between all of the different pairs of points that the 64-node catheter can monitor. The heart's structure of communication can be described as a small-world . A small-world network is a structure that Ashigaka describes as somewhere between a regular network and a random network, with a regular network imagined as a circle of 64 people holding hands and being friends only with their neighbors, and a random network imagined as that circle of people having random friendships throughout the circle, irrespective of where they're standing.

"If you want to send a message to someone on the opposite side of the big circle in a regular network, you have to send the message through 32 people to reach that one other person," Ashikaga says. "It takes a long time to relay the message and it's not really efficient."

The opposite of a regular network is a random network, with many arbitrary connections between points. In between a regular and is a small-world network, a combination of regular and random connections that creates an efficient and robust system, "meaning that if one connection is broken, there's still a pathway for communication," Ashikaga explains.

"If the small-world network index of the heart's electrical communication system improved right after the procedure, our data showed that it's predictive of the six-month success rate of the procedure," Ashikaga says. Improvement in the small-world index, indicative of the health of the 's electrical communication system, immediately following the was associated with a successful outcome in six months. For example, successful ablation improves both the local and global connectivity, and as a result, improves the efficiency and robustness of the communication network. These changes are not observed in patients with Afib recurrence.

Ashikaga cautions that larger-scale clinical trials are needed before the measurement can be recommended for wider use.

Explore further: Catheter ablations reduce risks of stroke in heart patients with stroke history, study finds

More information: Susumu Tao et al, Ablation as targeted perturbation to rewire communication network of persistent atrial fibrillation, PLOS ONE (2017). DOI: 10.1371/journal.pone.0179459

Related Stories

Catheter ablations reduce risks of stroke in heart patients with stroke history, study finds

November 13, 2016
Atrial fibrillation patients with a prior history of stroke who undergo catheter ablation to treat the abnormal heart rhythm lower their long-term risk of a recurrent stroke by 50 percent, according to new research from the ...

Ablation for atrial fibrillation proven safe and effective for patients with congenital heart disease, study finds

May 12, 2017
Congenital heart disease (CHD) includes a range of defects that occur in the heart which patients are born with, such as a hole in the heart's wall, a leaky valve or even an inversion in the heart's orientation. CHD was once ...

Imaging technique for treating heart condition should be more widely used to minimize radiation exposure

June 1, 2017
A technique to treat an irregular heartbeat that limits or eliminates patients' exposure to radiation should be more widely adopted by physicians, NewYork-Presbyterian and Weill Cornell Medicine cardiologists argue in a new ...

Reseachers develop new 3-D technology to treat atrial fibrillation

May 11, 2013
Researchers at the Intermountain Heart Institute at Intermountain Medical Center have developed a new 3-D technology that for the first time allows cardiologists the ability to see the precise source of atrial fibrillation ...

Ablation increases survival for adults with atrial fibrillation

July 30, 2014
Adults who undergo a minimally invasive technique to treat atrial fibrillation are significantly less likely to die from a heart attack or heart failure, according to a long-term study by the University of Michigan Frankel ...

More than half of atrial fibrillation patients become asymptomatic after catheter ablation

January 19, 2017
More than half of patients with atrial fibrillation (AF) become asymptomatic after catheter ablation, reports the largest study of the procedure published today in European Heart Journal.

Recommended for you

Researchers borrow from AIDS playbook to tackle rheumatic heart disease

January 22, 2018
Billions of US taxpayer dollars have been invested in Africa over the past 15 years to improve care for millions suffering from the HIV/AIDS epidemic; yet health systems on the continent continue to struggle. What if the ...

A nanoparticle inhalant for treating heart disease

January 18, 2018
A team of researchers from Italy and Germany has developed a nanoparticle inhalant for treating people suffering from heart disease. In their paper published in the journal Science Translational Medicine, the group describes ...

Starting periods before age of 12 linked to heightened risk of heart disease and stroke

January 15, 2018
Starting periods early—before the age of 12—is linked to a heightened risk of heart disease and stroke in later life, suggests an analysis of data from the UK Biobank study, published online in the journal Heart.

'Decorated' stem cells could offer targeted heart repair

January 10, 2018
Although cardiac stem cell therapy is a promising treatment for heart attack patients, directing the cells to the site of an injury - and getting them to stay there - remains challenging. In a new pilot study using an animal ...

Two simple tests could help to pinpoint cause of stroke

January 10, 2018
Detecting the cause of the deadliest form of stroke could be improved by a simple blood test added alongside a routine brain scan, research suggests.

Exercise is good for the heart, high blood pressure is bad—researchers find out why

January 10, 2018
When the heart is put under stress during exercise, it is considered healthy. Yet stress due to high blood pressure is bad for the heart. Why? And is this always the case? Researchers of the German Centre for Cardiovascular ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.