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Stanford University School of Medicine

Atrial fibrillation more common than previously reported, study finds

Atrial fibrillation, the most common type of heart arrhythmia, affects millions of Americans. People with Afib can experience an irregular heartbeat, heart palpitations, shortness of breath, lightheadedness, fatigue and chest pain.

However, some people with Afib have no symptoms — making it difficult to diagnose the disease early enough to overcome the increased risk of heart failure and stroke. New research suggests this may be a bigger problem than previously thought.

“The incidence and prevalence of Afib have not been well defined as patient symptoms are not a reliable indicator of Afib,” said Javed Nasir, MD, a Stanford cardiac electrophysiology fellow. “Most Afib episodes are asymptomatic and most symptoms thought by patients to be Afib are actually not associated with the arrhythmia. Furthermore, Afib is an intermittent disease and doesn’t lend itself to robust detection with traditional intermittent monitoring modalities, such as ECG or Holter monitors.”

To see just how widespread undetected Afib may be, Nasir led a screening trial using insertable cardiac monitors (ICMs). ICMs are single-lead ECG monitoring devices, about one-third the size of an AAA battery, that are inserted under the skin of the chest. The devices can automatically detect and record Afib episodes and can remotely transmit the data to a doctor’s office.

“Recently there have been significant advances in technology, and we now have very small ICMs with the ability to continuously monitor for Afib for years,” Nasir said. “We started this trial with the hopes of using this technology to identify a population with a high risk of Afib.”

The research team used ICMs to screen almost 250 elderly people with a mean age of 74 years and with no history of atrial fibrillation. They followed the patients for 18 months with monthly remote analysis of the ICM data that was reviewed by cardiologists. As recently reported in Heart Rhythm, they found that 22 percent of the participants were newly diagnosed with atrial fibrillation.

“While classically we could give a 40-year-old adult a 25 percent chance of developing Afib in their lifetime, in our trial we nearly saw this with only 18 months of monitoring,” Nasir said.

The study also demonstrated that the majority of these newly diagnosed Afib patients were then treated with oral anticoagulants, which have been shown to significantly reduce the risk of stroke in patients with Afib detected with pulse palpation or an ECG.

Yet more research is needed, Nasir said:

We have begun to appreciate that stroke risk varies with the amount of Afib, and the Afib found with ICM screening tends to be brief and asymptomatic. Before we recommend routine screening for Afib with ICMs, it is important to wait for the results of on-going trials that are evaluating the risks and benefits of oral anticoagulants in patients with device detected Afib. And we will need to carefully consider the costs of screening with ICMs.

Previously: A new tool to treat atrial fibrillationWomen with heart-rhythm disorder hospitalized for stroke more often than men, Using “big data” to improve patient care: Researchers explore a-fib treatments and Stanford launches Center for Digital Health
Photo by BruceBlaus

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