Silent Afib: risks of undiagnosed Afib for patients and the healthcare system

GE HealthCare

Doctors discussing afib

By Dr. Anthony C. Pearson, MD, FACC

Symptomatic Afib is quite common worldwide and is increasing in prevalence. Estimates put the global prevalence of clinically diagnosed Afib at approximately 46.3 million individuals in 2016, an increase of three-fold over the last 50 years.1

The condition is associated with a marked increase in stroke risk and mortality. A large percentage of Afib patients, however, experience silent Afib, or Afib with no symptoms, and the best method for identifying those patients and reducing the global burden of disease related to Afib remains a subject of intense debate in cardiology.

Prevalence of undiagnosed Afib

A retrospective cohort study to estimate contemporary prevalence of atrial fibrillation in the United States found that 11% of Afib cases were undiagnosed; the assumed two-year prevalence of silent Afib was 23%. This undiagnosed population was noted to be older and to have higher CHA2DS2-VASc scores.2

The prevalence of previously undetected Afib has also been reported in a number of studies using long-term monitors in patients with no known Afib and without symptoms or arrhythmia. In the ASSERT-III trial published in the Journal of Electrocardiology, among patients 80 years of age and older, 1 in 7 experienced Afib ≥6 mins duration.3

Clinical significance

Stroke is generally considered the most important clinical outcome of undetected Afib, and it is the first sign of underlying Afib for some patients.

Because Afib independently increases the risk of ischemic stroke—a risk which is largely reversible with anticoagulant treatment—it is an attractive target for screening, particularly given the proportion of patients with Afib without symptoms. In fact, the overall age-adjusted risk of stroke in patients with Afib has been found to be five times higher than in the general population, with a two-fold increase in mortality.4

There is also a substantial body of evidence to support this notion based on long-term monitoring of patients with cryptogenic stroke, which is now more frequently termed embolic stroke of undetermined source, or ESUS.

Risks presented by subclinical Afib

When Afib is asymptomatic but diagnosed either by a screening process or analysis of an implanted device, it has been termed subclinical Afib (SCAF).5 According to the ASSERT-III data, silent Afib can be detected in approximately 10% of asymptomatic individuals within three months if they undergo long term monitoring with implanted pacemakers or defibrillators, but it is not clear what to do with the information obtained.

Patients with SCAF can develop heart failure with cardiomyopathy typically tied to Afib-related tachycardia. In the CASTLE-AF trial, Afib burden at 6 months was found to be predictive of adverse cardiac events and all-cause mortality in patients with both heart failure and Afib, consistent with findings from prior similar studies.6

The question of screening

In order to prevent disabling stroke, widespread screening for silent Afib has been proposed using ECG, monitoring, or other modalities. However, it is not clear which method is optimal, what duration of clinically silent Afib is significant, and whether this is a cost-effective approach to public health management of Afib.

The European Society of Cardiology Afib guidelines from 2016 recommended opportunistic screening for Afib without symptoms by pulse palpation, or ECG screening for patients older than 65 years or with high stroke risk factors.7

On the other hand, the USPSTF does not believe there is enough evidence showing that the potential benefits outweigh the risk of ECG screening to warrant such an approach.8

Cost burden of undiagnosed Afib

Several studies have attempted to assess the true cost burden of undiagnosed Afib. Studies have found cost-effectiveness in the detection of silent Afib using wearable devices. For example, in an economic evaluation of Afib screening comparing six strategies using wrist-worn wearable devices, screening was associated with a reduction in stroke incidence by 20 to 23 per 100,000 person-years, and the cost-effectiveness of screening was found to be consistent across multiple scenarios, meeting the acceptability threshold of $100,000 per quality-adjusted life-year (QALY).9

The ASSERT-III study examined the cost-effectiveness of using 30-day continuous outpatient ECG monitoring in patients. In one hundred subjects ≥80 years of age without prior history of Afib, the investigators found Afib ≥6 mins in 14% and Afib ≥24 hrs in 3%. The cost-effective analysis found that "one week of monitoring cost $50,000 per quality-adjusted life-year-gained, 30 days and 60 days of monitoring cost $70,000 and $84,000, respectively."

Best practices for undiagnosed Afib

Afib is a common, chronic disease that is associated with multiple comorbidities and decreased quality of life. These patients are at substantial risk for stroke and death, but simple methods for identifying these patients are available, including opportunistic pulse palpation or 12-lead ECGs during annual physician visits.10

Long-term ECG monitoring using ECG-patch-type devices or personal wireless devices can identify even more undiagnosed Afib. Effective medical therapies have been shown to lower the risk of stroke diagnosed Afib patients substantially, but strong mandates to utilize any of these approaches await randomized studies that show the beneficial effects of this early identification strategy on cardiovascular morbidity and mortality.

Dr. Anthony C. Pearson, MD, FACC is a Professor of Medicine at the St. Louis University School of Medicine Division of Cardiology and specializes in general and noninvasive cardiology. This article has been updated by Yasmine S. Ali, MD, MSCI, FACC, FACP, Editor-in-Chief of Speak for the Heart and Assistant Clinical Professor of Medicine at Vanderbilt University School of Medicine.

The opinions, beliefs, and viewpoints expressed in this article are solely those of the author and do not necessarily reflect the opinions, beliefs, and viewpoints of GE Healthcare. The author is a paid consultant for GE Healthcare and was compensated for creation of this article.


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