Atrial dysfunction, widely considered a marker or consequence of other heart diseases, is a relevant clinical entity, which is why it is justified to define atrial failure or insufficiency as “a new syndrome that all cardiologists should be aware of,” said Adrián Baranchuk, MD, PhD, professor of medicine at Queen’s University, Kingston, Ont., during the 2022 48th Argentine Congress of Cardiology in Buenos Aires.
“The atria are like the heart’s silly sisters and can fail just like the ventricle fails. Understanding their function and dysfunction helps us to understand heart failure. And as electrophysiologists and clinical cardiologists, we have to embrace this concept and understand it in depth,” Dr. Baranchuk, president-elect of the Inter-American Society of Cardiology, said in an interview.
The specialist first proposed atrial failure as an entity or syndrome in early 2020 in an article in the Journal of the American College of Cardiology. His four collaborators included the experienced Eugene Braunwald, MD, from Brigham and Women’s Hospital, Boston, and Antoni Bayés de Luna, PhD, from the department of medicine of the autonomous University of Barcelona.
Pathology despite function
“In many patients with heart failure, the pump function is preserved, but what causes the pathology? For the last 5-10 years, attention has been focused on the ventricle: whether it contracts poorly or whether it contracts properly and relaxes poorly. However, we have also seen patients in whom the ventricle contracts properly and relaxes properly. Where else can we look? We started looking at atrial contraction, especially the left atrium,” recalled Dr. Baranchuk.
He and his colleagues proposed the following consensus definition of atrial failure or insufficiency: any atrial dysfunction (anatomical, mechanical, electrical, and rheological, including blood homeostasis) that causes impaired function, heart symptoms, and a worsening of quality of life (or life expectancy) in the absence of significant valvular or ventricular abnormalities.
In his presentation, recorded and projected by video from Canada, Dr. Baranchuk pointed out that there are two large groups of causes of atrial failure: one that has to do with electrical disorders of atrial and interatrial contraction and another related to the progressive development of fibrosis, which gradually leads to dyssynchrony in interatrial contraction, pump failure, and impaired atrial function as a reservoir and as a conduit.
“In turn, these mechanisms trigger neurohormonal alterations that perpetuate atrial failure, so it is not just a matter of progressive fibrosis, which is very difficult to treat, but also of constant neurohormonal activation that guarantees that these phenomena never resolve,” said Dr. Baranchuk. The manifestations or end point of this cascade of events are the known ones: stroke, ischemia, and heart failure.
New entity necessary?
Defining atrial failure or insufficiency as a clinical entity not only restores the hierarchy of the atria in cardiac function, which was already postulated by William Harvey in 1628, but also enables new lines of research that would eventually allow timely preventive interventions.
One key is early recognition of partial or total interatrial block by analyzing the characteristics of the P wave on the electrocardiogram, which could serve to prevent progression to atrial fibrillation. Left atrial enlargement can also be detected by echocardiography.
“When the contractile impairment is severe and you are in atrial fibrillation, all that remains is to apply patches. The strategy is to correct risk factors beforehand, such as high blood pressure, sleep apnea, or high-dose alcohol consumption, as well as tirelessly searching for atrial fibrillation, with Holter electrocardiograms, continuous monitoring devices, such as Apple Watch, KardiaMobile, or an implantable loop recorder,” Dr. Baranchuk said in an interview.
Two ongoing or planned studies, ARCADIA and AMIABLE, will seek to determine whether anticoagulation in patients with elevated cardiovascular risk scores and any of these atrial disorders that have not yet led to atrial fibrillation could reduce the incidence of stroke.
The strategy has a rational basis. In a subanalysis of raw data from the NAVIGATE ESUS study in patients with embolic stroke of unknown cause, Dr. Baranchuk estimated that the presence of interatrial block was a tenfold higher predictor of the risk of experiencing a second stroke. Another 2018 observational study in which he participated found that in outpatients with heart failure, advanced interatrial block approximately tripled the risk of developing atrial fibrillation and ischemic stroke.
For Dr. Baranchuk, other questions that still need to be answered include whether drugs used for heart failure with preserved ejection fraction can be useful in primary atrial failure or whether specific drugs can be repositioned or developed to suppress or slow the process of fibrosis. “From generating the clinical concept, many lines of research are enabled.”
“The concept of atrial failure is very interesting and opens our eyes to treatments,” another speaker at the session, Alejo Tronconi, MD, a cardiologist and electrophysiologist at the Cardiovascular Institute of the South, Cipolletti, Argentina, said in an interview.
“It is necessary to cut circuits that have been extensively studied in heart failure models, and now we are beginning to see their participation in atrial dysfunction,” he said.
Dr. Baranchuk and Dr. Tronconi declared no relevant financial conflict of interest.
A version of this article first appeared on Medscape.com.