For many people with heart failure, the condition can be devastating. Almost half of all those admitted to a hospital for this health problem die within one year.

In the face of such a dire prognosis, people with heart failure—especially those who are at high risk for hospital admission or death from the condition—could benefit from starting cardiac rehabilitation or trying other therapies sooner. The challenge comes in identifying those high-risk cases.

It’s been shown that when heart failure worsens, it typically disrupts the body’s autonomic nervous system, which regulates such functions as heart rate, digestion and respiration. This is usually identified by changes in heart rate, but this method is not reliable in patients with atrial fibrillation, a heart rhythm disorder that occurs in 20% to 50% of people with heart failure.            

In an effort to find another way of detecting worsening heart failure, researchers at Kitasato University Hospital in Kanagawa, Japan, decided to investigate whether pupil size—a method that has been used to evaluate autonomic function in people with Parkinson’s disease and diabetes. Because the autonomic nervous system also controls how the pupils of the eyes open and close, the researchers theorized that pupil size could be a predictor of heart failure severity.

Study details: To test this approach, researchers measured the pupil size of 870 patients (average age 67) who were hospitalized for heart failure. To prevent any changes that could occur if the patients’ pupils reacted to light or movement, the study participants wore goggles that blocked such effects.

After five minutes, the patients’ pupils were photographed inside the goggles, and the pupils were rated as above or below average size. With this data, the researchers set out to analyze whether pupil size would predict readmission to the hospital and/or death from heart failure.

Research findings: After about two years, 131 of the study participants had died and 328 had to be readmitted to the hospital for heart failure. After comparing the patients’ pupil sizes to their outcomes, the researchers discovered that those with larger pupils had an 18% lower risk of being readmitted to the hospital for heart failure and a 28% lower risk of dying from any cause. These results were adjusted for factors that could affect the progression of heart failure, such as body mass index (BMI) and kidney function.

Takeaway: Based on these findings, which were published in the European Society of Cardiology journal ESC Heart Failure, the investigators concluded that pupil size is a convenient and effective way to predict heart failure risk.

“Pupil area can be obtained rapidly, easily and non-invasively,” explained study author Kohei Nozaki, PT, MSc, of Kitasato University Hospital’s department of rehabilitation. “Our study indicates that it could be used in daily clinical practice to predict prognosis in patients with heart failure, including those who also have atrial fibrillation.”

With this information, doctors could then be sure to urge heart failure patients with small pupils to get more physical activity and possibly undergo cardiac rehabilitation to help improve their heart condition, according to the researchers.

Note: Pupil size measurement for heart failure should not be used in individuals with severe retinopathy or other eye diseases.

Source: The study titled “Prognostic Value of Pupil Area for All-Cause Mortality in Patients with Heart Failure,” by researchers at Kitasato University Hospital, Kanagawa, Japan. The research was published in ESC Heart Failure, a journal of the European Society of Cardiology.

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