Former Empress Michiko has been diagnosed with heart valve abnormalities, the Imperial Household Agency said Monday.

The 84-year-old former empress, who retired from official duties along with her husband former Emperor Akihito, who abdicated at the end of April, will have follow-up observations, with doctors calling for reducing the burden on her heart in daily life.

Abnormalities were found in the atrioventricular valves that normally function to prevent backflow of blood in a heart, the agency said.

The valves have been found not to close sufficiently but her symptoms are relatively mild, it said. She has also been diagnosed with having an irregular heartbeat.

The former empress underwent a heart exam Saturday after a blood test showed earlier this month a higher risk of heart failure.

She has experienced shortness of breath more frequently than before during her morning walks since the beginning of this year, according to the agency.

In 2015, she suffered from chest pains and had a computed tomography scan of her coronary arteries before being diagnosed with myocardial ischemia, a condition in which there is insufficient blood flow to some parts of the heart.