"Heart irregularities" refers to any abnormalities or problems with the way the heart beats or functions. It means that the heart is not working as it should, which can affect its ability to pump blood effectively. Full definition
This lead to the Braidwood Inquiry, which concluded that tasers can cause death in people with heart irregularities. (slaw.ca)
No fetal heart irregularities detected with routine monitoring. (bmj.com)
They looked for heart irregularities — premature ventricular and atrial contractions — in the participants over a year, but found that there were no differences among the subjects, regardless of their caffeine intake. (mindbodygreen.com)