As more consumer-facing devices add features to measure the heart’s electrical activity, companies are looking for new ways to turn this data into valuable health information. AliveCor, a startup that ...

QT prolongation occurs when the heart muscle takes longer to contract and relax than usual. It can affect heart rhythms and lead to sudden cardiac arrest. The heart is a muscle that contracts and ...

Heart rate reserve (HRR) is the difference between your resting heart rate and your maximum heart rate. Knowing this number can help you train and work on your fitness goals. Your heart rate reserve ...