Premature beats in sinus rhythm are often referred to as atrial prophase contractions, also known as atrial premature, because of the presence of early atrial ectopic beats on top of sinus rhythm. This condition can occur in people of all ages, but it is relatively rare in young people and children, and relatively common in older people, often in combination with organic heart disease, such as hypertensive heart disease, coronary heart disease, or pulmonary heart disease, for whom atrial presystole in sinus rhythm is relatively common. In addition, patients with coronary atherosclerotic heart disease or unstable angina pectoris may also experience frequent premature contractions in sinus rhythm.