The condition you describe, bigeminy (bi-gem-i-ne), reflects a slightly abnormal heart rhythm that is usually of no serious concern in the absence of other cardiovascular disease. This condition describes a state where your heart alternates one "normal" beat with one "premature" beat. As you are probably aware, the heart contains cells capable of initiating electrical activity, which are necessary for enabling coordinated heart contractions. While these cells are contained throughout the heart, the sinus node is typically the place where these electrical impulses begin. The term "normal sinus rhythm" describes the normal beating of the heart, where electrical impulses originate in the sinus node (SA node), travel through the atria and atrioventricular node (AV node), and terminate in the ventricles. Premature beats occur when either the atria or the ventricle initiate their own electrical impulse before receiving the impulse from the sinus node. The term "bigeminy" is typically used to describe when normal sinus beats alternate with premature ventricular beats.
All of us at one time or another experience occasional premature heartbeats. In isolation, these are not usually reason for concern. It is useful, however, to have an understanding of what can precipitate premature heartbeats, including bigeminal heart rhythms. Increasing age, tension, anxiety, overeating, exercise, and stimulants such as caffeine, tobacco, alcohol, and over-the-counter decongestants are all associated with greater frequency of premature heartbeats. Medical conditions may include an overactive thyroid and/or abnormal electrolytes, such as low potassium and magnesium levels. Even prescription medications, like diuretics, can deplete potassium and magnesium levels in the normal course of treatment for high blood pressure and cause increased numbers of premature beats.