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Ventricular bigeminy is an abnormal heart rhythm that can be detected on an electrocardiogram (ECG). Although isolated instances of ventricular bigeminy can be normal, prolonged ventricular bigeminy might be a sign that the heart is in distress. While there is no specific treatment for ventricular bigeminy, it is a sign to doctors that some abnormal process is occurring in the body and causing harm.
The beating of the heart is coordinated by electrical impulses that originate from the heart's interior. A structure called the sinoatrial (SA) node in the right atrium of the heart normally initiates the impulse that stimulates the heart to beat. The impulse starts in the SA node and travels through the atria to the atrioventricular (AV) node, from where it goes on through the ventricles. This electrical stimulation signals the muscles of the heart to contract.
Although the SA node normally sends out the signal for the heart to beat, other parts of the heart can do this in certain circumstances. In theory, this serves as a backup mechanism to make sure the heart is always able to pump blood. If the SA node fails, another part of the heart will take over the signaling. Pathologic conditions within the body can sometimes irritate different locations of the heart, though, and make them send out abnormal electrical signals ordering the heart muscle to contract unnecessarily.
A premature ventricular contraction (PVC) is the result of an abnormal electrical pacing signal — it is the ventricle's response to being irritated in some way. Examples of conditions that stimulate the ventricle to start irregular contractions include low potassium or low oxygen in the blood, mitral valve prolapse, and poor blood flow to the heart. Ventricular bigeminy is a subtype of PVC, specifically PVC with a pattern of a normal beat paired with an abnormal ventricular beat.
An ECG, which is a device that measures the electrical stimuli running through the heart, can display ventricular bigeminy. The ECG will show a normal beat paced by the SA node — which includes what is known as a P wave, a QRS complex, and a T wave — followed by a ventricular beat. The signal that originated in the ventricle can be distinguished from a normal signal by its wide QRS complex and lack of a P wave.
An isolated incidence of ventricular bigeminy is likely harmless. Multiple instances could be a warning sign that the heart is in danger. A patient can be checked for ventricular bigeminy by continuous cardiac monitoring in the hospital or by a 24-hour monitor worn at home.