PACs and PVCs are usually harmless but can sometimes indicate underlying heart disease. Atrial fibrillation (AFib) is common and originates within the atria, causing them to "quiver" or fibrillate.

Medically reviewed by Yasmine S. Ali, MD, MSCI Bigeminy is an irregular heart rhythm where every normal beat is followed by an abnormal one, often due to premature ventricular contractions (PVCs). It ...

Unlike premature atrial contractions, or PACs, usually narrow-complexed because ... Ventricular bigeminy occurs when every other beat is a PVC. No treatment is necessary for PVCs.

Note the premature ventricular contraction (PVC) that triggers the AVNRT in this ECG. If a premature atrial contraction (PAC) or premature ventricular contraction (PVC) occurs at the right time ...