The ECG Rhythms content is currently under development and is being updated by medical professionals.
Premature ventricular contractions (PVCs) are extra heartbeats that originate in one of the heart’s ventricles, the two lower pumping chambers, instead of the usual impulse from the sinoatrial (SA) node. These irregular beats disrupt the normal heart rhythm and can sometimes be felt as a fluttering or skipped beat.
Analogy: “A sudden, strong drumbeat interrupting the regular rhythm of the song.”
On an ECG, PVCs are characterized by a wide QRS complex, typically greater than or equal to 0.12 seconds (or > 3 small squares), with an abnormal and often bizarre morphology. These beats occur prematurely, meaning they appear earlier than the next expected sinus beat. A PVC is usually not preceded by a P wave, as the electrical impulse originates in the ventricle itself. Following a PVC, there is often a full compensatory pause, where the subsequent normal heartbeat occurs after an interval that is approximately twice the length of the preceding normal R-R interval. The ST segment and T wave of a PVC typically show discordance, meaning they are directed opposite to the main deflection of the QRS complex. PVCs can arise from a single site in the ventricles (unifocal), in which case they will have a consistent appearance on the ECG, or from multiple sites (multifocal), resulting in PVCs with different morphologies.
Many people who experience premature ventricular contractions do not have any noticeable symptoms. However, when symptoms are present, they may include palpitations, a sensation of the heart fluttering, pounding, or jumping in the chest, or a feeling that the heart has skipped a beat. Some individuals may also experience an increased awareness of their heartbeat or a pounding sensation in the neck. Occasional PVCs are generally not a cause for concern, especially in individuals without underlying heart conditions. However, frequent PVCs or certain patterns of PVCs may be associated with an increased risk of developing more serious heart rhythm problems or a weakening of the heart muscle. PVCs can be triggered by factors such as stress, anxiety, caffeine, alcohol, tobacco, certain medications, electrolyte imbalances, or underlying heart conditions.
“Like a sudden hiccup in the heart’s rhythm, the ventricles contract prematurely.”