PVC’s (Premature Ventricular Contractions)
Description:
A PVC is an extra abnormal heartbeat that generates from the ventricles. These beats interrupt the regularity of the underlying rhythm, occasionally but not normally, causing an irregular rhythm. The heart’s normal cadence is not interrupted. The different sequence of ventricular depolarization caused a bizarre, wide QRS complex. It has also been known to cause the T-wave to occur in the direction opposite of the QRS complex.
Occasionally, an interpolated beat (a PVC that fails between two sinus beats without interrupting a rhythm) occurs. PVC’s can be classified as unifocal or multifocal depending on if more than one PVC occurs. Unifocal PVC’s are PVC’s with the same morphology, which means they have one pacemaker site. Multifocal PVC’s imply different morphologies which imply two different pacemaker sites. If the distance between the preceding beat and the PVC (also known as the couplet interval) is constant, the PVC’s are likely unifocal.
PVC’s often occur in a pattern of group beatings, such as bigeminy, trigemini and quadrigemini. Bigeminy is a PVC that occurs with every other beat. Trigemini is when every third beat is a PVC. Quadrigemini is when every fourth beat is a PVC. When there are two consecutive PVC’s without a normal complex in between this is known as repetitive PVC’s. Repetitive PVC’s occur in groups of two or three, which is known as couplets and triplets. If there are three or more PVC’s in a row it is considered ventricular tachycardia.
Etiologies:
Myocardial ischemia, increased sympathetic tons, hypoxia, idiopathic causes, acid-based disturbances, electrolyte imbalance, normal variant.
Signs and Symptoms:
Flip-flops, fluttering, pounding or jumping, skipped or missed beats, increased awareness of heartbeat.
Treatment:
Most people with PVC’s and an otherwise normal heart won’t need treatment. Even if bothersome symptoms are present treatment may not be needed because PVC’s are not harmful. If PVC’s develop with patients that have an underlying heart disease their doctors may choose to treat it with basic lifestyle changes such as avoiding caffeine and smoking. Their doctor may also prescribe a beta-blocker as a form of treatment.
Sources:
Brady Paramedic Care, Principles and Practice; Medical Emergencies, Vol. 13 pg 129
MayoClinic.com “Premature Ventricular Contractions (PVC’s)”
AnaesthesiaUK