Premature
Ventricular Contractions
| Rate |
variable |
| P wave |
usually obscured by the
QRS, PST or T wave of the PVC |
| QRS |
wide > 0.12 seconds;
morphology is bizarre with the ST segment and the T wave
opposite in polarity. May be multifocal and exhibit
different morphologies. |
| Conduction |
the
impulse originates below the branching portion of the
Bundle of His; full compensatory pause is characteristic. |
| Rhythm |
irregular. PVC's may occur in singles,
couplets or triplets; or in bigeminy, trigeminy or quadrigeminy. |
PVCs can occur in healthy hearts. For example, an increase in
circulating catecholamines can cause PVCs. They also occur in diseased hearts
and from drug (such as digitalis) toxicities.
Treatment is required if they are:
- associated with an acute MI,
- occur as couplets, bigeminy or trigeminy,
- are multifocal, or
- are frequent (>6/min).
Interventions include:
- lidocaine,
- pronestyl, or
- quinidine.
Instant
Feedback:
Treatment
is usually required if there are more than six PVCs per minute.