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Premature Ventricular Contractions

normal
Lead II
25 mm/s10 mm/mV
Heart rate
72bpm
RR
833ms
QT
358ms
Type

Premature Ventricular Contractions

An ectopic focus in the ventricles fires before the next expected beat. The impulse spreads through the myocardium via cell-to-cell conduction (not the His-Purkinje system), producing a wide, bizarre QRS.

Recognition· 4
  • Early beat (premature)
  • Wide QRS complex (>120 ms)
  • No P wave before the QRS
  • Usually followed by compensatory pause
Mechanism

Ectopic ventricular focus fires early — spreads abnormally through muscle

An irritable spot in the ventricles fires prematurely. The impulse spreads slowly through ventricular muscle via cell-to-cell conduction rather than the fast His-Purkinje system. This creates a wide, bizarre QRS. The SA node keeps firing on schedule, so the next normal beat comes at the expected time (compensatory pause).

Findings· 3
  • Early, wide QRS complex (>120 ms) without a preceding P wave.
  • T wave typically deflects opposite to the main QRS vector.
  • Usually followed by a compensatory pause.
Clinical Impact
PVC-induced cardiomyopathy if >10-15% of all beats
↓
Can trigger V-tach in susceptible patients
↓
R-on-T phenomenon can cause V-fib (rare)RISK

Isolated PVCs common and usually benign

Management· 3
1

Primary Treatment

Usually no treatment for occasional PVCs.

2

Frequent or symptomatic

beta-blockers, treat underlying cause (electrolytes, ischemia).

3

Long-term Management

Catheter ablation for refractory cases causing cardiomyopathy.

Differential· 2
PAC with Aberrancy

Premature beat with wide QRS from rate-dependent BBB. Look for preceding abnormal P wave.

Ventricular Tachycardia

Three or more consecutive PVCs = VT by definition. Same wide QRS morphology.