Premature Ventricular Contractions

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.

Premature ventricular contractions (PVCs) are the result of an ectopic pacemaker located within the ventricle. Because the depolarization wave is initiated outside the His-Purkinje conduction system it travels more slowly throughout the ventricles. The slow conduction results in a wide and abnormally shaped QRS. PVCs can occur randomly or following every normal beat (bigeminy), or following every second normal beat (trigeminy).•

Factors that increase the risk of PVCs include male sex, advanced age, African American race, hypertension and underlying ischemic heart disease, a bundle-branch block on 12-lead ECG, hypomagnesemia, and hypokalemia.

PVCs can occur in healthy hearts and may simply be a response to: increased catecholamines, caffeine, hypoxia, fever, drug toxicity, hypercalemia, hypokalemia or hypomagnesemia. They may also be indicative of, cardiomyopathy, valvular disease, atherosclerosis, endocarditis. PVCs can predispose to serious arrhythmias if they occur in association with an acute MI or during the preceeding T-wave.

PVC treatment•

Asymptomatic patient with no history of cardiac disease; eliminate the underlying cause.

Symptomatic patient (palpitations, angina, syncope)

Treat ischemia

Avoid aggravating factors: stress, sympathomimetics,

Beta-blockade if hemodynamically stable

Lidocaine IV if hemodynamically unstable involving long QT interval

Amiodarone to suppress hemodynamically unstable VT refractory to beta-blockade

Symptomatic with frequent monomorphic PVCs refractory to medical therapy, ablation therapy may be considered