Fetal ventricular tachycardia

A rare entity, fetal ventricular tachycardia presents with a rapid ventricular rate exceeding, and occurring independently from, the atrial rate.  The ventricular rate is typically over 180 beats per minute . Atrioventricular dissociation is characteristic; two separate pacemakers dictate the activity of the atria and ventricles, respectively.

Epidemiology

Occurs in less than 2% of fetal tachydysrhythmia cases. Associated with:

• fetal myocarditis
• long QT syndrome
• complete AV block

Radiographic features

Antenatal ultrasound - echocardiography

Features on M-mode and pulsed wave Doppler (PWD) analysis of cardiac contraction patterns which support the diagnosis of ventricular tachycardia include :

• rapid, regular ventricular activity
  • timing of ventricular depolarization may be accurately timed by the inward excursions of the ventricular walls (M-mode), or systolic V waves (PWD)
• ventricular activity rate exceeds that of the atria
  • independent, dissociated activity of atria and ventricles
  • in rare instances, retrograde conduction from the ventricular pacemaker and (1:1) atrial capture may occur
  • the atrial rate will then closely approximate ventricular rate
    • utilization of tissue Doppler imaging may help elucidate the first structure which contracts