We intend to review our experience with the investigation and management of foetal
arrhythmia on the basis of superior vena cava/ascending aorta (SVC/AA) Doppler flow velocity recordings. Irregular rhythms n = 307. Premature atrial and ventricular contractions were easily identified and generally self-limited in time. Sustained
bradycardia n = 19. Four had sinus
bradycardia, six presented with blocked atrial bigeminism, three showed 2:1, and five had a complete atrio-ventricular (
AV) block. Another foetus that presented with first-degree
AV block developed a Luciani-Wenckebach phenomenon 1 week later. These different types of
bradycardia were all identified on SVC/AA Doppler recordings.
Tachyarrhythmia n = 30. Five types of
tachyarrhythmia were observed: Type I: Short ventriculo-atrial (VA)
tachycardia (VA < AV), n = 11. Ten foetuses of this group presented a distinctive Doppler flow velocity pattern characterised by 1:1 AV conduction and a tall atrial wave ('a' wave) superimposed on the aortic ejection wave. They were considered to have re-entrant
tachycardia through a fast-conducting AV accessory pathway; all 10 responded to
digoxin therapy. The eleventh foetus with short VA
tachycardia had
atrial ectopic tachycardia with AV node dysfunction; he was treated successfully with
sotalol. Type II: Long VA
tachycardia (VA > AV): n = 8. In seven cases, an 'a' wave of normal amplitude with normal AV time interval could be clearly identified in front of the aortic ejection wave: one foetus in this group was considered to be in
sinus tachycardia based on the variability of its heart rate; in another, sudden onset of
tachycardia triggered by
extrasystoles led to the possibility of permanent junctional
reciprocating tachycardia (PJRT). The five other foetuses had
atrial ectopic tachycardia. The last foetus presented with AV and VA intervals of the same duration and a heart rate of 210 beats/min; he did not respond either to
digoxin or to
sotalol, and was found after birth to have PJRT. The
drug of first choice in this group was
sotalol. Type III: Simultaneous onset of atrial and ventricular contractions: n = 3. These foetuses were classified as
junctional ectopic tachycardia. Two responded to
amiodarone. The other foetus converted spontaneously to sinus rhythm. Type IV: Flutter: n = 7. All presented with 2:1 AV relationship except one who had a variable block.
Digoxin was prescribed as a first choice associated with
sotalol in three cases. Conversion to sinus rhythm was documented in all; however, one hydropic foetus with advanced
cardiomyopathy died one day after birth. Type V:
Ventricular tachycardia: n = 1. This 30-week foetus presented alternance of AV dissociation (atrial rate: 130, ventricular rate: 170 beats/min) and atrial capture (ventricular rate of 138 beats/min). The
arrhythmia responded well to
propanol, and no recurrence was recorded after birth. Precise prenatal identification of
arrhythmia type can be achieved with the SVC/AA Doppler approach. Such information allows for a better management and a rational choice of appropriate
anti-arrhythmic drug.