Assessment of fetal arrhythmia by simultaneous Doppler recording of flow patterns in the ascending aorta and superior vena cava

Abstract

Experimental and clinical data confirm that timing of cardiac mechanical events is better achieved with simultaneous Doppler recordings of ascending aorta (Ao) and superior vena cava (SVC) flow velocity waveforms than with the M-mode technique. We plan to review our experience of the past 4 years with the Doppler approach. Irregular rhythms: n=207. Premature atrial or ventricular contractions were easily identified by both M-mode and SVC/Ao Doppler tracings. Sustained bradycardia: n=18. Four with sinus bradycardia, 6 with blocked atrial bigeminism, 3 with 2:1, and 5 with complete atrio-ventricular (AV) block. Another fetus who presented with a first-degree AV block developed a Luciani-Wenckebach phenomenon 1 week later. These different types of bradycardia were all identified on SVC/Ao Doppler recordings.Tachyarrhythmia: n=23. Six of the 7 fetuses with short VA tachycardia (VA<AV) presented a distinctive Doppler flow velocity pattern: 1:1 AV conduction and a tall “A” wave superimposed on the aortic ejection wave.They were considered to have re-entrant tachycardia through a fast-conducting AV accessory pathway.The seventh fetus with short VA tachycardia had an atrial ectopic tachycardia with AV node dysfunction. In all cases of long VA tachycardia (VA>AV), an “A” wave of normal amplitude with normal AV time interval could be clearly identified in front of the aortic ejection wave. One fetus in this group was considered to be in sinus tachycardia based on the variability of its heart rate; in another, sudden onset of the tachycardia triggered by extrasystoles led to the possibility of permanent junctional reciprocating tachycardia. The other 5 fetuses had atrial ectopic tachycardia. Simultaneous onset of atrial and ventricular contractions was observed in 3 cases diagnosed as junctional ectopic tachycardia. Finally, atrial flutter was diagnosed in 7 fetuses. All presented with a 2:1 AV relationship except 1 who had a variable block. Such information allows for a rational choice of the appropriate anti-arrhythmic drug.