Investigation of foetal arrhythmias by simultaneous recording of ascendingaortic and superior vena caval blood

In a period of 18 consecutive months, all the foetus referred to our Foetal Cardiology Unit for investigation of arrhythmia were systematically assess ed by M mode echocardiography and simultaneous recording of blood flow in t he superior vena cava and the aorta (SVC/Ao). This study was undertaken to compare the performance of these two approaches. The foetus were classified into three groups according to the arrhythmia diagnosed: Group 1: irregula r arrhythmias, Group 2: bradycardias, Group 3: tachycardias. A surface ECG was recorded in all the neonates in whom the arrhythmias persisted. In Group 1, including 50 cases of extrasystoles (49 atrial and 1 ventricula r), M mode echo and the Doppler provided the diagnosis in 42 and 47 cases r espectively. This difference was not statistically significant. Group 2 com prised four cases of bradycardia (2 blocked atrial bigeminy, 2 complete atr ioventricular blocks); the two methods provided the diagnosis in all 4 case s. Group 3 comprised 11 cases including 7 supraventricular tachycardias (SV T), 2 flutter, 1 chaotic atrial rhythm and 1 ectopic junctional rhythm. Com plete analysis of these arrhythmias was possible by M mode in 4 cases and b y Doppler in all cases. This difference was significant. The distribution o f the 7 cases of SVT with respect to the duration of the ventriculoatrial i nterval was possible by M mode in 2 cases and in all cases by Doppler. This was a decisive factor in the choice of antiarrhythmic therapy. The authors conclude that Doppler and M mode are two echocardiographic appr oaches which are equally effective in the investigation of foetal atrial ex trasystoles and probably of sustained foetal bradycardia. However, Doppler recording of SVC/Ao gives a more detailed and precise diagnosis of more com plex foetal arrhythmias.