Simultaneous recordings of pulsed wave Doppler signals in hepatic vein and descending aorta using dual Doppler: a novel method for evaluating fetal arrhythmias

Fetal arrhythmias, which affect 1–2% of pregnancies, are common1. Cardiac-rhythm analysis involves recording atrial and ventricular contractions simultaneously. Fouron and Reed introduced simultaneous pulsed Doppler interrogation of flow in the superior vena cava (SVC) and the ascending aorta (AAo) to assess fetal cardiac rhythms2, 3. The SVC-AAo method is widely used to analyze fetal arrhythmias. A-wave reversal in the SVC during atrial systole, and forward flow in the AAo, indirectly define the mechanical relationship between atria and ventricles. However, numerous factors can influence success with this method. Doppler interrogation of low-velocity SVC atrial systolic flow depends on an optimal angle of insonation and a low set wall-motion filter, rendering the signal susceptible to contamination. Furthermore, the A-wave in the SVC might be hidden within the arterial systolic flow spectrum in the AAo and thus be difficult to interpret. When atrial systole coincides with ventricular systole in arrhythmias, the A-wave may not be distinguished from the arterial systolic flow spectrum, or vice versa. The Doppler gate can be placed simultaneously over other arteries and veins (e.g. pulmonary and renal arteries and veins)4-6. These techniques are less limited by the fetal position than is the SVC-AAo method. However, as with the SVC-AAo method, the venous A-wave might be hidden within the arterial systolic flow spectrum when atrial systole coincides with ventricular systole. To evaluate fetal arrhythmias, we simultaneously recorded pulsed wave Doppler signals in the hepatic vein and the descending aorta (DAo) using dual Doppler. Dual Doppler has two separate sample gates, thus allowing simultaneous recording of signals from two locations. We obtained dual Doppler recordings using a Preirus or a EUB-7500 (Hitachi Aloka Medical, Ltd., Tokyo, Japan) ultrasound device. Hepatic veins were visualized in color flow mode in a transverse section of the fetal abdomen, spreading out from the inferior vena cava (IVC) between the ductus venosus opening and the right atrium. The DAo was simultaneously visualized anteriorly and to the left of the spine. One sample gate was placed over a hepatic vein branch about 5 mm from the IVC at an insonation angle of nearly 0° and another gate was placed over the DAo. Each pulsed Doppler signal was displayed simultaneously and separately (Figure 1). The retrograde A-wave in the hepatic vein during atrial systole and the aortic ejection wave in the DAo indirectly define the mechanical relationship between atria and ventricles. Transverse color Doppler image of the fetal liver showing hepatic vein (HV) draining into inferior vena cava (IVC) and descending aorta (DAo) anterior to the spine, not adjacent to the HV. One sample gate is placed over one of the branches of the HV about 5 mm from the IVC and another gate is placed over the DAo. The dual Doppler tracing shows flow in both the HV (above) and the DAo (below). The reversed atrial systolic flow in the HV (A) and the ventricular systolic flow in the DAo (V) are indicated. Recently, fetal hepatic venous Doppler was reported to be useful for the evaluation and diagnosis of fetal extrasystoles7. An optimal angle of insonation can nearly always be obtained for hepatic veins owing to the multiplicity and different orientations of these vessels in the liver, allowing a wide range of insonation windows through a transverse section of the fetal abdomen. Additionally, retrograde atrial systolic flow velocity is usually higher in hepatic veins than in the SVC and the IVC, such that the A-wave in hepatic veins is more distinct and easier to recognize during atrial contractions. However, ventricular contractions are not clearly defined by hepatic venous Doppler, greatly limiting its ability to evaluate cardiac arrhythmias except for extrasystole. The DAo is consistently visualized in transverse sections of the upper abdomen containing hepatic veins. However, the DAo is not adjacent to hepatic veins. Simultaneous recording of pulsed wave Doppler signals in the hepatic vein and the DAo is not feasible using one sample gate. Therefore, we used dual Doppler to record pulsed wave Doppler signals simultaneously in the hepatic vein and the DAo, to evaluate the relationship between atrial and ventricular contractions. The advantage of this method is that retrograde atrial systolic flow is usually detected clearly, even when atrial systole coincides with ventricular systole, because dual Doppler displays pulsed signals in hepatic veins and the DAo separately, making them easy to distinguish. Figure 2 illustrates three different fetal arrhythmias. Dual Doppler recordings of the hepatic vein (HV) and the descending aorta (DAo) from three fetuses with arrhythmias. Reversed atrial systolic flow in the HV (A) and ventricular systolic flow in the DAo (V) are clearly detected in all cases. (a) Trigeminy caused by ventricular extrasystole (VES). The ventricular systolic flow in the DAo is trigeminal, but the rhythm of atrial systolic flow in the HV is regular. (b) Pulsed Doppler recording of the superior vena cava (SVC) and the ascending aorta (AAo) from the same fetus as in (a) with trigeminy caused by VES. The ventricular systolic flow spectra in the AAo are almost hidden behind the high-amplitude A-waves (cannon waves) in the SVC when VES occurs coincidentally with atrial systole, which then makes it difficult to distinguish the VES from the cannon A-waves. (c) Trigeminy caused by supraventricular extrasystole (SVES). Both ventricular systolic flow in the DAo and atrial systolic flow in the HV are trigeminal. (d) Complete atrioventricular block. There is lack of atrioventricular synchrony, with an atrial rate of 118 bpm and a ventricular rate of 54 bpm. To our knowledge, dual Doppler recordings of the hepatic vein and the DAo have not previously been used to assess fetal cardiac arrhythmias. This modality is not yet universally available because only a few fetal echocardiography devices are equipped with dual Doppler. We consider simultaneous recordings of pulsed wave Doppler signals in the hepatic vein and the DAo using dual Doppler to be an easy, rapid method of assessing fetal cardiac rhythms, which should allow precise diagnosis of cardiac arrhythmias. T. Kaji*, K. Maeda*, M. Suto*, M. Sato*, M. Irahara*, * Department of Obstetrics and Gynecology, Tokushima University Hospital, Tokushima 770-8503, Japan