ABSTRACT
Fetal tachyarrhythmias, defined as fetal heart rates about 180 – 200 beats/minute, are generally subdivided into sinus tachycardia, supraventricular tachyarrhythmia, including supraventricular tachycardia (SVT) and atrial flutter, and ventricular tachyarrhythmia. On the other hand, the most common form of fetal and neonatal SVT, the atrioventricular reentry tachycardia via an accessory pathway, involves the atrium, atrioventricular (AV) node, much of the ventricles, and an accessory pathway as reentry circuit, and therefore is a ‘whole heart ’ tachycardia. 1 According to the three electrophysiological levels of the heart, it seems to be more accurate to divide the tachyarrhythmias into atrial tachycardia (atrial flutter, atrial ectopic tachycardia), conduction system tachycardia (atrioventricular reentry tachycardia via an apparent or ‘concealed ’ accessory pathway, permanent junctional reciprocant tachycardia, and atrioventricular nodal reentry tachycardia), and ventricular tachycardia. 1 In fetuses, SVT is more frequent than atrial flutter (70 – 75 % versus 25 – 30 % ), whereas ventricular tachycardia is very rare. 2 Sustained fetal tachy arrhythmia (SVT with 1:1 atrioventricular conduction, atrial flutter, and ventricular tachycardia) may cause congestive heart failure, leading to elevated right atrial and systemic venous pressure, and may be followed by non-immune hydrops, placental edema, and polyhydramnios. In addition, associated maternal complications may be complaints due to severe polyhydramnios, preterm contractions and labor, premature rupture of the membranes, and the so-called mirror syndrome or Ballantyne syndrome. This results in a maternal hyperdynamic and hypertensive state with symptoms of preeclampsia, which is sometimes observed associated with fetuses with placental edema and hydrops of various etiologies. 3-5 If remission of hydrops can be achieved, preeclamptic symptoms of the mother may disappear in the ongoing pregnancy. 6-8
trimesters of pregnancy. Monitoring of the fetal heart rate by ultrasound, continuous wave Doppler (Doptone), or cardiotocography reveals fetal arrhythmia requiring a detailed echocardiographic examination. Polyhydramnios and fetal hydrops may also lead to the detection of an underlying tachyarrhythmia. If an intensive noninvasive and invasive search for an underlying disease is unsuccessful, paroxysmal supraventricular tachyarrhythmia should always be taken into consideration, particularly if signs of congestive heart failure such as cardiomegaly, atrioventricular valvular regurgitation, and/or increased pulsatility of venous flow velocity waveforms is present. In this situation, repeated sonographic heart rate monitoring, or long-term cardiotocography carried out several times per day, can diagnose or exclude paroxysmal supraventricular tachyarrhythmia as the cause of the hydrops.
