fetal supraventricular tachycardia
Fetal supraventricular tachycardia (SVT) is considered the most common type of fetal tachyarrhythmia and can account for 60-90% of such cases.
Pathology
It has a typical ventricular rate of 230-280 beats per minute (bpm) and is
often associated with an accessory AV conduction pathway. There is a 1-to-1 atrioventricular conduction. A supraventricular tachycardia is only rarely associated with intra- or extra-cardiac anomalies (in contrast to other tachyarrhythmias).
Associations
- Wolff-Parkinson-White syndrome: may be present in ~10% of cases
Radiographic features
Ultrasound/echocardiography
The diagnosis of supraventricular tachycardia can be established using M-mode echocardiography, which may demonstrate paroxysms of atrial tachycardia in the range of 230 - 280 beats per minute (BPM), often following an extra-systole. M-mode echocardiography uses a sampling line placed across atrial and ventricular walls and times electromechanical events in the fetal cardiac cycle. However, it is often not possible to completely identify its precise electropathophysiologic mechanism by this method.
Treatment and prognosis
The management of the fetus with a normal anatomical survey and supraventricular tachycardia is dependent upon the gestational age at diagnosis, and the presence or absence of hydrops fetalis. Digoxin is often considered the drug of first choice. Compared with other arrhythmias, the overall perinatal mortality rate is considered low at ~5-10% (particularly if there are no complications such as the development of hydrops fetalis).
Complications
- development of hydrops fetalis
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