Diagnosis and management of common fetal arrhythmias

Abstract

Fetal arrhythmias are detected in at least 2% of unselected pregnancies during routine obstetrical scans. Most common are transient, brief episodes of a slow or fast heart rate or of an irregular heart rhythm. Less common are prolonged or persistent abnormalities such as supraventricular tachycardia and complete heart block which may lead to low cardiac output, fetal hydrops and demise. The objectives of this review are to update the reader on the diagnosis and management of the more common arrhythmias.

Keywords: Congenital atrioventricular block; Fetal arrhythmia; Fetal bradycardia; Fetal echocardiography; Fetal tachycardia.

Figure 1a

M-mode tracing using a four-chamber view to demonstrate atrial (A) and ventricular (V) wall motions. The M-mode beam is directed through the left atrium (LA) and right ventricle (RV).

Figure 1b

Example of a normal Doppler tracing obtained by simultaneous pulse wave Doppler of the aorta and the SVC. The Doppler sample volume is simultaneously placed within the aorta and the SVC.

Figure 2

Conducted PAC. M-Mode tracing from a four chamber view with the transducer beam through the RA and the RV. There is a conducted PAC followed by an early ventricular contraction (V).

Figure 3

Blocked PAC. M-Mode tracing from a four chamber view with the transducer beam through the RA and the RV. There are blocked PAC’s in a trigeminy pattern. Only the normal atrial contractions (A) are followed by a ventricular contraction (V).

Figure 4a

Complete heart block. M-Mode tracing from a four chamber view with the transducer beam through the RA and the LV. There are regular atrial contractions (A) with a normal heart rate of 125 bpm and independent ventricular contractions (V) with a heart rate of 50 bpm.

Figure 4b

Simultaneous pulse wave Doppler of the aorta and vena cava superior of a fetus with complete heart block showing backflow following atrial contractions (A) in the superior vena cava with an atrial rate of 140/min (A) and in the same direction aortic outflow following ventricular contractions (V) which are independent with a regular rate of 60/min.

Figure 5

Atrial flutter. Simultaneous M-Mode tracing to record the RV and LA freewall movements during the cardiac cycles. The atrial rate is very fast and regular at 462 bpm while the ventricular rate is 231 bpm suggesting 2:1 AV conduction.

Figure 6

SVT with a heart rate of 240 bpm. M-Mode tracing through the right atrium (bottom) and the right ventricle (top). There is 1:1 AV-conduction with a short AV-interval.