Fetal atrial flutter

Fetal atrial flutter is the second most common fetal tachyarrhythmia and can account for up to 30% of such cases ^1,2. 

Clinical presentation

As with other tachyarrhythmias, it is often detected in the 3^rd trimester.

Pathology

It has a typical atrial rate of 300-600 beats per minute (bpm) and often has a variable ventricular rate due to the frequent presence of an atrioventricular (AV) conduction block (often 2:1 atrioventricular conduction ²):

• mean atrial rate: 440-520 bpm ^2,8
• mean ventricular rate: 200-250 bpm ^2,8

Associations

• coexistence of another form of arrhythmia: present in 5-10% of cases
• structural cardiac anomalies
  • Ebstein anomaly
  • pulmonary stenosis

Complications

• development of hydrops fetalis is a serious concern