Fetal tachycardia

Fetal tachycardia is an abnormal increase in the fetal heart rate. It is variably defined as a heart rate above 160-180 beats per minute (bpm) and typically ranges between 170-220 bpm (higher rates can occur with tachyarrhythmias).

The estimated prevalence is ~0.4-1% of pregnancies 3,7.

In the majority of cases, the abnormal electrical impulses originate from the atria.

Classification

A fetal tachycardia can range from a simple sinus tachycardia to various fetal tachyarrhythmias. In a sinus tachycardia there is a 1:1 conduction from the atria through to the ventricles.

Associations

A fetal tachycardia can be associated with many maternal as well as fetal conditions, which include:

Ultrasound
Fetal echocardiography

An M-mode Doppler study is best for assessment of heart rate. It is recommended that the sampling line intercepts both the atrial and ventricular walls, thereby allowing simultaneous assessment of both ventricular and atrial contractility.

Ancilliary features

Ultrasound may also show evidence of associated complications, such as signs of hydrops fetalis.

The long-term prognosis for most fetuses diagnosed with a sinus tachycardia is generally good, with the abnormal rhythm resolving spontaneously during the first year of life in the majority of cases 5. Treatment options (if required) include transplacental administration of antiarrhythmic drugs.

It was first recognised by A S Hyman in 1930 2.

Considerations include:

Ultrasound - obstetric
Share article

Article Information

rID: 13221
Synonyms or Alternate Spellings:
  • Fetal sinus tachycardia
  • Fetal tachycardias

Support Radiopaedia and see fewer ads

Cases and Figures

  • Drag
    Case 1
    Drag here to reorder.
  • Updating… Please wait.
    Loadinganimation

    Alert accept

    Error Unable to process the form. Check for errors and try again.

    Alert accept Thank you for updating your details.