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.
A fetal tachycardia can be associated with many maternal as well as fetal conditions, which include:
- maternal hyperthyroidism
- maternal medications
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.
Ultrasound may also show evidence of associated complications, such as signs of hydrops fetalis.
Treatment and prognosis
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.
History and etymology
It was first recognised by A S Hyman in 1930 2.
- 1. Oudijk MA, Visser GH, Meijboom EJ. Fetal tachyarrhythmia--part I: Diagnosis. Indian Pacing Electrophysiol J. 2004;4 (3): 104-13. Indian Pacing Electrophysiol J (link) - Free text at pubmed - Pubmed citation
- 2. Hyman AS. Irregularities of the fetal heart: a phonocardiographic study of the fetal heart sounds from the fifth to eighth months of pregnancy. Am J Obstet Gynecol. 1930;20:332–347.
- 3. Bergmans MG, Jonker GJ, Kock HC. Fetal supraventricular tachycardia. Review of the literature. Obstet Gynecol Surv. 1985;40 (2): 61-8. - Pubmed citation
- 4. Kothari DS, Skinner JR. Neonatal tachycardias: an update. Arch. Dis. Child. Fetal Neonatal Ed. 2006;91 (2): F136-44. doi:10.1136/adc.2004.049049 - Free text at pubmed - Pubmed citation
- 5. Lulić jurjević R, Podnar T, Vesel S. Diagnosis, clinical features, management, and post-natal follow-up of fetal tachycardias. Cardiol Young. 2009;19 (5): 486-93. doi:10.1017/S1047951109990497 - Pubmed citation
- 6. Brown DL. Sonographic assessment of fetal arrhythmias. AJR Am J Roentgenol. 1997;169 (4): 1029-33. AJR Am J Roentgenol (citation) - Pubmed citation
- 7. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
Ultrasound - obstetric
- ultrasound (introduction)
- obstetric ultrasound
first trimester and early pregnancy
- gestational sac
- yolk sac
- Beta-hCG levels
- ectopic pregnancy
- multiple gestations
- subchorionic hematoma
- failed early pregnancy
- fetal biometry
- fetal morphology assessment
- fetal echocardiography views
- nonvisualisation of the fetal stomach
- nuchal fold thickness
- absent nasal bone
- choroid plexus cysts
- enlarged cisterna magna
- shortened fetal long bones
- echogenic intracardiac focus (EIF)
- echogenic fetal bowel
- aberrant right sublavian artery
- fetal pyelectasis / fetal renal pelvic dilatation
- single umbilical artery
- sandal gap toes
- umbilical artery Doppler assessment
- fetal middle cerebral arterial Doppler assessment
- nuchal translucency
- chorionic villus sampling (CVS) and amniocentesis
- first trimester and early pregnancy