Fetal premature atrial contractions: natural course, risk factors and adverse outcome.

OBJECTIVES

Fetal premature atrial contractions (PAC) are usually benign but may be associated with congenital heart defect (CHD) and tachyarrhythmia, which in turn carry a risk of cardiac failure and fetal death. We aimed to explore the frequency of adverse outcome and to identify risk factors for tachyarrhythmia in pregnancies complicated by fetal PAC.

METHODS

This was a retrospective cohort study of fetuses diagnosed with PAC at two academic centers in Amsterdam, The Netherlands, between 2007 and 2022. Cases with a congenital anomaly and those with a prior diagnosis of CHD or other arrhythmias were excluded. M-mode and Doppler tracings were reanalyzed and the frequency of PAC was recorded. The incidence of the following adverse outcomes was examined: underlying CHD not identified at the 20-week fetal anomaly scan, tachyarrhythmia, other arrhythmia, administration of antiarrhythmic therapy and death. Risk factors for tachyarrhythmia were analyzed using odds ratios (OR).

RESULTS

In 24.1% of 1439 referred cases, PAC resolved before confirmation at the fetal medicine unit (FMU). Of the 939 included cases with confirmed PAC, the total incidence of adverse outcome was 6.8% (64/939). CHD was diagnosed in 14 (1.5% (95% CI, 0.9-2.5%)) cases, of which eight were diagnosed prenatally and six postnatally. Compared with baseline, the incidence of CHD was higher in the presence of fetal PAC (OR, 1.8 (95% CI, 1.0-3.3); P = 0.034). Tachyarrhythmia occurred prenatally and/or postnatally in 32 (3.4%) cases, of which eight (25.0%) showed signs of cardiac failure, and in 23 (71.9%) cases, antiarrhythmic therapy was required. No cases of tachyarrhythmia led to fetal or infant death. Risk factors for tachyarrhythmia were PAC with short runs of supraventricular tachycardia (OR, 98.7), blocked PAC (OR, 30.3), PAC in bigeminy (OR, 21.8), frequent PAC (one per 5-10 beats) (OR, 6.9), signs of cardiac failure (OR, 14.2) and the presence of a foramen ovale aneurysm (OR, 5.0).

CONCLUSIONS

PAC are generally benign and often resolve spontaneously. However, fetuses with an irregular heart rhythm should be referred for advanced ultrasonography, which should focus on classifying the type of PAC and risk of adverse outcome. When risk factors for tachyarrhythmia are identified, weekly fetal heart-rate monitoring is advised until resolution of the PAC. In the absence of risk factors, standard obstetric care may be sufficient, with additional instructions to report reduced fetal movements. Should tachyarrhythmia or cardiac failure develop, referral back to the FMU is indicated. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.