From the Guidelines
Fetal tachycardia is a condition that requires immediate evaluation and management to prevent adverse outcomes, and it is defined as a sustained fetal heart rate above 160 beats per minute. When detected, it is crucial to determine the underlying cause, which can include maternal fever, infection, hyperthyroidism, medication effects, fetal anemia, or cardiac arrhythmias 1. The management of fetal tachycardia depends on the underlying cause, and it may involve treating maternal fever with acetaminophen, addressing infections with antibiotics, or managing maternal hyperthyroidism. For primary fetal arrhythmias, maternal administration of antiarrhythmic medications such as digoxin, flecainide, or sotalol may be required 1. Some key points to consider in the management of fetal tachycardia include:
- Continuous fetal monitoring is essential during treatment
- Delivery may be indicated if tachycardia persists and threatens fetal well-being, particularly after 34 weeks gestation
- The concern with prolonged tachycardia is the risk of high-output cardiac failure and development of fetal hydrops, which significantly increases perinatal mortality 1. Therefore, prompt identification and management of the underlying cause is crucial for improving fetal outcomes, and it is essential to follow a systematic approach to interpretation of fetal heart rate tracings, such as the DR C BRAVADO mnemonic, to guide management decisions 1.
From the Research
Definition and Causes of Fetal Tachycardia
- Fetal tachycardia is a rare complication during pregnancy, with supraventricular tachycardia being the most common cause of primary sustained fetal tachyarrhythmia after exclusion of maternal and fetal conditions that can result in secondary fetal tachycardia 2.
- Fetal tachyarrhythmias can be due to various mechanisms, including atrioventricular reentrant type of supraventricular tachycardia and atrial flutter 3.
Diagnosis and Treatment of Fetal Tachycardia
- Fetal echocardiography remains the main tool for diagnosing and discerning the mechanism of tachyarrhythmia 3.
- The goals of therapy for fetal arrhythmias are to restore sinus rhythm, resolve heart failure, and postpone delivery before term 3.
- Digoxin is the most commonly employed first-line antiarrhythmic drug for supraventricular tachycardia, while flecainide, sotalol, and amiodarone are also used in certain cases 2, 3, 4.
- Amiodarone has emerged as a second-line treatment after digoxin failure in nonhydropic fetuses and the most effective treatment for drug-refractory fetal tachycardia accompanied by hydrops 3, 4.
- Intravenous acetaminophen may also be used to treat intrapartum fever and resolution of fetal tachycardia 5.
Management and Outcome of Fetal Tachycardia
- Transplacental therapy can improve prognosis dramatically, and the therapeutic protocol is well defined 4.
- The success rate of transplacental therapy can be as high as 77% to 80% in certain cases 4, 6.
- Maternal and fetal monitoring are crucial during treatment to minimize adverse effects and optimize outcomes 2, 3, 6.
- Fetal arrhythmias can be classified into three main groups: irregular rhythms, tachyarrhythmia, and bradyarrhythmia, and detailed anatomical evaluation and fetal echocardiography are necessary to determine the type of fetal arrhythmia and accompanying structural cardiac and extracardiac anomalies 6.