Conduction system disease in fetuses evaluated for irregular cardiac rhythm

Area of Science:

• Cardiology
• Maternal-Fetal Medicine
• Pediatric Electrophysiology

Background:

• Irregular cardiac rhythm in fetuses can include isolated ectopy that resolves spontaneously.
• Doppler measurements of the mechanical PR interval can identify prenatal atrioventricular (AV) conduction disease.
• Prenatal therapy for fetal AV conduction abnormalities may prevent disease progression in utero or postnatally.

Purpose of the Study:

• Determine the prevalence of 1st and 2nd degree atrioventricular (AV) block in fetuses presenting with irregular cardiac rhythm.
• Summarize pregnancy outcomes for fetuses diagnosed with 1st or 2nd degree AV block.
• Investigate the potential role of prenatal therapy in managing fetal AV conduction disease.

Main Methods:

• Retrospective review of fetuses with irregular cardiac rhythm between 1996 and 2004.
• Diagnosis of 1st or 2nd degree AV block using Doppler and M-mode, confirmed by fetal magnetocardiography (fMCG) or postnatal 12-lead ECG.
• Administration of dexamethasone to mothers with abnormal fetal AV conduction associated with anti-Ro/anti-La antibodies.

Main Results:

• Eight out of 306 fetuses (2.6%) with irregular rhythm were diagnosed with intermittent 1st or 2nd degree AV block.
• Causes included idiopathic (2), congenital long QT syndrome (2), and maternal anti-Ro/anti-La antibodies (4).
• No intrauterine progression to complete AV block was observed; all infants were born alive between 34-40 weeks gestation.

Conclusions:

• A small but significant proportion of fetuses with irregular rhythms exhibit 1st or 2nd degree AV block.
• Transplacental therapy, such as dexamethasone, may be effective in limiting intrauterine progression of AV block.
• Early diagnosis and intervention are crucial for managing fetal AV conduction abnormalities.