Fetal arrhythmias

Fetal arrhythmias

In fetal complete heart block, anti-Ro SSA antibody may be seen in all cases and anti-la SSB in 70%.
Maternal autoimmune disease is ‘the’ reason for fetal arrhythmia screening. Fetuses with structural heart disease as well as a positive family history calls for fetal arrhythmia screening.

M-mode echo can be used to assess AV relation and so can Doppler. VA interval can be picked up from the Doppler (E – A relation). Those with congenital heart disease have heart block earlier than those with maternal autoimmune disease. Overall prognosis is very poor with an associated structural heart disease.

Some studies suggest steroids for all cases of complete heart block due to maternal autoimmune disease. Dexamethasone is used because it crosses placental barrier while prednisolone may not. Steroid toxicity to the mother may not be a concern because steroids may be indicated for the mother for her autoimmune disease.  Oligohydramnios can occur with steroid treatment.

Fetal tachyarrhythmias

75% of them have SVT while 25% have atrial flutter. Digoxin is a good drug, but not useful in hydrops. Amiodarone is a good drug and so is sotalol. Sotalol can be proarrhythmic. Baseline renal and thyroid function of the mother has to be checked. Higher doses may be required and frequent monitoring is necessary. Delivery should be as close to term as possible as it is easier to take care of a bigger infant. After delivery, the first line is usually digoxin and second line could be beta blockers or amiodarone. Direct current cardioversion may also be resorted to.