To the Editor:
Fetal atrial flutter (AF) is a reentrant tachyarrhythmia characterized by very fast, regular atrial and ventricular rates (400-500 bpm and 200-220 bpm, respectively). It occurs mainly in an anatomically normal heart and is usually treated with digoxin, which is often effective, with no further recurrence.1
Maternal autoimmunity leading to transplacental SSA/SSB antibody passage may constitute a rare cause of AF. It is still unclear if extranodal atrial myocardial involvement is an isolated event in neonatal lupus erythematosus (NLE) or if it could precede the atrioventricular (AV) conduction system involvement.
We report the case of a 31-year-old woman presenting for a routine obstetric visit at 29 gestational weeks, during which fetal AF (2:1 transmission) was identified (Figure 1). Fetal structural and functional organ abnormalities were excluded. Maternal clinical examination and electrocardiogram were normal. Screening tests for infectious diseases and thyroid function, as well as drug intake history, were negative. Subsequently, screening tests for autoimmune diseases potentially linked to fetal heart pathology were completed.2
M-mode ultrasound showed (A) ventricular rhythm of 164 bpm, and (B) atrial rhythm of 286 bpm, revealing atrial flutter.
High titers of SSA/SSB antibodies (IgG; 240 U/mL and 320 U/mL, respectively) and antinuclear antibodies (ANA; titer of 1:2560, speckled pattern), as well as ultrasonographic abnormalities of the major salivary glands (SGs) compatible with subclinical Sjögren disease (SjD), were detected (Figure 2A).3
Ultrasound assessment (16 MHz probe) at (A) baseline at the parotid gland level (arrowheads), showing an inhomogeneous echostructure with focal hypoechoic/anechoic areas (arrows); and (B) 2-year follow-up at the parotid gland level, showing a more advanced stage, with larger hypoechoic areas and fibrotic tissue separating them.
Dexamethasone (8 mg intravenously BID for 24 hours and continued with 2 mg orally once daily) and hydroxychloroquine (HCQ) therapy (200 mg orally BID) were initiated and continued up to delivery. For the first 24 hours, 1 mg of digoxin was given intravenously and continued with 0.25 mg orally BID for the next 48 hours.1,4,5 The fetal heart rate and rhythm normalized in the first 48 hours. No corticosteroid (CS) therapy–related fetal side effects were detected.
At 38 gestational weeks, a healthy boy, weighing 2970 g with an Apgar score of 9, was vaginally delivered. At birth, high titers of fetal SSA/SSB antibodies were detected, with full clearance at 4 months. The child developed no symptoms of NLE or adrenal suppression. No arrhythmia episodes were recorded in the perinatal period or afterward.
Two years later, the maternal clinical picture and SG biopsy proved compatible with primary SjD according to current classification criteria.6 The SG ultrasound showed progressive structural damage (Figure 2B).
SjD is an autoimmune disease with a peak onset at 40-49 years of age. Current trends toward advanced maternal age pregnancies have further increased the incidence of prepregnancy or gestational-onset SjD. Immunologically, SjD is characterized by the presence of ANA and SSA/SSB antibodies that can cross the placenta from 12 gestational weeks.6 Because these antibodies have a high specificity for cardiomyocytes, especially SSA/Ro52-kD, they can affect the fetal myocardium and AV conduction system, generating inflammation, arrhythmias, and fibrosis. Once the stage of fibrosis is reached, these myocardial alterations are mostly irreversible.
Early myocardial inflammation may induce sustained fetal supraventricular tachyarrhythmias, but the direct inflammatory involvement of the AV conduction system or onset of fibrosis may lead to different degrees of congenital AV block (CAVB).7
In fact, fetuses who have exposure to maternal autoantibodies may present very diverse cardiac manifestations. The classically associated fetal heart pathology is irreversible CAVB, but the spectrum of fetal cardiac manifestations is much broader and is continuously being expanded.1,8 Ultimately, there is a possibility for rapid transition from non-CAVB cardiac involvement to CAVB.
Indeed, the evolution toward CAVB is extremely unpredictable, with the duration of progression from a normal sinus rhythm sometimes taking less than 24 hours.9 Therefore, one may hypothesize that this sequence of events could appear in fetuses initially diagnosed with tachyarrhythmias.
In our case, immediately after fetal AF detection, CS therapy was initiated in order to temper the fetal myocardial inflammation and to prevent further fibrosis and AV sinus involvement. Only 3 days of digoxin treatment were prescribed, at which point rapid sinus rhythm conversion was obtained. This cautionary measure was taken because of the high baseline SSA/SSB antibody titers exposing the fetus to a higher risk of associated CAVB development.8 The choice for dexamethasone was based on the fact that fluorinated steroids are not inactivated by the placental hydroxylase and are thus regularly used to improve myocardial performance and potentially reverse carditis.1,5,8 Further, the maternal SSA/SSB antibody titers were deemed high, implying additional therapy with HCQ could be safely prescribed throughout pregnancy and during breastfeeding.10
In conclusion, the occurrence of fetal AF may be coincidental with undetected maternal pathology, but it may also represent a red flag for maternal autoimmunity leading to transplacental pathogenetic antibody passage. In contrast to other tachyarrhythmias, AF is observed only in the third trimester, which is probably related to the large atrial size achieved during this gestational time frame.1 AF has a relatively good prognosis if sinus rhythm conversion is attained in utero. Still, the postnatal monitoring of a newborn must continue until full antibody clearance is obtained, owing to the residual risk of developing postnatal-onset complete AV block.8
Footnotes
The authors declare no conflicts of interest relevant to this article.
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