Main findings and interpretations:
Bradyarrhythmias and ectopies:
Bradyarrhythmias emerged as the predominant fetal arrhythmia (23/40) in
our study, followed by irregular rhythms (9/40) and fetal
tachyarrhythmias (8/40). This finding diverges from previous
studies8-10 where fetal arrhythmias manifested
commonly as irregular rhythms and were mostly deemed benign with minimal
impact on fetal hemodynamics and often resolve spontaneously without
intervention. However, among the cases of irregular rhythms also we
found 5/9 cases associated with SHD, leading to adverse outcomes such as
one IUD, one MTP for complex cardiac anomaly and one infant mortality.
We also saw a case of PAC with a bigeminal pattern which progressed to
SVT. This highlights the need for careful monitoring and proactive
management of fetal cardiac rhythm abnormalities, even when irregular
rhythms are present.
Our study reveals that only 26.1% (6/23) of fetal bradyarrhythmia cases
were associated with structural cardiac anomalies, contrasting the
literature reports11,12 where such associations were
seen in approximately half of the cases. Moreover, both maternal SLE and
anti-Ro/La antibody positivity was observed in 39.1% (9/23) of fetal
bradyarrhythmia cases , emphasizing the need for heightened awareness of
maternal health conditions impacting fetal cardiac rhythm and the
importance of screening and early intervention in at-risk populations.
Management of fetal bradyarrhythmia poses unique challenges, especially
in cases of CHB where an expectant approach is primarily employed, as
there is no documented evidence of reversing an established third-degree
block.5,16 Options like beta-adrenergic agents,
immunoglobulin, and plasmapheresis are not preferred due to unclear
efficacy and potential maternal risks.17-19,21,22 A
study by Jaeggi et al.20suggested a survival rate
above 90% for antibody-related CHB if maternal high-dose dexamethasone
was initiated at the time of anomaly diagnosis and maintained throughout
pregnancy. Another meta-analysis in 2018, including five different
observational studies with second-degree immune-mediated CHB, concluded
that the use of fluorinated glucocorticoids should not be discouraged
unless more robust evidence is available.16 In our
study, all cases with CHB (16/40) and AV block (4/40) received treatment
with dexamethasone until delivery, and HCQ was added for cases with SLE.
There were in total 14/20 live births among these cases, supporting
existing literature that emphasizes the positive role of dexamethasone
in improving outcomes in such cases. Similarly, in cases of isolated
atrioventricular (AV) block, early initiation of treatment and close
monitoring contribute to favorable outcomes, as illustrated by
successful reversion to sinus rhythm in cases managed expectantly.
Tachyarrhythmias
Fetal tachyarrhythmias, occurring in 0.4 to 0.6% of
pregnancies,23 can lead to severe complications if
left untreated, including nonimmune hydrops, premature delivery, fetal
demise, and perinatal morbidities. However, the requirement for
therapeutic intervention in this condition remains a subject of ongoing
debate, centered on the natural progression of the disease. Divergent
opinions range from advocating non-intervention approach to aggressive
pharmacotherapeutic intervention. Transplacental treatment by indirect
drug administration to the mother appears to be the most preferred
approach.23,24
SVT stands out as the most common contributor, accounting for 70-75% of
cases, followed by atrial flutter, which contributes to
25-30%.25 Our study aligns with this pattern, with
SVT being the predominant contributor (62.5%, 5/8). While fetal
arrhythmias are typically isolated findings, around 5% of cases may
also involve congenital heart diseases.26,27 In our
study, all identified tachyarrhythmias were isolated without associated
SHD or tumors.
The presence of hydrops also significantly influences management and
outcomes, as it indicates an impact on the cardiovascular system,
reducing ventricular filling and cardiac output.28 In
this study, hydrops fetalis was observed in 50% (4/8) of fetal
tachyarrhythmia cases. The primary goal of fetal therapy is to achieve
the prevention or resolution of hydrops either through conversion to
sinus rhythm or ventricular rate control.29,30Transplacental administration of antiarrhythmic drugs is a commonly
employed and effective approach, with the primary aim of preventing or
resolving hydrops.23,24 Although no standardized
protocol exists for drug selection or doses, successful outcomes have
been documented. However, the decision on in utero or postnatal
treatment is challenging, with the effectiveness of both approaches
well-established.31 While intrauterine treatment is
highly effective, postnatal treatment remains a viable option
particularly in cases when imminent delivery is crucial.
Digoxin is widely accepted as a first-line antiarrhythmic
drug.24 Sotalol, flecainide, and amiodarone serve as
secondary options when digoxin proves ineffective in achieving
conversion to sinus rhythm.32 However, studies
indicate that for fetuses with hydrops, digoxin’s limited placental
transfer hampers its effectiveness.33 Therefore, for
cases involving hydrops, especially in fetal treatment, it is
recommended to initiate sotalol or flecainide, both of which exhibit
good placental transfer abilities.31,34 In our study,
the combination of digoxin and flecainide was introduced in the cases
which had associated hydrops, encompassing three instances of SVT and
one case of JET. All these cases reverted to sinus rhythm along with
resolution of the hydrops, accounting for 50% of the case of fetal
tachyarrhythmias. Digoxin monotherapy was initiated in two isolated
cases of SVT and once case of atrial flutter. Successful reversion to
sinus rhythm was achieved in the case of atrial flutter. However, in SVT
cases, monotherapy with digoxin did not result in reversion,
necessitating the addition of other antiarrhythmic agents in both
instances.
Thus, the study underscores the prevalence of SVT in fetal
tachyarrhythmias and the pivotal role of hydrops in treatment decisions.
While much of the literature often compares digoxin versus flecainide
and explores stepwise approaches to managing SVT, there are limited case
studies delving into the initiation of combined digoxin and flecainide
as a first line treatment, particularly in cases involving
hydrops.35,36 The successful application of this
combined therapy in our study suggests a potential shift in the
treatment paradigm and proposes it as a viable first-line option for SVT
with hydrops. However, further studies with larger sample sizes are
necessary to validate the findings and it is crucial to exercise caution
and make thoughtful selections of antiarrhythmics tailored to the unique
characteristics of each case.
VT is a rare fetal arrhythmia, constituting only 1–2% of
cases.25 Optimal therapy remains unclear due to its
rarity. Current literature suggests maternal intravenous magnesium
therapy as a first-line treatment for sustained VT.37Additional measures, such as intravenous lidocaine, oral propranolol, or
oral mexiletine, are recommended alongside
magnesium.32,37,38 In cases related to isoimmunization
or myocarditis, dexamethasone and intravenous immunoglobulin infusion
have been employed.39 In this study, we encountered
one case of VT with prolonged QT, where treatment with IV magnesium
sulphate followed by oral propranolol was initiated. While the rhythm
was controlled with small recurring episodes, the baby succumbed to
neurological complications 3 hours after birth. Hence, the study
highlights the rarity of fetal VT, emphasizing the challenges in
therapeutic strategies and the need for further research to establish
standardized protocols. Beyond clinical aspects, the study suggests
delving into the genetic and molecular factors associated with fetal VT,
potentially leading to personalized management strategies based on
identified markers. The impact of early VT diagnosis, evaluation of
maternal and fetal risk factors, and a detailed analysis of neurological
complications constitute key facets of this multifaceted approach.