Tachyarrhythmias
There were 8/41 cases of tachyarrhythmias. Among them, we identified 5/8 cases of fetal supraventricular tachycardia (SVT) (Figure 2)and 1/8 case each of ventricular tachycardia (VT), atrial flutter, and junctional ectopic tachycardia (JET). Among the SVT cases, 3/5 fetuses had presented with hydrops. In these cases, a combined treatment approach involving oral digoxin and flecainide was started. While successful restoration to sinus rhythm was observed in all cases (3/3), one patient opted for termination of pregnancy at 24 weeks due to persistent hydrops. The other 2/3 cases, with resolved hydrops and restored sinus rhythm, underwent regular follow-ups through ultrasound examinations. Elective LSCS was performed for one fetus at 39 weeks, and postnatal evaluations, including ECG and echocardiography, revealed normal results. The child was under cardiology follow up till one year and remained in good health. The second fetus was delivered vaginally at 38 weeks, and postnatal assessments showed normal cardiac function.
In the remaining 2/5 cases, the initial treatment involved the administration of oral digoxin. When the initial intervention did not produce a positive response, a secondary antiarrhythmic agent (flecainide) was introduced. In one case, sinus rhythm was successfully restored after the addition of flecainide, with one episode of relapse before stabilization. The baby was delivered by LSCS at 38 weeks, maintaining a normal cardiac rhythm postnatally. However, in the other case, despite the combined use of flecainide and digoxin, persistent tachycardia was observed. Subsequent echocardiography revealed moderate pleural effusion with cardiomegaly. Emergency LSCS was performed at 36 weeks due to impending heart failure, and adenosine was administered postnatally to manage persistent tachycardia. Despite an initial positive response, subsequent relapse and deterioration occurred, leading to death on postnatal day 3.
Additionally, we encountered one case of JET with features of hydrops fetalis, referred at 24 weeks for fetal tachycardia (Fetal heart rate (FHR) 170–180 bpm) The fetal heart exhibited structural normalcy, with regular rhythm and 1:1 AV conduction, yet minimal heart rate variability. Spectral Doppler revealed increased retrograde flow during atrial systole in the ductus venosus and hepatic and pulmonary veins. Transplacental digoxin and flecainide were administered, resulting in the conversion to sinus rhythm after 6 weeks of treatment. Hydrops fetalis and retrograde flow in veins resolved, although ventricular filling remained monophasic. The fetus was delivered by LSCS at 38 weeks, with postnatal ECG and echocardiography showing normal results and infant maintaining sinus rhythm till postnatal day 5 and was discharged.
In one case, atrial flutter with an atrial rate of 460bpm and ventricular rate of 230 bpm was identified at 36 weeks of pregnancy in a patient with normal prenatal history. Although there was mild tricuspid valve regurgitation and minimal pericardial effusion, no evident cardiac structural anomaly, atrial enlargement, or hydrops was observed. After discussing management options, prognosis, and postnatal outcomes, the patient opted for medical management and was initiated on digoxin, resulting in a reversion to sinus rhythm after 3 days. An emergency LSCS was performed at 37 weeks due to breech presentation and premature rupture of membranes (PROM). The patient delivered a vigorous baby weighing 2.8 kg, but the infant experienced moderate pulmonary hypertension, requiring continuous positive airway pressure (CPAP). Postnatal echocardiography showed mild tricuspid regurgitation and a patent foramen ovale. The infant is currently in sinus rhythm and undergoing cardiology follow-up.
In another instance, ventricular tachycardia was diagnosed at 37 weeks of gestation in a patient who presented with decreased fetal movements for one day but otherwise uneventful antenatal period. Fetal echocardiogram showed VT with a ventricular rate of 240 bpm compared to an atrial rate of 130 bpm. The ECG displayed a polymorphic pattern with a prolonged QT interval. Maternal Anti-Ro/La antibodies were negative, and both parents had normal echocardiograms. An intravenous magnesium sulfate infusion with a loading dose of 4 gm followed by a maintenance dose of 1g/h was initiated to gain rapid control of the fetal arrhythmia and continued for 48 hours. The fetal VT resolved after 10 hours of magnesium sulfate commencement. Propranolol was administered after 48 hours at a dose of 80 mg three times daily, with intermittent relapses noted before the rhythm ultimately reverted to normal. Spontaneous labor occurred, and the patient delivered at 38 weeks of gestation. The newborn, however, exhibited poor Apgar scores, leading to NICU admission. The baby experienced severe encephalopathy, hyperkalemia, and acute kidney injury, ultimately succumbing 3 hours after birth. Genetic testing was not pursued as parental consent was not obtained.