Discussion

Fetal and neonatal ventricular tachycardia is a rare diagnosis that can range in severity from benign to life-threatening. ^{Reference De Rosa, Butera and Chessa2–Reference Strasburger and Wakai4} The management varies based on the severity of symptoms, age of presentation, and haemodynamic status. ^{Reference Wang, Zhu and Hamilton10} In our study, the clinical outcomes of both fetal and neonatal ventricular tachycardia were largely good with only a single fetal case developing hydrops related to evolving restrictive cardiomyopathy.

Ventricular tachycardia in fetuses and neonates has been reported in the presence of viral myocarditis, cardiomyopathies, cardiac tumours, anti-Ro antibodies, channelopathies, and abnormal electrolytes. ^{Reference Jaeggi and Ohman3,Reference Strasburger and Wakai4,Reference Karpawich, Pettersen and Gupta13,Reference Sacchetti, Moyer and Baricella24} In our study, 40% of fetuses and 62% of neonates had coexistent structural heart disease and this includes one fetal case of cardiomyopathy which may have been a contributing factor to ventricular tachycardia development. ^{Reference Kilic, Celiker and Karagoz6–Reference Iwamoto8}

Fetal ventricular tachycardia may become life-threatening if there is evolution of fetal hydrops. ^{Reference Jaeggi and Ohman3–Reference Simpson, Allan, Hornberger and Sharland5} However, proper management may reduce fetal death to less than 10%. ^{Reference Simpson, Allan, Hornberger and Sharland5} In this study, the one fetus that died had evidence of restrictive cardiomyopathy, which is known to carry a poor prognosis. ^{Reference Chiu, Wu and Lu1} Neonates with ventricular tachycardia may present with poor cardiac function and in rare cases this might lead to demise. ^{Reference Batra and Balaji7,Reference Iwamoto8} As suggested by the present case series, the majority of neonatal ventricular tachycardia, however, is benign and if accurately diagnosed and managed, the outcome may be quite favourable. ^{Reference Chiu, Wu and Lu1,Reference Iwamoto8}

While neonatal ventricular tachycardia relies on well-defined electrophysiologic features on ECG, ventricular tachycardia in the fetus is indirectly inferred when there is tachycardia with faster ventricular rate relative to atrial contractions, or A-V dissociation. Occasionally, fetal ventricular tachycardia may be associated with A-V association, but differentiating the latter from supraventricular tachycardia with 1:1 ventricular-atrial or atrial-ventricular contractions may be difficult. Furthermore, differentiating fetal ventricular tachycardia from junctional tachycardia can be very challenging and should be confirmed after birth (Figure 4). The presence of intermittent ventricular ectopy can be informative in this context and lead to the suspicion of ventricular tachycardia. ^{Reference Simpson, Allan, Hornberger and Sharland5,Reference Wang, Zhu and Hamilton10} Suspected fetal ventricular tachycardia should prompt exclusion of structural or functional fetal heart disease and acquisition of 12-lead ECGs in both the mother and father of the fetus given the possibility of a channelopathy, which may help tailor treatment and ensure ongoing surveillance and treatment of the affected parent. ^{Reference Simpson, Allan, Hornberger and Sharland5}

Figure 4. Differntiating VT from JET A: This 34-week fetus presented in tachycardia initially with 1:1 ventricular (arrow) to atrial (A) relationship at 180-190 bpm. When not in tachycardia, the baby was having ventricular trigeminy (P) and otherwise normal A-ventricular (V) synchrony. B: The ventricular ectopy was confirmed by the simultaneous superior vena cava (SVC)-ascending aortic Doppler interrogation with SVC a wave reversal and forward flow through the aorta are shown above the baseline and forward flow through SVC below the baseline. Normal atrial (A) and ventricular (V) contractions are shown, but with a premature ventricular contraction (P) occurring during an atrial contraction, the AV has a very high velocity in keeping with a cannon A wave (atrial contraction against a closed tricuspid valve). C: In addition to the presence of premature ventricular contractions out of tachycardia, the fetus also demonstrated ventricular (arrow)-atrial (A) dissociation at one point in tachycardia with a clearly faster ventricular rate.

In fetal ventricular tachycardia, use of transplacental antiarrhythmic medication has been recommended in cases with recurrent and prolonged tachycardia or in the presence of hemodynamic compromise. ^{Reference Strasburger and Wakai4,Reference Simpson, Allan, Hornberger and Sharland5,Reference Wang, Zhu and Hamilton10} However, close surveillance is mandated for both treated and untreated fetuses. ^{Reference Wang, Zhu and Hamilton10}

In the current cohort, we were able to manage 4 of the 5 fetal cases with no need for early delivery. One fetus did not have rhythm normalisation until flecainide was added to the initial amiodarone therapy. Jaeggi et al. ^{Reference Jaeggi and Ohman3} suggested that beta-blockers is the mainstay to treat fetal ventricular tachycardia; however, as propranolol has poor transplacental transfer, if not clearly reducing the ventricular tachycardia, moving to other medications, such as amiodarone, sotalol, and flecainide, after excluding long QT syndrome, may be necessary to achieve control. Further assessment is needed in these cases to role out long QT by getting detailed family history and ECG for the parents and genetic testing if needed. ^{Reference Batra, Silka and Borquez32}

In the neonatal period, we initially utilised intravenous medications in half and oral in the other half of our patients. The choice of antiarrhythmic was based on the stability of the neonates and the suitability of using oral or intravenous medication. Wang et al. ^{Reference Isik, Celik and Kavurt9} reported beta-blockers as first-line treatment for paediatric ventricular tachycardia with good outcomes, and others have reported the successful use of slow infusion amiodarone as a second-line treatment in this age group. ^{Reference Lulic Jurjevic, Podnar and Vesel11,Reference Sacchetti, Moyer and Baricella24,Reference Dai, Yin and Yang29} For all fetal and neonatal cases in the current report, successful therapy was achieved prior to discharge. Levin et al. ^{Reference Lulic Jurjevic, Podnar and Vesel11} reported that infants with ventricular tachycardia have promising outcomes, with follow-up needed for most of the cases up to 3 years. Similarly, our study has found that all neonatal ventricular tachycardia resolved within the first year with a median follow-up of 33 months with no recurrence up to three years from the last episodes (Table 1).