Low mortality in fetal supraventricular tachycardia: Outcomes in a 30-year single-institution experience

Low mortality in fetal supraventricular tachycardia: Outcomes in a 30-year single-institution experience

O’Leary ET, Alexander ME, Bezzerides VJ, Drogosz M, Economy KE, Friedman KG, Pickard SS, Tworetzky W, Mah DY.

J Cardiovasc Electrophysiol. 2020 Feb 26. doi: 10.1111/jce.14406. [Epub ahead of print]

PMID: 32100356

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Take Home Points

  • Sustained fetal SVT (defined as tachyarrhythmia present for greater than or equal to 50% of the diagnostic fetal echocardiogram) maybe associated with significant morbidity but a low mortality.
  • The optimal management strategy for sustained fetal SVT remains unclear – multiple antiarrhythmic agents are required in over half the cases.
  • Sustained fetal SVT in fetuses with a structurally normal heart can be effectively managed with transplacental drug therapy with minimal risk of intrauterine fetal demise.
  • Accurate characterization of the arrhythmia mechanism on fetal echocardiogram is important, as a confident diagnosis of atrial flutter is unlikely to become a chronic arrhythmia that requires long term AAD therapy.
  • The presence of moderate to severe ventricular systolic dysfunction in fetuses with SVT is likely associated with postnatal SVT.

Dr. Khyati Pandya (Memphis, TN)
Commentary by Dr. Khyati Pandya (Memphis, TN) Congenital and Pediatric Cardiac EP section editor: Mah et al describe a retrospective cohort study of fetuses with a structurally normal heart, diagnosed with sustained SVT between 1985 and 2018.


FIGURE 2: First line antiarrhythmic drug choice stratified by year of diagnosis
No cases of IUFD were observed in the study cohort. AVRT was the most common arrhythmia mechanism, responsible for approximately two of three of cases followed by AFL which was seen in one of four, as reported in previous studies.
Digoxin was popular as a first line antiarrhythmic agent throughout the time period of the study (fig 2). The arrhythmia management strategy resulted in overall survival of 97% and overall treatment success rate of 82%, however, it was noted that digoxin monotherapy did not provide consistently effective rhythm or rate control in the majority of cases, especially AVRT (36% conversion to sinus rhythm). This was in contrast with previously published studies where Digoxin was reported to convert AVRT to sinus rhythm in 57% and 69% of the patients. Their discrepant finding was attributed to practice variation with respect to digoxin dose, the timing of digoxin initiation, and the decision by the obstetrical team to deliver the fetus. 62% fetuses initially treated with digoxin monotherapy ultimately received a second line AAD regimen. The most common second line AAD regimen was the combination of digoxin and flecainide
As noted by the authors, the study had limitations for the following reasons:

  • Only univariate associations were calculated due to the small sample size of the cohort which precluded their ability to adjust for potential confounding variables.
  • PJRT and EAT made up the minority of cases, making it difficult to draw significant conclusions from the data.
  • Data were collected via retrospective chart review spanning three decades with variable documentation in the electronic medical record for certain clinic variables, specifically drug dosing.

The data represented in the study was thorough and exhaustive, highlighting the preferential use of Digoxin as a first line agent over three decades. The dosing regimen of various antiarrhythmic agents was elaborated. However, one of the potential challenges is accurate diagnosis of the SVT mechanism, that is often elusive on a fetal echocardiogram. Diagnosis and treatment of sustained SVT earlier in gestation can potentially help in averting progression to hydrops and premature delivery by decreasing the cumulative arrhythmia burden and thereby, the likelihood of ventricular dysfunction. More studies, of a prospective and multi-institutional nature are required to define the utility of newer available antiarrhythmic agents in the fetal and neonatal population, with a focus on safety and efficacy of antiarrhythmics in earlier stages of gestation for both the mother and the fetus.