Utility of Surveillance Ambulatory Rhythm Monitoring in the Pediatric Fontan Population

Utility of Surveillance Ambulatory Rhythm Monitoring in the Pediatric Fontan Population

Taylor P Saley 1 2Neil D Patel 1 2Yaniv Bar-Cohen 1 2Michael J Silka 1 2Allison C Hill 3 4

PMID: 33963437

Pediatr Cardiol. 2021 Aug;42(6):1442-1448. doi: 10.1007/s00246-021-02630-0. Epub 2021 May 7.


Take Home Points:

  • In Fontan patients aged 3-21 years, retrospective review of arrhythmias noted on ambulatory rhythm monitoring (ARM) was performed in 83 Fontan patients between 2014-2018.
  • Patients with arrhythmias has a median age of 10.9 and patients without had a median age of 8.8 years (P-wave 0.5).
  • Surveillance only ARM was performed in 56% of cases and overall 33% of patients had an arrhythmia (defined as >1st degree AVblock, complex ventricular ectopy, accelerated junctional rhythm, sinus node dysfunction, or supraventricular tachycardia), with 26% of surveillance-only ARM’s demonstrating arrhythmias.
  • Arrhythmias were present more-often in females (48% vs 23%), p-value <0.01), those with systemic RV’s (46% vs 19%, p-value <0.01), and longer QRS durations (100 vs 94ms, p-wave 0.04)

Dr. Daniel Cortez

Commentary from Dr. Daniel Cortez (Sacramento, CA, USA), Congenital and Pediatric Cardiac EP section editor.

The American Heart Association (AHA) has also recognized the progressive nature of multi-organ dysfunction in the Fontan population and published a 2019 statement encouraging routine cardiovascular surveillance (3).


Similar to a lot of institutions, most patients didn’t have rhythm monitoring performed:


The types of ARMs included were either Zio Patch (iRhythm Technologies, Inc., San Francisco, California) or 24 h Holters. Each ARM was categorized as surveillance (performed in accord with the care plan and in the absence of other clinical concerns) or clinically indicated (performed outside of the surveillance plan due to provider concern for arrhythmia based on symptoms, abnormal ECG, or history of prior arrhythmia). 


Clinically indicated ARM’s were compared to those with just surveillance. The results of a difference between surveillance and clinical arrhythmias is not too surprising, however, what was interesting was that 1/4th of surveillance only ARM’s demonstrated a true arrhythmia.



Twenty-seven (33%) patients and 52 (37%) ARMs were positive for arrhythmia.

Sixty-eight discrete arrhythmias were present including 23 (33.8%) cases of SVT, 20 (29.4%) of complex ventricular arrhythmias, 18 (26.4%) of accelerated junctional rhythm, 4 (5.9%) episodes of Wenckebach, and 3 (4.4%) episodes of sinus node dysfunction. The only peculiarity here is differentiating accelerated junctional rhythm versus episodes of sinus node dysfunction, as Fontan patients with accelerated sinus junctional rhythms typically have sinus node dysfunction, thus that last number is slightly misleading.


Based on results, increased surveillance or medication change occurred in 31% of patients.


It is interesting as well that surveillance (occult) screening identified 10 episodes of SVT and made up 44% of arrhythmias noted on surveillance (occult screening) as compared to clinical screening which demonstrated more symptomatic accelerated junctional patients than SVT patients.



The authors describe that “the Australian and New Zealand Fontan Registry reported that 15% of all Fontan patients experienced arrhythmic events prior to 16 years of age, whereas our study found that a much higher proportion (33%) of Fontan were found to have arrhythmias on ARM at an even younger age (median 10 years)”.


And astutely point out “arrhythmias are relatively common in the atrio-pulmonary Fontan population, with a 10-year arrhythmia free survival rate of only 70% [1011]. However, it is thought that extracardiac Fontan patients have a lower risk for arrhythmias with studies finding 0–11% of extracardiac Fontan patients of having arrhythmic events prior to 16 years of age [11]. Our study comprised almost exclusively of extracardiac Fontan patients and a younger cohort than what has been previously described, yet our findings indicate a higher incidence of arrhythmias” (33%).


The author’s point out in their limitations section that the current recommendation is to assess Fontan patients with an ARM every 2-3 years except during adolescence every 1-2 years is recommended.


In conclusion, this is an interesting study in the assessment of mostly extracardiac Fontan patients demonstrating asymptomatic arrhythmias, which may or may not cause hemodynamic concerns may be more likely present than what was previously thought. Clearly the retrospective nature of the article is limiting, but interesting, nonetheless.