P4644Distribution of newly defined subtypes of interatrial communications in 7,000 newborns from a general population study
Authors: Blixenkrone-Moeller E , Dannesbo S , Pihl C , Sillesen A.-S , Voegg O , Axelsson Raja A , Colan S , Mertens L , Vejlstrup N , Iversen K , Bundgaard H 
Published: October 2019

Abstract

Introduction
The prevalence of interatrial communications (IACs) (patent foramen ovale (PFO) or atrial septal defect (ASD)) in newborns has previously been reported to be between 24% and 92%. However, previous studies were generally small, and no universal classification of IACs exists. We proposed a new echocardiographic diagnostic algorithm developed in collaboration with a group of international experts to classify IACs into subtypes based on echocardiographic findings on transthoracic echocardiographic (TTE) images of the atrial septum in unselected newborns.

Purpose
To describe the distribution of the six newly defined subtypes of IACs in newborns based on the new diagnostic algorithm.

Method
Echocardiograms of newborns (age 0–30 days) consecutively included in a large, prospective population study (n=25,000) were analyzed using the new algorithm. The algorithm classifies IACs into three subtypes of PFO and three subtypes of ASD based on subxiphoid TTE findings considering the normal fetal development. The images were examined for colour Doppler signal possibly crossing the atrial septum, with or without acceleration, and with or without a visible communication on 2D. Furthermore, the size and morphology (channel-like structure or open hole) of a possible IAC as well as the number of communications were evaluated in determining the subtype of IAC according to the algorithm. The three subtypes of PFO were determined as follows: PFO1 were only detectable using colour Doppler; PFO2 had a channel-like structure visible on 2D; and PFO3 had a diameter of ≤3.4 mm and no channel-like structure. The three subtypes of ASD were determined as follows: ASD1 had a diameter of >3.4 mm; ASD2 was located in the inferior 1/3 part of the septum; and ASD3 had more than one IAC.

Preliminary results
As of 3 February 2019, 9,028 echocardiograms have been analyzed. A total of 2,026 (22.4%) were excluded due to poor image quality of the atrial septum. Of the 7,002 included echocardiograms, an IAC was detected on the TTE images in 85.9% of the newborns (median age 12 days [IQR 8; 15], 47.9% females). According to the algorithm, 78.7% of the newborns were classified as having a PFO (35.0% had a PFO1; 21.8% had a PFO2; and 21.9% had a PFO3) whereas 7.2% were classified as having an ASD (3.5% had an ASD1; 0.2% has an ASD2; and 3.5% had an ASD3) (see Figure 1).
Figure 1. Distribution of subtypes

Conclusion
An IAC was present in the vast majority of newborns aged 0–30 days. The most frequent PFO subtype was PFO1, which was only detectable by colour Doppler and was 1.6 times more frequent than the two other PFO subtypes, which had equal frequencies. The most uncommon ASD subtype was ASD2 which was located in the lower 1/3 part of the atrial septum and was 17.5 times less frequent than the ASD1 and ASD3 subtypes, which had equal frequencies.
(Figure 1: PFO: Patent foramen ovale, ASD: Atrial septal defect, IAC: Interatrial communication)

Acknowledgement/Funding
Danish Heart Association, Danish Children's Heart Foundation, Candy's Found., Toyota Found., Herlev-Gentofte Hospital Research Found., Gangsted Found.