Background: An interatrial communication is present in most neonates. The majority are considered the “normal” patency of the oval foramen, while a minority are abnormal atrial septal defects. Differentiation between the two with transthoracic echocardiography may be challenging, and no generally accepted method of classification is presently available. We aimed to develop and determine the reliability of a new classification of interatrial communications in newborns. Methods and Results: An algorithm was developed based on echocardiographic criteria from 495 newborns (median age 11[8;13] days, 51.5% females). The algorithm defines three main categories: patency of the oval foramen, atrial septal defect, and no interatrial communication as well as several subtypes. We found an interatrial communication in 414 (83.6%) newborns. Of these, 386 (93.2%) were categorised as patency of the oval foramen and 28 (6.8%) as atrial septal defects. Echocardiograms from another 50 newborns (median age 11[8;13] days, 36.0% female), reviewed by eight experts in paediatric echocardiography, were used to assess the inter- and intraobserver variation of classification of interatrial communications into patency of the oval foramen and atrial septal defect, with and without the use of the algorithm. Review with the algorithm gave a substantial interobserver agreement (kappa = 0.66), and an almost perfect intraobserver agreement (kappa = 0.82). Without the use of the algorithm, the interobserver agreement between experienced paediatric cardiologists was low (kappa = 0.20). Conclusion: A new algorithm for echocardiographic classification of interatrial communications in newborns produced almost perfect intraobserver and substantial interobserver agreement. The algorithm may prove useful in both research and clinical practice.

Background Mitral valve abnormalities (MVA) include mitral valve regurgitation (MR), mitral valve prolapse (MVP), Barlow's mitral valve disease, and parachute MV. The prevalence of MVA has yet to be determined in an unselected population of newborns. Objective To determine the prevalence of MVA in unselected newborns and to assess the left ventricular (LV) structure and function in the neonatal heart with MR. Methods Transthoracic echocardiography (TTE) was performed within 28 days after birth in unselected neonates consecutively included in a prospective, multicenter, population-based study (2016–2018 (n=25,751)). TTE's were systematically reviewed for MR, MVP, Barlow's MV disease, and parachute MV. In a subgroup of 400 newborns with MR, the regurgitation was further classified as either traceable MR, mild MR, or moderate/severe MR based on the ratio of the trans-mitral jet in systole over the diastolic filling duration using M-mode in the 4-chamber view of the LV. Results Of 25,751 included newborns, we found a prevalence of MVA of 26.7%. (6,883/ 25,751). The prevalence of MR was 26.2%, MVP was 0.35%, Barlow's disease was 0.13%, and parachute mitral valve was 0.027%. MR was more frequent in females compared to males (50.4 vs 48.2%, p<0.01). Newborns with MR had enlarged left atrial diameter (11.91±2.03 mm vs 11.53±2.02 mm, p<0.01) and LV end-diastolic and end-systolic diameter (LVIDd 19.98±1.88 mm vs 19.87±1.83 mm, p<0.01, LVIDs 13.48±1.47 mm vs 13.31±1.41 mm, p<0.01), thicker LV posterior wall (2.19±0.60 mm vs 2.05±0.52 mm, p<0.01), increased early and atrial mitral inflow velocities (MV E velocity (0.65±0.14 m/sec vs 0.61±0.13 m/sec, p<0.01), MV A velocity (0.60±0.13 m/sec vs 0.57±0.13 m/sec, p<0.01)), but lower fractional shortening (32.54±4.22% vs. 32.96±4.17%, p<0.01) as compared to newborns without MVA. In subgroup analysis MR severity was classified as traceable in 44% (175/400) of cases, mild MR in 52% (209/400) of cases and moderate/severe MR in 4% (16/400) of cases. Comparing traceable MR with moderate/severe MR (19.48±1.88 mm vs 20.96±2.64 mm, p=0.01) and comparing mild MR with moderate/severe MR (19.85±1.92 mm vs 20.96±2.64 mm, p=0.04) showed significant increases in LV end-diastolic diameter. Conclusion Over one fourth of all newborns had a MV abnormality of which mitral regurgitation accounted for the vast majority. The presence of MR was associated with asymmetric LV remodeling and discrete changes in LV function. Subgroup analysis revealed that increment in MR severity was primarily associated with an increase in LV end-diastolic diameter. Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Herlev-Gentofte Hospital

Introduction Patency of the oval foramen (PFO) and atrial septal defects (ASDs), i.e. interatrial communications, have been reported to be present in 24–92% of newborns. For isolated ASDs, the reported prevalence varies from 0.3–2.4 per 1000 livebirths. This broad range partly reflects the absence of a clear and universal clinical classification of interatrial communications. On this basis we have recently proposed a clinically applicable echocardiographic algorithm for classification of interatrial communications (figure 1), which proved superior to standard assessment by experts in terms of inter- and intraobserver agreement. Purpose To determine the prevalence of interatrial communications in newborns. Methods Echocardiograms (TTEs) from newborns (0–30 days) included in a population study (N>25,000) were assessed/analyzed for interatrial communications according to the new algorithm and categorized into three PFO subtypes and three ASD subtypes. Results TTEs from 16,420 newborns were analyzed; 3,694 (22.5%) were excluded due to suboptimal image quality and 9 (<0.1%) were excluded due to concurrent severe congenital heart disease. Of the remaining 12,718 included newborns (median age 12 days [8; 15], 48.1% female), an interatrial communication was present in 10,033 (78.9%) cases; 9,274 (72.9%) cases were classified as PFO while 759 (6.0%) were classified as ASD. In the ASD group, 368 (48.5%) had a defect size ≥4 mm, 364 (48.0%) had multiple interatrial communications, and 27 (3.6%) had the defect located in the lower 1/3 part of the septum (figure 2). Conclusion An interatrial communication was present in almost 4 out of 5 newborns. ASD was diagnosed in 6% of the newborns and the prevalence of PFO was 12 times higher than the prevalence of ASD. Follow-up studies of these children are expected to provide clinically useful information on the long term structural and hemodynamic impact of these well categorized ASD and PFO subtypes. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Candy's Foundation, The Danish Children's Heart Foundation