Background: Left ventricular noncompaction (LVNC) is characterized by excessive trabeculations of the LV and may be associated with reduced systolic function or severe adverse outcomes. Several aspects remain to be elucidated; there is controversy to whether LVNC cardiomyopathy is a distinct cardiomyopathy caused by failure of the spongy fetal myocardium to condense during fetal development or acquired later in life as a morphological trait associated with other types of cardiomyopathy; the prevalence in unselected populations is unknown and the distinction between normal variation and pathology remains to be defined. In this study, we aimed to determine the prevalence of LVNC and the association to LV systolic function in a large, population-based cohort of neonates. In addition, we assessed the normal ratio of noncompact to compact (NC:C) myocardium in 150 healthy neonates. Methods: Echocardiographic data were prospectively collected in the population study Copenhagen Baby Heart Study. The ratio of NC:C was measured in 12 ventricular segments. LVNC was defined as NC:C ≥2 in at least one segment. Neonates with LVNC were matched 1:10 to controls on sex, gestational age, and weight and age at the examination day. Results: In total, 25 590 neonates (52% males, median age 11 [interquartile range, 7–15] days) underwent echocardiography. Among 21 133 with satisfactory visualization of ventricular segments, we identified a prevalence of LVNC of 0.076% (95% CI, 0.047–0.123). LV ejection fraction was lower in neonates with LVNC compared with matched controls (median 49.5 versus 59.0%; P <0.0001). In neonates with otherwise healthy hearts, the median NC:C ratio ranged from 0.0 to 0.7 and the 99th percentiles from 1.0 to 1.9 for each of the 12 segments. Conclusions: The prevalence of LVNC based on neonatal echocardiography was 0.076%. LVNC was associated with lower LV systolic function. The findings in normal newborns support the cutoff NC:C ≥2 as an appropriate diagnostic criterion. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02753348.

Atrial septal defect (ASD) is characterized by a left-to-right shunt causing dilatation of the right atrium and right ventricle as well as pulmonary hyperperfusion. The detection of ASDs often occurs late in childhood or adulthood. Little is known about cardiac structure and function in neonates with ASD.We analyzed neonatal echocardiograms from the Copenhagen Baby Heart Study, a multicenter, population-based cohort study of 27,595 neonates. We included 716 neonates with secundum-type ASDs and matched them 1:1 on sex and age at examination with neonates without ASD from the same birth cohort. Neonates with an ASD (median age 11 days, 52% female) had larger right ventricular (RV) dimensions than matched controls (RV longitudinal dimension end-diastole: 27.7 mm vs. 26.7 mm, p < 0.001; RV basal dimension end-diastole: 14.9 mm vs. 13.8 mm, p < 0.001; and RV outflow tract diameter 13.6 mm vs. 12.4 mm, p < 0.001). Atrial volumes were larger in neonates with ASD compared to controls (right atrial end-systolic volume: 2.9 ml vs. 2.1 ml, p < 0.001; and left atrial end-systolic volume 2.0 ml vs. 1.8 ml, p < 0.001). Tricuspid annular plane systolic excursion was larger in neonates with ASD than in controls (10.2 mm vs. 9.6 mm, p < 0.001). Left ventricular dimensions and function did not differ between neonates with ASD and controls. In conclusion, ASDs were associated with altered cardiac dimensions already in the neonatal period, with larger right ventricular dimensions and larger atrial volumes at echocardiography within the first 30 days after birth.ClinicalTrials.gov Identifier: NCT02753348 (April 27, 2016).