Prevalence and prognosis of atrial septal aneurysm in high risk fetuses without structural heart defects

The aim of this study was to evaluate the prevalence and prognostic implications of the association between atrial septal aneurysm (ASA) and fetal arrhythmias in a population of high risk fetuses.

One thousand three hundred and two fetal echocardiograms performed during high risk pregnancies from the 17th to the 41st week of gestation were retrospectively evaluated for the presence of ASA and/or arrhythmias. An ASA was defined as redundant tissue extending at least halfway across the left atrium. Patients with an ASA were distinguished in two subgroups according to whether there was (subgroup 1) or was not (subgroup 2) cyclical contact of the atrial septum with the left atrial wall or with the mitral valve. Arrhythmias were documented during mono/two-dimensional echocardiography and Doppler evaluation.

Out of 1223 patients considered for the study, 93 (7.6%) fetuses had an ASA; among these 93 fetuses, 33 (36%) had premature atrial beats (p < 0.001). Ten of these patients were included in subgroup 1, and 7 of them (70%) exhibited premature atrial beats (p = 0.016 vs subgroup 2). No arrhythmias other than premature atrial beats were observed in these patients. None of them received any therapy during observation. All of them developed a regular sinus rhythm within 3 months of life.

On the basis of these data, we can speculate that, if accurately searched for, ASA is often present (7.6%) and is likely to represent a mechanical stimulus for the generation of premature atrial beats. Indeed, our data show an important correlation between the degree of bulging and the presence of arrhythmias, supporting the hypothesis of a mechanical stimulus. However, the observed arrhythmias did not appear to be prone to degeneration. In conclusion, ASA observed during fetal life is often associated with premature atrial beats, which are apparently in direct relation with the degree of bulging of the atrial septum. On the other hand, an ASA almost invariably disappears at birth and is not associated with major arrhythmias.