Opening the atrial septum: the difference shows up only when it works

A baby with hypoplastic left heart and a sealed or nearly sealed atrial septum is in a particular kind of trouble. Blood returning from the lungs has almost nowhere to go. Teams have tried, for twenty years, to make a hole in that wall before birth. The 775-fetus summary already on this site looked across studies and could not show that atrial-septum procedures changed live birth or death after birth. A single-center paper, originally published on 1 September 2025, asks a sharper question than "did they try."

Who was in the room

Betul Yilmaz Furtun and colleagues reviewed fetuses seen from 2012 through 2024 with hypoplastic left heart syndrome, double-outlet right ventricle with mitral stenosis or atresia, or mitral valve dysplasia, plus a severely restrictive or intact atrial septum, who were evaluated for a fetal atrial septal intervention. Sixty fetuses met that description. Eighteen were judged extremely high risk and left out of the comparison. The paper is about the remaining 42. Twenty-five had the procedure. Seventeen did not. The authors report no significant difference in the baseline echocardiograms between those two groups.

That exclusion matters at a kitchen table. The 52-versus-29 comparison is not "every fetus with a sealed septum." It is the fetuses the team still considered candidates. The eighteen who were set aside are not hidden inside the higher number.

The split that changes the sentence

Of the 25 attempts, 18 were technically successful. Thirteen of those children were alive at the time of the report: six after the Glenn, six after the Fontan, one after a Ross. Of the seven attempts that did not succeed, the paper counts five deaths around the procedure itself and one fetal death later. It does not, in the abstract, account for the seventh by name, and this page will not invent that outcome.

Technical success rose as the team did more of them: 58 percent in the first 12 attempts, 85 percent in the last 13. The same center had already described, in 2019, using a thulium laser to puncture the septum before placing a stent. This 2025 paper reports the rise. It does not, in the published abstract, assign that rise to one instrument, so neither will we.

What happened to the lung picture

Twenty of the fetuses who had the procedure also had a fetal MRI. Fifteen of those twenty, 75 percent, showed the nutmeg-lung pattern, the imaging sign of a lung under back-pressure. Of the nine who had that pattern and then a second MRI after a technically successful opening, eight looked better. Among the thirteen survivors of a successful opening, eleven had catheter measurements before the Glenn or the Fontan, and every one of those eleven had a pulmonary vascular resistance under 3 Wood units. The paper prints that unit as "Woods." The number is the point: the lungs that could be measured were not stuck at the high resistance that makes the later operations impossible.

Eight of nine is a small count. It is a description of the fetuses who were imaged twice, not a promise that every nutmeg lung will clear.

What to ask, if this is the diagnosis

What this means for you: most fetal heart findings never reach this procedure. It is discussed when the left heart is too small and the wall between the atria will not let blood out of the lungs. If that is the scan in front of you, the useful questions are specific. Is this center offering the attempt, or referring for it. What is their recent technical-success rate, not their lifetime average: in this series the early attempts and the later ones were not the same procedure in practice. And if someone quotes a survival figure, ask whether it counts every attempt or only the openings that worked. The first figure in this paper is not significant. The second one is. Both are from the same operating room, and neither is a randomized trial.

The prognosis page still holds the longer view of hypoplastic left heart after birth. Nothing here replaces a conversation with the team that has the images.