Single Ventricle Alphabet Soup

When we first learned Luna’s heart was composed of just one ventricle, the only information I could find on her rare anatomical condition was for Hypoplastic Left Heart Syndrome (HLHS). Because of her unusual heart, bi-weekly echocardiograms at Children’s Boston became part of our regular pre-natal care. And each appointment, where I would sit in a darkened room for close to an hour and a half, while the cardiologist circumferenced my globe-like belly with a forceful probe; I would ask him, “but this baby doesn’t have HLHS?” Kindly, patiently, Dr. Brown would answer my anxious and continuous inquiries the same way each time: “No, this baby’s heart does not fall into the HLHS category of single ventricle formation.”

A recent blog post brought in several comments, many from other heart moms commiserating with me; welcoming us to their pack, Luna is HLHS too, they cheered.

But actually, Luna is not HLHS; she falls into her own unique category for single ventricle kids. Her own acronym still somewhat up for debate, but most professionals have settled on DORV/DIRV-or Double Outlet Right Ventricle/Double Inlet Right Ventricle.

I decided to ask Luna's New Hampshire cardiologist, Dr. Gauthier (Luna has two cards, one in Boston, and one closer to us in NH) for, oh, about the twelfth time how Luna differs from the HLHS kids. One of Dr. Gauthier’s biggest gifts to her patients (or in our case, to the parents of her patients) is her ability to craft the complicated and complex world of the various Congenital Heart Diseases into easily understood metaphors.

This is what she wrote:

“Luna best fits into a ‘single ventricle’ category. This is what it sounds like- for all intents and purposes, she did not divide her heart into two ventricles, and instead of one or the other ventricle being hypoplastic (small), she only formed one (her right), with both internal valves (mitral and tricuspid) entering into this chamber, and both outlets (aorta and pulmonary artery) arising from this chamber-- that is, it would have, if she had formed two outlets. Instead, she formed only one outlet valve, the aortic valve, and the other, the pulmonary valve, was "atretic"- like a door sealed shut- in her case, so poorly formed that it could not be pried open in any way (which can be done in some cases) but instead they had to find a way to surgically bypass this. So she fits into the "double inlet, doublet outlet right ventricle" category complicated by "pulmonary atresia.". This translates to a single ventricle accepting all inflow and pumping all outflow. To make things more complex, her heart formed pointing rightward instead of the normal leftward location, so she has "dextrocardia." And then last, her aortic valve did form, but instead of forming three leaflets, she has only two leaflets opening and shutting. This is the "bicuspid valve". The only significance to this at this stage is that it makes a little clicky sound when it opens but otherwise it works just fine.

HLHS and HRHS are different anatomically and the importance between those two as well as Luna's "single ventricle" version is in the way it is repaired and how much work has to be done to get the blood to flow out to the body. Luna is on the better end of the spectrum compared to HLHS on that front, although similar in that she really only has a right ventricle doing all the work to pump to her body. HRHS has the advantage in that the ventricle that does the pumping is a left ventricle, which is better designed for that purpose, but all three only use one ventricle to pump to the body and the blood is re-routed surgically to drain passively into the lungs (in other words, all three usually wind up with a version of a Fontan, but with varying types of surgery to get the blood to flow to the body and to the lungs).”