Posts Tagged ‘Tricuspid Valve’

The Dirty Little Secret of HLHS

October 1, 2009

She didn’t even have a name for it.

When Dr. Helen Taussig wrote Congenital Malformations of the Heart in 1947, she described one malformation as “Atresia or marked hypoplasia of the aortic orifice prevents the expulsion of blood from the left ventricle in the normal manner.” Taussig described several variations of the defect – actually different defects, later grouped together under the same deadly name – but could offer no treatment suggestions. Her Tetralogy of Fallot (ToF) patients could at least squat and get some temporary relief; children cursed with this malady died in less than one week. The left side of the heart wasn’t damaged as much as it just wasn’t there.

It wasn’t until 1958 that Dr. Jacqueline Noonan and Dr. Alexander Nadas named the group of defects Hypoplastic Left Heart Syndrome (HLHS). Hypoplastic comes from the root word hypoplasia, which means “small”.

But having a name for it didn’t make it any less deadly as HLHS continued to claim 100% of its victims. This sad story continued until 1985, when the first successful infant heart transplant took place.

At about the same time the Norwood Procedure was developed. Originally designed as one operation (which consistently failed) the procedure was soon split into two heart operations – and eventually three – which seemed to work. HLHS children now had a chance. Obviously long term survival rates aren’t known yet, but approximately 70% survive the three surgery protocol.

And thats when the dirty little secret of HLHS showed itself: While survival rates for the three operation procedure may be in the 70% range, getting from Stage I to Stage II is the hardest step.

The goal of the Stage I operation is to make the Right Ventricle do the job of the defective Left Ventricle – getting the blood to the body. With all of the blood flowing through the right side of the heart, that side is subject to higher flow pressures than it usually receives. A lot higher. In a defect in which the entire left side of the heart is damaged, a successful outcome usually depends on the Tricuspid Valve – located on the right side of the heart.

The inital results were confusing. The Norwood worked – then it didn’t. There didn’t seem to be any rhyme or reason to it, no way to predict outcomes. The surgery itself worked, but too often the results¬† seemed to be as random as a roll of the dice. The answer was the Sano Shunt, invented by Japanese surgeon Shunji Sano – a direct connection from the Right Ventricle to the Pulmonary Artery through a Gortex conduit. (this sounds redundant, but the Pulmonary Artery is normally disconnected from the ventricle in the Stage I operation). Studies showed that survival chances with the Modified Norwood was 11 times greater than with the Classic Norwood.

And now it is time to turn the tables – we’ve got a nasty little trick of our own. Heart defects have to start somewhere… at some point in fetal development, there must be one isolated problem that seems to “snowball” into something bigger as time passes. If we could find that one little problem and repair it then, maybe we can stop the snowball before it gets too big. A pretty cool idea, and maybe one day…

Someday…

A study released Monday (September 28, 2009) revealed that for seven years, doctors at several hospitals in Boston and Harvard Medical School have been detecting Aortic Stenosis in fetuses. Fetal Aortic Stenosis is a snowball; it usually becomes HLHS as the fetus develops.

70 future HLHS patients underwent surgery while still in the womb – a needle was inserted into the mother’s abdomen, passed into the fetus, and into the heart of the unborn child. A small balloon was used to enlarge the abnormally small Aortic Valve. 51 of the procedures were considered successful… and 30% (17 children of the 51) were born with two functional ventricles. That’s 17 children who won’t have HLHS.

Mark September 28¬† on your calendar… that was the day that the CHD world changed forever.

Moving Your Valves Around

September 29, 2009

Don’t be surprised to hear about more CHDers having the Ross Procedure to repair a damaged Aortic Valve. Invented by British surgeon Donald Ross in 1967, the Ross procedure is performed on roughly 1500 patients each year.

During the Ross Procedure, both the Aorta and the Pulmonary Artery are clamped and cut near the junction with the heart. The damaged Aortic Valve is then removed and discarded. The Pulmonary Valve is then removed and sewn into the Aortic Valve’s place. A frozen Pulmonary Valve (previously removed from a cadaver) is then reanimated and sewn into the opening left by the original Pulmonary Valve. In the final step, the Aorta and the Pulmonary artery are then sewn back into place. If this is a little confusing, here’s a helpful diagram.

It does seem a little strange – if you recall our memory trick for remembering the proper order of the valves, it’s “Three People Might Agree” – blood flows normally through the Tricuspid Valve, then the Pulmonary Valve, out to the lungs and back to the heart; through the Mitral Valve, and finally through the Aortic Valve and out to the body. T – P – M – A, or Three People Might Agree. If you follow the route after a Ross Procedure, you go through the Tricuspid, Pulmonary, Mitral, and another Pulmonary… Three People Might People! That makes no sense! But it works.

New research has shown that the Ross Procedure has a high survival rate, and the cadaver valve works well – after 20 years, 80% of Ross patients did not need replacement of either Pulmonary Valve. The operation also has the advantage of growing with the patient (great for children!) and no need for anticoagulation… Goodness knows, I wish I didn’t have to have an INR test ever few weeks!