We often get questions about issues facing post-Fontan individuals. To learn more about the Fontan surgery, as well as the research being done by the Todd and Karen Wanek Family Program for HLHS at Mayo Clinic, I talked to Dr. Frank Cetta. Along with being a pediatric and adult congenital cardiologist, he’s also the lead investigator on the world’s largest single-center database of Fontan patients. We discussed the nuts and bolts of the procedure, tips for preventing common complications, and hope for the future.
Q: For people new to the heart community or unfamiliar with congenital heart disease (CHD), can you start by giving us an overview of the Stage III surgery, or the Fontan, for HLHS patients?
A: In single ventricle CHDs, what happens before Fontan at the Stage II surgery, or the Glenn, is that the “blue blood” (blood that’s already circulated around the body and now has no oxygen left in it) from the arms, head, and neck gets connected directly into the pulmonary artery (PA) to go into the lungs. In a small baby, that’s more than half of the blood flow that normally goes to the right side of the heart. At the Fontan, we bring the rest of the blood from the lower part of the body, intestines, legs, everything below the diaphragm, directly into the PA.
In a patient with a single ventricle, you only have one ventricle to work with, so the ventricle is built to pump the blood to the body and not the lungs. The Fontan finishes off a complete bypass of the heart by putting in a big tube so that all the “blue blood” in the veins never really goes through the heart – it just goes from the inferior vena cava (IVC), through some fancy plumbing, and directly into the lungs. [see Image 1]
The procedure was first done in the late 1960’s, and there have been many variations over time. But something we’ve found over the years is that the Fontan circulation is not “normal” circulation. It has many effects on other organs in the body.
Most Fontan patients will get some form of Fontan-Associated Liver Disease (FALD) at some point, although we’re now seeing that some may even have it before the Fontan operation. The reason for FALD is what we call “elevated central venous pressure.” [see Image 2] The pressure in the Fontan tube is a lot higher than normal. In a normal IVC, the pressure is about half of what it is in a really good Fontan patient. So the best Fontan patient still has pressure in that tube above the liver that’s twice as high as normal.
Image 3 is a good example. Look at the bottom where there’s a big, black, 3-prong thing. That’s dye showing the blood flow going from the liver into the IVC. See how big those vessels are? Then you move up into the Fontan tube. See how small that conduit is? Then you get above it -- see how big the pulmonary arteries are?
It looks like three lanes of traffic trying to merge into one.
No wonder there’s congestion! You don’t need to be a rocket scientist to figure out why the liver is backed up. It’s a bottleneck right there. So the liver gets congested and blood flow starts backing up in the liver. That’s the road to Fontan-Associated Liver Disease (FALD). The blood flow back-up is called “hepatic congestion” which leads to fibrosis, or scarring. That can lead to cirrhosis which is irreversible damage to the liver. Some patients progress to what’s called “hepatocellular carcinoma,” or liver cancer, although that’s very rare (< 1%).
Q: What are some things that post-Fontan individuals can do to take care of themselves?
A: If you have a Fontan and you have liver disease, you don’t want to be drinking alcohol all the time because alcohol’s bad for the liver. That doesn’t mean you can’t have a glass of wine with dinner, it means no binge drinking, regular drinking, or excessive alcohol.
You also want to be immunized against the hepatitis virus because that affects the liver, and you can also have bloodwork done to make sure the vaccines were effective. There are some drugs, including Tylenol, that can be bad for the liver and you should avoid excessive amounts.
Sleep apnea, which causes people to snore and stop breathing at night, is another issue. That can elevate the pressures in your lungs, and that pressure gets transmitted back down through the Fontan conduit, and puts even higher pressure on the liver. So Fontan patients with sleep apnea should be treated for that.
Also, being obese and having a Fontan is a bad combination. Exercise increases Fontan longevity, so you want to be lean and get good exercise. It improves lifestyle, longevity, and reduces some of the liver and other organ problems. Studies have shown that Fontan patients who exercise more have better blood flow into the lungs. It helps the whole body and is really essential for Fontan patients.
Q: Are there additional factors that make people with CHDs more prone to obesity?
A: No. Part of it is that we, as physicians, told their parents when they were little to keep “little Johnny” at home. We didn’t want them to bang into people or do activities that might put too much strain on the heart. It was all well-intentioned, but we have exercise guidelines where certain activities and sports are not allowed – and a lot of that is not based on any data
There are certain things that are common sense. For example, if you have a mechanical valve and you’re on a blood thinner, you shouldn’t be into knife throwing or carpentry where you might cut your hands all the time. But you could still play basketball and be careful. For decades, we told parents to sit on these kids and not let them do anything – and that’s probably the biggest thing we’re trying to undo today.
Obviously all patients are different, but we have definitely erred on the conservative side. It’s the same with women getting pregnant post-Fontan. We used to say that no one should do it. While we do see risks to the mother and fetus with loss and pre-term delivery, there are some women who are able to become pregnant and keep themselves and the baby healthy. Prior to pregnancy, a thorough evaluation needs to determine risks for the individual patient so they can make an informed decision. (To learn more, read our earlier blog post.)
Q: So those are things that the patient can do. What can healthcare providers do?
A: When we look at Image 3 from earlier, it’s pretty obvious – we need to make that tube bigger. That tube was put in when this patient was three years old. Now they’re 23 and that tube is too small. Image 4 shows that picture again, then the next picture is after the patient had a stent placed in the cath lab. See how narrow that tube was to start? Then they made it much bigger with the stent. You need to get rid of obstructions and create more space for blood to flow easily. If a patient has liver disease, they should have a cath done so we can see if there’s anything that can be fixed with a stent.
There’s also a blood test – alpha-feto protein (aFP) – which is the blood test marker for liver cancer. That is useful because if it’s elevated, that usually indicates serious liver cancer. So we do check that one regularly on post-Fontan patients. And we use ultrasound, MRI, and CT imaging to look for suspicious liver nodules or tumors.
There are some drugs that are speculated to possibly help the liver: Spironolactone to decrease scarring in the liver; Sildenafil to lower PA pressure; Warfarin to thin the blood and prevent clots from forming in the liver and causing fibrosis and cirrhosis. But there are no large studies on these, so it’s just a lot of speculation at this point in time.
Thinking back to the images we looked at, part of the issue is structural. If you have a 3-year old and you put in a big tube (maybe 18-20mm conduit), it may be too big for a kid and they’ll form clots along the inside of it. So some have advocated going to smaller conduits (16mm or smaller) for small kids. But that’s short-sighted – it gives you the best flow dynamics physically for a little kid, but these tubes don’t grow. They’re made of Goretex, or sometimes a homograft of human tissue, so they don’t grow. An adult needs an 18-20mm connection, and if it’s smaller, we get the pictures above. That’s why the cath lab and stenting as people grow is so important.
Q: What’s on the horizon?
A: What if we could put a pump in the circuit? We could achieve two things with a pump: increase the pressure in the PA, and at the same time, decrease the pressure in the IVC so it goes down to a normal level and hopefully improves the liver function. That will likely be the biggest help for the liver because the biggest problem is congestion in the liver. There’s a lot of research currently being done – including here in the Wanek program – and there is hope, but it’s still in the early stages.
We also did a pilot study using stem cells to strengthen the heart, but that was for when the Fontan was failing and heart function was down. We don’t know if stem cells can improve liver function in any way, but things like pumps and stem cells are the future of post-Fontan care that our program is working on today.
Q: What’s the take-home message about FALD?
A: The biggest message today is early surveillance. We’re finding that many individuals actually go into the Fontan already having liver disease, which can be problematic because the Fontan just puts more pressure on the liver. So blood tests and ultrasound imaging are important before and after the Fontan, and maybe even prior to the Glenn, to make sure we catch any problems early.
But for general Fontan health, the message is – exercise, exercise, and more exercise!
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