DECODED: The “Failing Fontan”

Ok y’all, I asked - you answered! So this one is for Nicole, who wanted to know more about the failing Fontan. 💗

The first time I heard the phrase “failing Fontan,” nobody sat me down and formally announced it. It arrived the way many frightening medical phrases do: sideways, a little too carefully, in fragments during a whispered conversation with my daughter’s cardiologist as we waited for her to wake up from a cath lab.

At the time, Aveline had been increasingly desaturated again and her venous pressures were running much higher than expected for her age and years since her Fontan. Her care team felt they needed to go into the cath lab to get a clearer picture of what was happening inside the circulation. The details of that cath are not the point here, but the part that matters here is this: over the years, her body had developed so many collateral vessels (extra blood vessels the body sometimes grows as a workaround when pressure or flow isn’t behaving nicely; apparently the body has its own rogue civil engineering department) that her team could no longer treat them one by one like some game of whack-a-mole and pretend that was the whole story. So the conversation had shifted from “we found one thing and fixed it” to something more like “we are now dealing with a system that is under strain, and the usual repair-by-repair approach isn’t enough anymore.”

After that last cath lab, her team pivoted to daily diuretics and tadalafil (a pulmonary vasodilator; it widens the blood vessels in the lungs to reduce pressure), aiming to bring her venous pressure down and slow the development of new collaterals. Not transplant, mind you, nor end-stage; management. And good Lord, what a phrase to sit with — because if, like me, you’re a parent hearing “failing Fontan” for the first time, it sounds brutally clear: the Fontan is failing, something is breaking, the next stop is transplant, the bottom has dropped out. I mean, I was spinning out when I heard the cardiologist mention it. I jumped in right away: ‘What what do you mean by that?’ Except that that’s not always what doctors mean; and also (frustratingly), doctors don’t all mean exactly the same thing when they say it.

Fun, right?! 🤦🏻‍♀️

So I’m going to try to decode the term itself for you, because we all know that fear loves vague language, and “failing Fontan” is about as vague as a phrase can get while still sounding like it arrived wearing steel-toed boots.

A Fontan circulation is not a normal circulation with a few architectural quirks; it’s a brilliant, life-saving, surgically engineered workaround for children born with one functional pumping chamber (a single ventricle) instead of the usual two. In a typical heart, the right ventricle pumps blood to the lungs. In a Fontan circulation, there is no dedicated pump to the lungs; blood from the body is routed directly into the pulmonary arteries and has to move through the lungs passively, pushed along largely by venous pressure. On its own, this is extraordinary… and it’s also weird as hell physiologically speaking, because the Fontan asks the body to do something bodies were never designed to do: move blood through the lungs without a proper sub-pulmonary pump.

That saves lives (beautifully and radically) but it comes with a long-term cost. The 3 hallmarks of a Fontan circulation are

1. Chronically elevated venous pressure (because the veins are doing the work of a missing pump),

2. Non-pulsatile low-shear blood flow through the lungs (because there’s no pump pushing blood in rhythmic bursts), and

3. Chronically reduced cardiac output (because what the single ventricle can push out is inherently limited by what passively trickles in).

Every organ in the body sits downstream of this changed circulation, and over the years, they feel it. So when we talk about a Fontan, we’re talking about a circulation under lifelong negotiation, and that distinction matters for everything that follows.

Here’s the maddening part: there is no single, universally accepted definition of Failing Fontan.

In research, “Fontan failure” has historically been defined using a formal set of clinical criteria (basically a checklist so that different hospitals studying it are talking about the same thing): NYHA functional class IV (Medical Jargon Alert: the New York Heart Association classification system, where class IV means symptoms at rest — basically unable to carry out normal daily activities without distress), or class III (symptoms with minimal activity) sustained for 12+ months without improvement; more than 2 unscheduled hospital admissions in a year for heart failure symptoms; evaluation or listing for transplant; or active protein-losing enteropathy or plastic bronchitis that hasn’t responded to treatment for 6+ months.

Those are the research definitions, and they’re useful for comparing outcomes across studies, but in your cardiologist’s office, the conversation usually starts earlier and more quietly than any of that: with trends. Pressures creeping up, saturations drifting down, exercise tolerance declining, new collaterals forming, cath lab findings showing hemodynamics that aren’t where they should be for your child’s age and time since their Fontan. The question shifts from “what is the one thing we can fix?” to “what is this circulation telling us?” — and that shift in framing is really the whole story.

For my husband and I, the picture developed through years of collateral management that slowly kept getting worse, through saturations that didn’t bounce back the way they used to, through a cath lab visit that revealed pressures her team wasn’t comfortable with. Nobody said “Aveline’s Fontan has failed”; what they said, in their careful clinical way, was that her system was under more strain than they liked, and that the management approach needed to change.

I’m happy to report that when I went digging into it, I found that the science has gotten dramatically more specific in just the last couple of years!

In 2024, Dr. Kurt Schumacher and a team of Fontan experts embarked on a groundbreaking consensus project. They used Delphi methodology (had to look it up: it’s a structured approach where experts independently assess and refine criteria until they reach a common understanding) to define and assign severity levels to the individual parts of what they’re now calling Fontan Circulatory Failure, or FCF. What they produced was essentially a map — not “failing Fontan” as a single undifferentiated bomb, but a detailed inventory of the specific domains where the Fontan circulation can cause trouble, each graded from mild to severe.

The domains span nearly every organ system. Check it out:

I’ll be honest: the first time I read through the full domain list, I needed a minute. But the point of this table-map isn’t to scare you. It’s that “failing Fontan” was never one thing; it’s always been a constellation of possibilities, and now the clinical world is finally building language specific enough to talk about them individually. So if your child’s team tells you they’re seeing signs of Fontan circulatory strain, you can ask where — hemodynamic? lymphatic? hepatic? — and that question alone transforms the conversation from existential dread into something you can actually engage with.

So I want to wade into something here, because it sits at the intersection of language, clinical culture, and the real emotional lives of CHD families.

I’ve noticed that there looks to be a philosophical debate in the Fontan world about whether “failing” is even the right word, and I think both sides have something worth hearing. On one side: the Fontan was always a palliation, not a cure, and the consequences of that altered circulation were always going to show up eventually. Some clinicians argue that calling the expected, progressive, long-term effects of a palliative circulation “failure” pathologizes something that is, in a real sense, the natural trajectory of the procedure, and it terrifies families in the process; because when we as parents hear “failing,” our brains don’t go to “a system that needs closer management” — they go to my child is dying. On the other side (and this is where I mostly sit): if we soften the language too much, we risk leaving families unprepared.

We can’t manage what we can’t name.

I’m not a fan of sanding down serious terms until they become useless little marshmallows; people deserve the truth, not a sticker chart and a vague reassurance.

But before you come at me, please let me say first that I think the answer lives somewhere in the middle (useful without being panic-inducing), and I think the field is actually getting there. The formal shift toward Fontan Circulatory Failure as a clinical term (which is what the Schumacher consensus paper and the growing body of literature now use) feels meaningful to me because it names the circulation as the thing under strain, not the child; and within that umbrella, the severity-graded domain approach gives clinicians and families language that’s specific enough to be useful without collapsing everything into a binary of fine-or-failing.

There’s also another term I want to put on your radar: Fontan management. I like personally this one because it reframes the entire conversation from a condition to a system. Your child doesn’t “have a failing Fontan” like they have a cold; your child has a Fontan circulation that requires ongoing, evolving, proactive management, and the nature and intensity of that management will change over time as the circulation changes. And while some kids might need very little intervention for decades, others will need more, sooner. But the point here is that they’re not being handed a verdict.

A mention of ”failing Fontan” doesn’t mean your child needs a transplant, nothing can be done, the original surgery was a mistake, the team has given up, or your child is ”failing.” It means the care team is seeing signs that the Fontan circulation needs more attention to all the things, and more system-thinking.

And honestly, that’s where modern Fontan care is heading anyway: away from “the Fontan is done” and toward lifelong Fontan management, with the goal of catching strain earlier, before the body has to shout.

And yeah, sometimes transplant gets discussed because a team is being responsible, not because the floor is collapsing today. I know that distinction is hard to feel in your body when you’re the parent hearing the word for the first time; your nervous system doesn’t sit back calmly and say, “Ah yes, a prudent long-term planning discussion” (in my head, it has an English accent, too — hmm, interesting). Your nervous system says, “Excuse me, what the actual hell?” And that’s fair! But the purpose of naming Fontan failure is to stop pretending the Fontan is just a surgical milestone and start treating it as a living circulation that can change, compensate, strain, and decompensate over time.

If “failing Fontan” enters your world (whether it’s in a clinic visit, a support group, or a late-night Google spiral), remember: you are allowed to slow the room down.

• You can ask what exactly the team is seeing in your child, and whether the concern is about pressures, oxygen, heart function, rhythm, collaterals, liver, lymphatics, or something else.

• You can ask what has changed compared with the previous baseline, and what the team is hoping to accomplish with whatever medication or intervention they’re recommending (and what would tell everyone it’s working).

• You can ask what would trigger an escalation in care.

• You can ask whether the conversation is about Fontan management or transplant planning or both, and what you should be watching for at home.

That doesn’t mean you’re being difficult — you are merely asking for a term to be unpacked before it takes over the room… and your central nervous system.

I don’t think we need to ban the phrase “failing Fontan.” The term exists because the problem exists, and calling it something softer won’t make high venous pressures gentler, or PLE less serious, or chronic congestion magically polite. But what I would ask for is that the clinical world stop dropping the phrase into families’ lives like a grenade with no instructions. Conversely, that also doesn’t mean to stop saying it altogether in a misguided attempt to “protect'“ us parents and going back to gatekeeping vital information. Because “failing Fontan” is not the end of the conversation but rather the beginning of a much more useful one: what part of the system is under strain, what can still be supported, what are we watching, what are we trying to prevent, and what does good Fontan management look like for this child (mine, yours), this anatomy, this body, this moment?

That’s where I think the fear will start to loosen its grip a little. Not because the situation is suddenly easy, and not because the word is less serious, but because the monster has edges now. And once something has edges, you can start turning it over in your hands; you can ask better questions, understand what your child’s care team is seeing, and tell the difference between a warning light and a verdict.

For Fontan families, that distinction is not small.

It’s oxygen.

Take heart,

— Marie-Jo 💕

• Schumacher KR, Cedars A, Allen K, et al. “Achieving Consensus: Severity-Graded Definitions of Fontan-Associated Complications to Characterize Fontan Circulatory Failure.” Journal of Cardiac Failure, Vol. 30, No. 12 (2024). — The landmark Delphi consensus paper that defined and severity-graded individual FCF domains. This is the backbone of the “what exactly is under strain?” section, and worth bookmarking if you want to understand how the clinical world is building better language for this.

• Gaebert P, Schaeffer T, Palm J, et al. “Incidence, pathophysiology, and treatment of failing Fontan after the total cavopulmonary connection.” Interactive CardioVascular and Thoracic Surgery (2024). — A large cohort study breaking down specific causes of Fontan failure in TCPC patients. Useful for understanding what kinds of problems show up and how often.

• Rychik J, Atz AM, Celermajer DS, et al. “Evaluation and management of the child and adult with Fontan circulation: A scientific statement from the American Heart Association.” Circulation, 140(6), e234–e284 (2019). — The AHA’s comprehensive scientific statement on Fontan management. If you want one document that covers the full scope of what Fontan teams monitor and why, this is it.

• Dennis M, Zannino D, du Plessis K, et al. “The Fontan Circulation: From Ideal to Failing Hemodynamics and Drug Therapies for Optimization.” Canadian Journal of Cardiology (2022). — Focuses on how Fontan hemodynamics change over time and the rational basis for medication management. The title alone captures the spectrum.

• Meza JM, Bravo-Jaimes K. “Management of circulatory failure after Fontan surgery.” Frontiers in Pediatrics (2022). — Good overview of the hemodynamic framework and drug therapies being explored. If your child is on medications to support their Fontan circulation, this gives context for what those medications are trying to do.

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