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Fontan Patients: What Residents Need to Know

Learning Objectives

By the end of this rotation, you should be able to:

  1. Understand basic Fontan physiology - why these patients are different
  2. Recognize warning signs of Fontan complications
  3. Know when to call cardiology urgently
  4. Provide appropriate supportive care when these patients are hospitalized

What Is a Fontan?

The Fontan procedure is performed for patients born with a single functioning ventricle (e.g., hypoplastic left heart syndrome, tricuspid atresia).

Simple concept: Since there's only one ventricle, surgeons redirect systemic venous return directly to the pulmonary arteries, bypassing the heart. The single ventricle pumps to the body only.

Result: Passive blood flow to the lungs (no pump) - this is what causes all the problems.

Why Fontan Patients Are Different

Feature Why It Matters for You
Low cardiac output They don't tolerate volume loss or dehydration
Elevated venous pressure Causes liver congestion, ascites, edema
Passive pulmonary blood flow Small changes in PVR dramatically affect output
Chronic hypoxia SpO2 of 85-95% may be their normal
Arrhythmia prone Atrial arrhythmias can cause rapid decompensation

Warning Signs - Call Cardiology

Urgent (Call Immediately)

Finding Concern
New arrhythmia (especially atrial flutter/fib) Can cause rapid decompensation
Significant hypoxia (SpO2 <80% or dropping) Fenestration issue, thrombus, or decompensation
Acute abdominal distension Worsening Fontan failure, PLE
Altered mental status Low cardiac output, stroke
Hematemesis or bloody stool Varices from portal hypertension

Non-Urgent but Important

  • Increasing edema or weight gain
  • Decreasing exercise tolerance
  • Protein-losing enteropathy symptoms (diarrhea, low albumin)
  • New oxygen requirement

Common Complications (Know They Exist)

Complication What It Is
Arrhythmias Atrial flutter common, can be life-threatening
Thrombosis High risk - many are on anticoagulation
Protein-losing enteropathy (PLE) Lose albumin through gut, very sick patients
Fontan-associated liver disease (FALD) Liver congestion → fibrosis → cirrhosis
Plastic bronchitis Lymphatic casts in airways - rare but serious

When These Patients Are Hospitalized

Do's

  • Call cardiology early - even for seemingly minor issues
  • Check their baseline SpO2 - many run 85-92% normally
  • Be cautious with fluids - they don't tolerate overload
  • Know their anticoagulation - many are on warfarin or aspirin
  • Get weights daily - fluid status is critical

Don'ts

  • Don't assume normal vitals - their baseline is different
  • Don't give excessive IV fluids - can precipitate failure
  • Don't delay calling cardiology for arrhythmias
  • Don't stop their anticoagulation without cardiology input

Key Teaching Points for Residents

  1. Fontan patients are fragile - what seems minor can escalate quickly
  2. Their baseline SpO2 is lower - ask or check old records
  3. Arrhythmias are emergencies - call cardiology immediately
  4. They don't tolerate dehydration OR overload - careful fluid management
  5. Many are anticoagulated - check before procedures
  6. Liver disease is universal - be aware of medications cleared hepatically

Key Guidelines

2019 AHA Scientific Statement: Evaluation and Management of the Child and Adult With Fontan Circulation Circulation. 2019;140(6):e88-e102 PMID: 31193643

Board Pearls

Pearl: Fontan patients have passive pulmonary blood flow - small changes cause big problems

Dehydration, fever, or increased PVR can dramatically reduce cardiac output. Fluid management is critical.

Pearl: Atrial arrhythmias in Fontan = emergency

Loss of atrial kick in a single ventricle circuit causes rapid decompensation. Call cardiology immediately.

Pearl: All Fontan patients develop liver disease (FALD) - it's a matter of when, not if

Be cautious with hepatotoxic medications and check synthetic function before procedures.

Self-Assessment

Question 1

A Fontan patient presents to the ED with new-onset atrial flutter. How urgent is this?

Answer **URGENT - call cardiology immediately** Atrial arrhythmias in Fontan patients are emergencies. Loss of atrial kick in a single ventricle circuit causes rapid hemodynamic decompensation. These patients do not tolerate arrhythmias well and need immediate cardiology involvement.

Question 2

What is the expected baseline oxygen saturation for a Fontan patient?

Answer **85-95%** (often 85-92%) Fontan patients have passive pulmonary blood flow and may have residual right-to-left shunting. Their "normal" is lower than typical. Always check their baseline from prior records before treating for hypoxia.

Question 3

A hospitalized Fontan patient is tachycardic with low urine output. The team orders a 20 mL/kg fluid bolus. Is this appropriate?

Answer **No - be very cautious with IV fluids in Fontan patients** Fontan physiology does not tolerate volume overload OR dehydration. A large fluid bolus can precipitate heart failure due to already elevated venous pressures. Small, careful fluid management is essential. Consult cardiology for guidance on volume status.