Normal Fontan Pressure
Normal Fontan pressure is generally considered to be less than 15 mm Hg, with pressures ≥20 mm Hg definitively classified as elevated and warranting advanced heart failure consultation 1.
Defining Normal vs. Elevated Fontan Pressure
The 2023 Circulation guidelines from ACTION provide the most authoritative framework for understanding Fontan pressures 1:
- Normal range: While many individuals with Fontan circulation have normal end-diastolic pressures during cardiac catheterization, the guidelines indicate that Fontan pressure ≥20 mm Hg represents a major hemodynamic disturbance requiring advanced heart failure consultation
- Threshold for concern: Pressures in the 15-20 mm Hg range represent a gray zone where clinical context matters
Clinical Context and Variability
There is notable variability in how clinicians define elevated Fontan pressure 2. A 2025 multinational survey of 170 congenital heart disease cardiologists revealed:
- 53% defined elevated Fontan pressure as >15 mm Hg
- 33% used >18 mm Hg as the threshold
- 14% used >20 mm Hg as the cutoff
This heterogeneity underscores the lack of standardized hemodynamic parameters, though the most recent guideline consensus clearly identifies ≥20 mm Hg as pathologically elevated 1.
Exercise Hemodynamics
During exercise, different thresholds apply 3:
- Elevated exercise mean PA pressure: >25.8 mm Hg (defined as two standard deviations above mean values in patients with normal Fontan hemodynamics)
- Normal Fontan patients during exercise typically maintain mean PA pressures around 16 mm Hg (14.5-19.5 mm Hg)
Clinical Implications
Fontan pressure ≥20 mm Hg is an independent predictor of adverse events including death and need for transplantation 1. This threshold should trigger:
- Advanced heart failure consultation
- Evaluation for anatomic stenoses amenable to catheter-based intervention
- Assessment of ventricular end-diastolic pressure (pathologic if >15 mm Hg)
- Consideration of pulmonary vasodilator therapy
- Evaluation of cardiac index (concerning if <2 L/min per m²)
Common Pitfalls
- Do not rely on IVC ultrasound to estimate Fontan pressure—it shows poor correlation with actual systemic venous pressure in this population 4
- Recognize that Fontan pressures can be transiently elevated with volume expansion even when resting pressures appear normal
- Ambulatory monitoring data suggests that individual mean PA pressure changes >4 mm Hg or absolute values >24 mm Hg may be associated with heart failure-mediated events 5