Congenital heart diseaseResearch article
Accuracy of indirect Fick method for systemic flow calculation in adults with a Fontan circulation
- retrospectively studied
- clinically indicated exercise catheterization at Mayo Clinic (2018-2026)
Authors' conclusion
Empirical VO2 equations approximate resting VO2 at the cohort level, but they carry clinically relevant individual error in adults with a Fontan circulation. This error carries through to Fick-derived flow and CI classification. Direct VO2 measurement is preferable when feasible. When it is not, LaFarge & Miettinen performed best of the equations tested.
Study context
- Population
- Adults with a Fontan circulation who underwent clinically indicated exercise catheterizationadults with a Fontan circulation
- Participants
- 109 adults
- Comparison
- resting VO2 measured with a metabolic cart against the LaFarge & Miettinen, Dehmer et al., and Bergstra et al. equations
Main finding
As reported in the abstract
Measured VO2
Measured VO2
223
± 53 · mL/min
Further findings
| Outcome | Measured VO2 | LaFarge & Miettinen | Dehmer et al. | Bergstra et al. |
|---|---|---|---|---|
| Mean bias of VO2 estimates | Not reported in the abstract | mean bias −0.7 | mean bias +12.3 | mean bias +47.8 mL/min |
| Median absolute percentage errors | Not reported in the abstract | median absolute percentage error 10.1% | median absolute percentage error 11.1% | median absolute percentage error 22.1% |
| CI category misclassification | 25.7% | 27.5% | 44.0% | |
| weighted κ | Not reported in the abstract | 0.60 | 0.57 | 0.39 |
- Mean bias of VO2 estimates — 95% limits of agreement
- approximately ±33%
Correlation of measured VO2 with the estimates
- Correlation moderate
- r = 0.72-0.75
Proportional bias
- All equations showed significant proportional bias: they overestimated low VO2 and underestimated high VO2
- Higher BMI was associated with greater underestimation
Indirect Fick Qs vs direct Fick Qs
- Correlation strong
- r = 0.86-0.87
- Limits of agreement remained wide
- ∼±37%
Original publication
Accuracy of indirect Fick method for systemic flow calculation in adults with a Fontan circulation. Am Heart J. Published 11 September 2026. doi:10.1016/j.ahj.2026.107608
Summarised from the published abstract; every number is checked against it