Key result
Oximetric Fick underestimates pulmonary blood flow ~29% and overestimates PVRI vs CMR in pre-Fontan patients.
Why the study?
Pulmonary blood flow measured by oximetry and Fick's principle is unreliable with multifocal pulmonary blood supply, commonly occurring in single ventricle patients with a BCPC and aortopulmonary collaterals.
Does the oximetric Fick method accurately estimate pulmonary blood flow and PVRI compared to CMR in pre-Fontan patients?
Observational (n=95)
Does the oximetric Fick method accurately estimate pulmonary blood flow and PVRI compared to CMR in pre-Fontan patients?
Answers are grounded in this paper and cite their sources.
In pre-Fontan patients, the oximetric Fick method underestimates pulmonary blood flow and overestimates PVRI compared to CMR, suggesting CMR should be considered for accurate risk stratification in those with high Fick-based PVRI.
Abstract Background Pulmonary blood flow (Qp) measured by oximetry and Fick's principle (FP) is unreliable if there is multifocal pulmonary blood supply with differing oxygen contents. This often occurs in single ventricle patients with a bidirectional cavopulmonary connection (BCPC) and aortopulmonary collaterals (APC). We aimed to compare the difference between cardiac magnetic resonance (CMR) measured and Fick-estimated Qp (Fick-Qp) and pulmonary vascular resistance (PVRI) at pre-Fontan assessment. Methods A retrospective analysis of BCPC patients who underwent combined CMR and catheterization under the same general anesthetic. CMR flows were measured in the superior vena cava (CMR-Qsvc), pulmonary veins (CMR-Qpv) and the difference between these was APC flow (Qapc). Oximetric Fick-Qp was compared to CMR-Qsvc and CMR-Qpv. Results Ninety-five patients were included, median (IQR): age 2.92 (2.32 - 3.38) years and weight 12.8 (11.95 - 14.65) kg. The rank order of flows was CMR-Qpv > Fick-Qp > CMR-Qsvc, median values (IQR): 3.37 (2.97 - 3.98) > 2.39 (2.09 - 2.83) > 1.91 (1.67 - 2.25) L/min/m². Hence PVRI derived from these flows were in the reverse rank order, PVRI-CMR-Qpv < PVRI-Fick-Qp <PVRI-CMR-Qsvc, mean values (95%CI): 1.37 (1.04 - 1.67) < 1.8 (1.49 - 2.18) < 2.38 (1.81 - 2.84). Conclusions In comparison to the reference method of CMR-Qpv, the oximetric Fick method underestimates pulmonary blood flow and overestimates PVRI. In patients with high Fick based PVRI, a reassessment using CMR based measurement of pulmonary blood flow should be considered for more accurate measurement of PVRI and risk stratification.
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Langanecha et al. (2026) conducted an observational in Single ventricle patients with a bidirectional cavopulmonary connection (BCPC) at pre-Fontan assessment (n=95). Oximetric Fick's principle vs. Cardiac magnetic resonance (CMR) was evaluated on Pulmonary blood flow (Qp). Oximetric Fick's principle underestimated pulmonary blood flow and overestimated PVRI compared to cardiac magnetic resonance in pre-Fontan patients.
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