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Dr. Alessandro Giardini
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This calculator estimates the post-Fontan central venous pressure (CVP-TCPC) from pre-operative Glenn haemodynamic data and quantifies the associated risk of early Fontan failure (EFF), based on the cohort study by Quail, et al published in the Journal of Thoracic and Cardiovascular Surgery.
The calculation uses a two-step formula derived from the published paper. First, the pulmonary vascular resistance is estimated from the Glenn catheter data by dividing the central venous pressure at the BCPC stage by the indexed SVC flow. The estimated CVP-TCPC is then obtained by multiplying this resistance estimate by the anticipated total indexed cardiac output after the Fontan completion.
PVR estimated = CVP at BCPC divided by Q-SVC
CVP-TCPC = PVR estimated multiplied by Q-TCPC
The threshold of clinical significance identified in the Quail et al. cohort is a CVP-TCPC of 33 mmHg or above. Patients meeting or exceeding this threshold had a significantly higher risk of early Fontan failure and a median five-day longer hospital stay on multivariable median regression, after adjustment for venous collateral grade.
The calculator requires three numerical inputs and one anatomical selection.
The CVP in BCPC or Glenn is the mean central venous pressure measured at the pre-operative cardiac catheterisation during the Glenn stage, expressed in millimetres of mercury.
The indexed SVC flow (Q-SVC) is the indexed superior vena caval cardiac output measured at the same catheterisation, expressed in litres per minute per square metre.
The estimated total indexed TCPC flow (Q-TCPC) is the anticipated post-Fontan indexed cardiac output, typically estimated from the full inferior plus superior vena caval return, expressed in litres per minute per square metre.
The SVC anatomy field selects between single SVC and bilateral SVC, as the published odds ratios for early Fontan failure differ between these anatomical groups. The association was statistically significant only in the single SVC group.
The calculator displays the estimated CVP-TCPC in millimetres of mercury alongside the intermediate PVR estimate. A risk classification indicates whether the value meets or exceeds the 33 mmHg high-risk threshold. The published odds ratio for early Fontan failure per millimetre of mercury increment in CVP-TCPC is shown for the selected anatomy, together with the approximate 95% confidence interval and p value from the paper. An approximate absolute EFF risk is also displayed, derived from the baseline cohort prevalence of seven events in 131 patients. A hospital stay association summary reflects the multivariable median regression finding from the paper.
This calculator implements a formula from a single-centre retrospective cohort study of 131 patients with seven early Fontan failure events. Wide confidence intervals are expected given the small number of events and should be interpreted accordingly.
The estimated CVP-TCPC overestimates directly measured intensive care unit CVP by approximately seven millimetres of mercury on average. The two measures are not interchangeable.
The bilateral SVC odds ratio did not reach statistical significance in the published cohort, and the CVP measurement at BCPC stage may be technically less reliable in patients with bilateral SVCs due to asymmetric SVC size and inter-Glenn pulmonary artery narrowing.
This tool estimates research-derived risk association and is intended to support multidisciplinary discussion and clinical decision-making. It does not replace cardiac catheterisation data, formal haemodynamic assessment, or the judgement of the clinical team.
Quail MA, Chan I, Sarna S, Hughes M, Muthurangu V. A Preoperative Estimate of Central Venous Pressure Is Associated with Early Fontan Failure. Journal of Thoracic and Cardiovascular Surgery (accepted manuscript). Single-centre retrospective cohort, Great Ormond Street Hospital, n=131.
Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist
Written: 02/07/2026
Last reviewed: 02/07/2026