Inferior Vena Cava Ultrasound Does Not Reliably Estimate Systemic Venous Pressure in Adults With a Fontan Circulation.

PURPOSE: Current ASE/EACVI echocardiography guidelines recommend estimating central venous pressure from inferior vena cava (IVC) diameter and collapsibility in biventricular circulations. Because altered blood volume, venous capacitance, and venous tone may weaken the relationship between IVC morphology and systemic venous pressure, it is uncertain whether these criteria apply in the Fontan circulation.

METHODS

In 101 adults with a Fontan circulation (median age 27.8 years), echocardiographic IVC and resting peripheral venous pressure (PVP) were measured simultaneously. ASE/EACVI guidelines were applied directly, estimating central venous pressure based on IVC diameter > 21 mm and collapsibility < 50%. Agreement with measured PVP categories was assessed using weighted κ. As a secondary post hoc analysis, IVC diameter and collapsibility thresholds were optimized within the same cohort to assess whether simple recalibration could materially improve agreement.

RESULTS

Median resting PVP was 10.6 (8.6-13.1) mmHg, and 21% had PVP ≥ 15 mmHg. IVC collapsibility was < 50% in 99%, whereas only 17% had IVC diameter > 21 mm. IVC diameter (r = 0.14, p = 0.163) and IVC collapsibility (r = -0.06, p = 0.527) did not correlate with PVP. Conventional criteria assigned no patient to the low pressure category and showed poor agreement with measured PVP (weighted κ 0.02, 95% confidence interval -0.12 to 0.16). Post hoc within-cohort recalibration (using IVC diameter ≥ 20 mm and collapsibility ≤ 10% as cut-offs) only modestly improved agreement (weighted κ 0.24, 95% confidence interval 0.05 to 0.42).

CONCLUSION

IVC-based pressure estimation is unreliable in adults with a Fontan circulation. Validated peripheral or invasive pressure measurements should be preferred for accurate Fontan pressure assessment.