Venous Pressure Cost for Cardiac Index Increases During Exercise in Patients with Fontan Circulation Versus Those with Biventricular Circulation.

Patients with Fontan circulation (Fontan) have a higher venous pressure (VP) and lower cardiac index (CI) than those with biventricular circulation (BiV). Although the cost to increase VP per unit CI (ΔVP/ΔCI) during exercise is expected to be higher in Fontan than in BiV, to our knowledge, no previous study has specifically tested ΔVP/ΔCI as the main variable.We included 9 patients with Fontan and 10 with postoperative BiV in this pilot study and assessed their hemodynamics via an ergometer-based exercise test. CI was continuously measured using impedance cardiography.The median age and quartile range values in patients with Fontan (15.0 [13.6, 16.7] years) were significantly higher than those in patients with BiV (12.9 [11.3, 14.3] years, P = 0.028). The ΔVP/ΔCI values were significantly higher in the Fontan group than in the BiV group at 25 W (4.5 [4.3, 6.0] versus 1.1 [0.9, 2.6] mmHg/ (L/minute/m2), respectively; P = 0.0008) and peak exercise (3.6 [33, 4.5] versus 1.1 [0.9, 1.5] mmHg/ (L/minute/m2), respectively; P = 0.0002) irrespective of age. The areas under the curve values of the 2 receiver operating curves (at 25 W and peak exercise time points) were 0.961 and 0.967, respectively. Patients with Fontan exhibited the 3 highest ΔVP/ΔCI values at peak exercise had an elevated New York Heart Association functional class (IIm-III) and hemodynamic concerns.Patients with Fontan displayed a higher cost to increase VP per unit CI. ΔVP/ΔCI may be a potential circulatory or prognostic marker for these patients and its value should be validated via larger prospective studies.