Effect of fenestration on the sub-diaphragmatic venous hemodynamics in thetotal-cavopulmonary connection

Objective: To understand differences in the sub-diaphragmatic venous physio logy between patients with fenestrated and non-fenestrated total-cavopulmon ary connections (TCPC). Methods: We studied the effects of respiration, ret rograde flow, and gravity on the sub-diaphragmatic venous flows in 20 norma l healthy volunteers (control), 25 Fontan patients with non-fenestrated TCP C, and 21 with femestrated TCPC. Subhepatic inferior vena cava (IVC), hepat ic vein (HV), and portal vein (PV) Row rates were measured with Doppler ult rasonography during inspiration and expiration in both supine and upright p ositions. The supine inspiratory-to-expiratory flow rate ratio was calculat ed to reflect the effect of respiration, the supine-to-upright Row rare rat io was calculated to assess the effect of gravity, and the magnitude of ret rograde Row was evaluated with respect to total antegrade flow. Mean IVC, H V, and wedged hepatic Venous (WHV) pressures were measured during cardiac c atheterization in four TCPC patients before and after fenestration closure. The transhepatic venous pressure gradient (TVPG) was calculated as the dif ference between the HV and WHV pressure. Results: Compared with control, HV flow in TCPC was heavily dependent on respiration: this inspiratory capaci ty was greater in fenestrated flan non-fenestrated subjects (inspiratory-to -expiratory Row ratio 1.7, 4.4, and 3.0, respectively P < 0.001). Normal re trograde HV Row was diminished in TCPC patients, furthermore, fenestrated s ubjects had less Row reversal than non-fenestrated (retrograde as percent o f antegrade Row 43, 19, and 30%, respectively P < 0.001). Gravity decreased IVC and HV Rows more in TCPC subjects than control, but this effect was no t different between the two TCPC groups. Closure of the fenestration result ed in higher IVC and HV pressures (pre-closure versus post-closure pressure s [mmHg]: 11.2 +/- 4.0 vs. 12.3 +/- 3.9, and 11.5 +/- 3.8 vs. 12.4 +/- 3.8, respectively P less than or equal to 0.001). The normal TVPG was reduced i n fenestrated TCPC, and worsened after fenestration closure (0.9 +/- 0.3 an d 0.7 +/- 0.4, respectively P < 0.04). Conclusions: Fenestration of the inf erior venous connection has important influences on subdiaphragmatic venous return in TCPC patients. Although fenestration lowers venous pressures and partially restores TVPG, its beneficial effects on Row in TCPC patients ar e mediated primarily by an increase in inspiration-derived forward KV Row a nd reduced Row reversal. These observations suggest fenestration results in a more efficient and less congested splanchnic circulation in TCPC patient s, and may have important implications in the early and late management of Fontan patients. (C) 2001 Elsevier Science B.V. All rights reserved.