Pump in Parallel—Mechanical Assistance of Partial Cavopulmonary Circulation Using a Conventional Ventricular Assist Device

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Mechanical assistance of systemic single ventricle is effective in pulling blood through a cavopulmonary circuit. In patients with superior cavopulmonary connection, this strategy can lead to arterial desaturation secondary to increased inferior caval flow. We hypothesized that overall augmentation in cardiac output with mechanical assistance compensates for the drop in oxygen saturation thereby maintaining tissue oxygen delivery (DO2). Bidirectional Glenn (BDG) was established in seven swine (25 kg) after a common atrium had been established by balloon septostomy. Mechanical circulatory assistance of the single ventricle was achieved using an axial flow pump with ventricular inflow and aortic outflow. Cardiac output, mean pulmonary artery pressure (PAP), common atrial pressure (left atrial pressure [LAP]), arterial oxygen saturation (SaO2), partial pressure of arterial oxygen (PaO2), and DO2 were compared between assisted and nonassisted circulation. Significant augmentation of cardiac output was achieved with mechanical assistance in BDG circulation (BDG: median [interquartile range {IQR}], 0.8 [0.9–1.15] L/min versus assisted BDG: median [IQR], 1.5 [1.15–1.7] L/min; p = 0.05). Although oxygen saturations and PaO2 trended to be lower with assistance (SaO2; BDG: median [IQR], 43% [32–57%]; assisted BDG: median [IQR], 32% [24–35%]; p = 0.07) (PaO2; BDG: median [IQR], 24 [20–30] mm Hg; assisted BDG: median [IQR], 20 [17–21] mm Hg; p = 0.08), DO2 was unchanged with mechanical assistance (BDG: median [IQR], 94 [35–99] ml/min; assisted BDG: median [IQR], 79 [63–85] ml/min; p = 0.81). No significant change in the LAP or PAP was observed. In the setting of superior cavopulmonary connection/single ventricle, the systemic ventricular assistance with a ventricular assist device (VAD) leads to increase in cardiac output. Arterial oxygen saturations however may be lower with mechanical assistance, without any change in DO2.

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