A modified LVAD technique to augment caval and pulmonary arterial blood flow in the 'failing Fontan' circulation

Background There are minimal circulatory support options for patients with a failing Fontan. The Heartmate II (HMII) left ventricular assist device (Thoratec, Bedford, MA) in its packaged state cannot augment caval/pulmonary arterial blood flow. Aim We hypothesized that a modified HMII pump could augment caval and pulmonary arterial blood flow. Methods A bifurcated ringed Gore-Tex graft (W. L. Gore & Associates, Flagstaff, AZ) was sewn to the HMII inflow, and the outflow graft transected and tapered from 16 mm to 8 mm in diameter. In three sheep, the inflow and outflow grafts were anastomosed end-to-side to both cava and the pulmonary artery. Results Following baseline measurements, the pump speed was increased to 8000 revolutions per minute (RPMs). Compared to baseline, at 8000 RPMs, there were no significant differences in mean arterial, central venous, or pulmonary arterial pressure. However, there was a significant decrease in right ventricular diastolic diameter (3.1 ± 0.1 vs. 1.8 ± 0.2 cm, R = 0.6, p = 0.02) and similarly a decrease in pulmonary arterial pulse pressure (8.5 ± 2.1 vs. 2.1 ± 2.9 mmHg, p = 0.01). As pump speed increased, there was a corresponding increase in pump flow and power, with a decrease in pulsatility index. Conclusions These findings suggest that the HMII may be modified to provide caval/pulmonary circulatory support for the failing Fontan circulation.