Haemodynamic Effect of Left Atrial and Left Ventricular Cannulation with a Rapid Speed Modulated Rotary Blood Pump During Rest and Exercise: Investigation in a Numerical Cardiorespiratory Model

PURPOSE

The left atrium and left ventricle are the primary inflow cannulation sites for heart failure patients supported by rotary blood pumps (RBPs). Haemodynamic differences exist between inflow cannulation sites and have been well characterized at rest, yet the effect during exercise with the same centrifugal RBP has not been previously well established. The purpose of this study was to investigate the hemodynamic effect of inflow cannulation site during rest and exercise with the same centrifugal RBP.

METHODS

In a numerical cardiorespiratory model, a simulated heart failure patient was supported by a HeartWare HVAD RBP in left atrial (LAC) and left ventricular cannulation (LVC). The RBP was operated at constant speed and sinusoidal co- and counter-pulse and was investigated in cardiovascular conditions of steady state rest and 80-watt bike graded exercise.

RESULTS

Cardiac output was 5.0 L min^-1 during rest and greater than 6.9 L min^-1 during exercise for all inflow cannulation sites and speed operating modes. However, during exercise, LAC demonstrated greater pressure-volume area and lower RBP flow (1.41, 1.37 and 1.37 J and 5.03, 5.12 and 5.03 L min^-1 for constant speed and co- and counter-pulse respectively) when compared to LVC (pressure-volume area: 1.30, 1.27 and 1.32 J and RBP flow: 5.56, 5.71 and 5.59 L min^-1 for constant speed and co- and counter-pulse respectively).

CONCLUSION

For a simulated heart failure patient intending to complete exercise, LVC seems to assure a better hemodynamic performance in terms of pressure-volume area unloading and increasing RBP flow.

Effects on the pulmonary hemodynamics and gas exchange with a speed modulated right ventricular assist rotary blood pump: a numerical study

Rotary blood pumps (RBPs) are the newest generation of ventricular assist devices. Although their continuous flow characteristics have been accepted widely, more and more research has focused on the pulsatile modulation of RBPs in an attempt to provide better perfusion. In this study, we investigated the effects of an axial RBP serving as the right ventricular assist device on pulmonary hemodynamics and gas exchange using a numerical method with a complete cardiovascular model along with airway mechanics and a gas exchange model. The RBP runs in both constant speed and synchronized pulsatile modes using speed modulation. Hemodynamics and airway O₂ and CO₂ partial pressures were obtained under normal physiological conditions, and right ventricle failure conditions with or without RBP. Our results showed that the pulsatile mode of the RBP could support right ventricular assist to restore most hemodynamics. Using speed modulation, both pulmonary arterial pressure and flow pulsatility were increased, while there was only very little effect on alveolar O₂ and CO₂ partial pressures. This study could provide basic insight into the influence of pulmonary hemodynamics and gas exchange with speed modulated right ventricular assist RBPs, which is concerned when designing their pulsatile control methods.

Mitral Valve Regurgitation with a Rotary Left Ventricular Assist Device: The Haemodynamic Effect of Inlet Cannulation Site and Speed Modulation

Mitral valve regurgitation (MVR) is common in patients receiving left ventricular assist device (LVAD) support, however the haemodynamic effect of MVR is not entirely clear. This study evaluated the haemodynamic effect of MVR with LVAD support and the influence of inflow cannulation site and LVAD speed modulation. Left atrial (LAC) and ventricular (LVC) cannulation was evaluated in a mock circulation loop with no, mild, moderate and severe MVR with constant speed and speed modulation (±600 RPM) modes. The use of an LVAD relieved pulmonary congestion during severe MVR, by reducing left atrial pressure from 20.5 to 10.8 (LAC) and 11.5 (LVC) mmHg. However, LAC resulted in decreased left ventricular stroke work (-0.08 J), ejection fraction (-7.9%) and higher MVR volume (+12.7 mL) and pump speed (+100 RPM) compared to LVC. This suggests that LVC, in addition to reducing MVR severity, also improves ventricular washout over LAC. LVAD speed modulation in synchrony with ventricular systole reduced MVR volume and increased ejection fraction with LAC and LVC, thus demonstrating the potential benefits of this mode, despite a reduction in cardiac output.