Hemodynamic effects of partial ventricular support in chronic heart failure: Results of simulation validated with in vivo data

A, Pressure-volume relationships for normal and varying degrees of heart failure conditions. LV, Left ventricular; CHF, congestive heart failure. B, Pressure and flow tracings for normal and varying degrees of heart failure. Extreme left shows tracing in normal condition, with increasing degrees of failure progressing from left to right. MVF, Mitral valve flow; AoF, aortic flow.

A, Pressure-volume loop at baseline heart failure state (solid line), with pump on (simulation 26,000 rpm, 3 L/min flow) and withdrawing blood from the left atrium (dashed line), and withdrawing blood from the left ventricle (dotted line). LVD, left ventricular dysfunction; LA, left atrium; Ao, aorta; LVAD, left ventricular assist device; LVP, left ventricular pressure; LVV, left ventricular volume. B, Pressure and flow tracings with the pump off and on (approximately 26,000 rpm, 3 L/min flow) in left atrial (LA)–aortic (Ao) and left ventricular (LV)–aortic bypass configuration. LVAD, Left ventricular assist device; MVF, Mitral valve flow; AoF, aortic flow.

A, Total cardiac output (CO) as a function of ventricular assist device flow. The difference in the slope of the relationship for mild and severe heart failure indicates that the effect of partial ventricular assist device support on cardiac output is greater when the heart is less dilated and weak. CHF, congestive heart failure; LVAD, left ventricular assist device. B, Left ventricular end-diastolic pressure (LV EDP) as a function of ventricular assist device flow, further substantiating that this model predicts any degree of partial support to be hemodynamically more effective in states of mild compared with severe heart failure. CHF, Congestive heart failure; LVAD, left ventricular assist device.

A, Effect of patient volume status on ventricular assist device performance during mild and severe heart failure. At each level of heart failure, partial ventricular assist device support increased total output by the same amount at any given intrinsic cardiac output value. CO, Cardiac output; LVAD, left ventricular assist device; CHF, congestive heart failure. B, Effect of patient volume status on left ventricular end-diastolic pressure (LV EDP) with ventricular assist device support during mild and severe heart failure. The effect of partial ventricular assist device support on LV EDP was nonlinear, having a greater effect at lower end-diastolic pressures. LVAD, Left ventricular assist device; CHF, congestive heart failure.

A, Demonstration of the effects of preload and afterload manipulation to optimize the hemodynamic effectiveness of a partial-support ventricular assist device. LVP, Left ventricular pressure; CHF, congestive heart failure; LVAD, left ventricular assist device; LVV, left ventricular volume. B, Hemodynamic parameters with varying preload and afterload with and without partial ventricular assist device support. LV EDP, Left ventricular end-diastolic pressure; MAP, mean arterial pressure; CO, cardiac output; CHF, congestive heart failure; LVAD, left ventricular assist device.

A, In vivo relationship of pump output and total cardiac output. This relationship approximates the same relationship resulting from the simulation. B, In vivo relationship between pump output and left atrial pressure (LAP). Note the similarity of the in vivo relationship to the simulated relationship.

As the severity of disease increases from normal to New York Heart Association class III and IV and ultimately to cardiogenic shock (CGS), the possible maximal cardiac output decreases from that capable of supporting full exertion to that barely necessary to support life. Partial support fills the gap between patients needing small amounts of hemodynamic support to meaningfully enhance exercise tolerance, such as can be provided by cardiac resynchronization therapy (CRT), and those with severe heart failure who require a device that fully assumes the work of the heart. LVAD, Left ventricular assist device.

Electrical analog modeling cardiovascular system.

Pressure-flow characteristics of pump modeled. The gray box demarcates clinically relevant operating points for the pump.