Physiology and Clinical Utility of HeartMate Pump Parameters

Abstract

The HeartMate 3 left ventricular assist device (LVAD) is now the only centrifugal pump intended for durable support being actively manufactured and implanted for adults in the United States. The changes in preload and afterload that accompany common clinical scenarios experienced by patients with an LVAD will cause specific changes to the LVAD pump parameters, namely, the pump power, pulsatility index, and flow. Appropriate care of this unique, and growing, population requires a full understanding of these variables as well as the underlying physiologic principles governing their derivation. The aim of this review is to focus on the updated functionality of the HeartMate 3, specifically in comparison to the HeartMate II, as well as the application of pump parameter interpretation to common clinical scenarios.

Keywords: HeartMate; Left ventricular assist device; pulsatility index; pump parameters.

Fig. 1.

A – HeartMate 3, B – HeartMate II, Green arrow Rotor drive power needed to rotate the rotor and generate blood flow, Blue arrows – Pump power going down Driveline to the pump, Red arrows – System Power going into the Controller from batteries.

Fig. 2.

A – HeartMate II; B – HeartMate 3; Ovals – region of imprecise flow calculations.

Fig. 3.

Variation in pump power throughout cardiac cycle in relation to LVAD flow and aortic and left ventricular pressures.

Fig. 4.

Estimated Flow throughout Cardiac Cycle based on Power.

Fig. 5.

Variation in pump flow throughout cardiac cycle in relation to LVAD flow and aortic and left ventricular pressures.

Fig. 6.

A – LVAD operating on the flat part of the HQ curve B – LVAD operating on the steep part of the HQ curve; DeltaP flow. AoP, aortic pressure; LVP, left ventricular pressure.

Fig. 7.

A – HeartMate II HQ Curve, B - HeartMate 3 HQ Curve.

Fig. 8.

Pump flow–pulsatility vs time. PI, pulsatility index.

Fig. 9.

Normovolemia HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 10.

Hypovolemia HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 11.

Estimated Flow vs Time.

Fig. 12.

Hypervolemia HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 13.

Normotensive HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 14.

Hypertensive HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 15.

Right Ventricular Failure HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 16.

No Aortic Insufficiency HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 17.

Aortic Insufficiency HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 18.

Cardiac Tamponade HQ Curves during Inspiration and Expiration with Associated Flows throughout Cardiac Cycle.

Fig. 19.

Degree of Inflow or Outflow Obstruction and Associated Harmonic Oscillation.

Fig. 20.

Intra-aortic Balloon Pump HQ Curves during “On” and “Off” Modes with Associated Flows throughout Cardiac Cycle.

Fig. 21.

High and Low RPM HQ Curves with Associated Flows throughout Cardiac Cycle.

Fig. 22.

Cardiac Recovery HQ Curve with Associated Flows throughout Cardiac Cycle.

Fig. 23.

Summary of Differential Diagnosis Based on Pump Flow and Pulsatility.