Table of contents
- 1. Introduction
- 2. Hemodynamics
.
Introduction
- LVADs have become popular in recent years
- Few donors, large need
- Improved short and medium-term outcomes with VADs
- LVADs can be used for:
- 1. Bridge to transplant
- 2. Destination therapy (if ineligible for transplant)
- VADs are composed of:
- 1. Blood Pump
- Inflow Cannula, Impeller, Outflow Cannula --> dacron graft --> aorta
- 2. Percutaneous Lead
- 3. External Power
- 4. System Controller
- 1. Blood Pump
Hemodynamics
- Pump differential pressure (difference between pump LV pressure and aortic pressure)
- Flow inversely correlated to differential pressure
- Similar kinetics in LVAD as heart
- Sensitive to preload and afterload
- Pulsatility is achieved by systole (ventricle contracts, pushing more blood into LV) and diastole
- Centrifugal pumps are more sensitive to pressure changes (more pulsatility)
- Pumps MORE sensitive to afterload changes than the biologic LV (3-4 times)
- Pumps are LESS sensitive to preload than biologic LV
- Preload is VERY important for heart flow.
- Afterload dose change output as well
- R-heart is extremely important to supply enough blood for VAD preload (maintain LV filling)
- During conditions of low ventricular preload, axial pumps tend to “suck” harder than centrifugal pumps, and may even lead to a self-latching condition, as the pump continues to increase suction as flows fall, resulting in suck-down of the ventricular wall around the inflow cannula. In this regard, centrifugal pumps are less likely than axial pumps to create ventricular suck-down at low flow.
- Suction Events
- Occur when not enough preload for the LV and LVAD, suction occurs of ventricular wall on the inflow cannula.
- When this happens, LVAD shifts to lower preprogrammed pump speed
- Suction events can trigger arrhythmias and need to be avoided.
- Poor preload and high flows can trigger arrhythmias. Patients with RV failure are at HIGHEST RISK.
- LVAD can improve native LV function by decreasing LV diameter, which improves passive pressure-volume relationship.
- RV function can also improve by dropping RV afterload and improving venous return.
- Can improve pulmonary hypertension, and slowly improve PVR
- Can exacerbate TR
- RAMP Study
- RAMP Study = measurement of central venous and pulmonary artery wedge pressures and cardiac output at increasing pump speeds
- Sequential increase in pump speeds to see if they can tolerate higher speeds (find optimal speed)
- To decrease risk of suction events
Comments