Mechanical Support of the Failing Heart

First Things First

• Indications for mechanical support: NYHA class IV heart failure secondary to ischemic or non-ischemic cardiomyopathy (viral, peripartum, alcoholic, infiltrative)
• What is accomplished by providing mechanical support? Offloads the failed ventricle, allows time for recovery, supports end organs
• What options are available? Pulsatile and non-pulsatile (axial flow) devices exist, and best individual fit is determined by a combination of size, durability, and etiology of heart failure.
• Which physiologic parameters are controlled by the device?
  • Pump output = pump rate x pump stroke volume
    • Pump rate may be adjusted by changing pump frequency (pulsatile) or revolutions per minute (axial flow).
    • Stroke volume (or equivalent) may be adjusted by adding vacuum to pulsatile devices or adjusting afterload for axial flow devices.
  • CO = HR x SV
• Which physiologic parameters can be controlled medically or pharmacologically? Preload, pulmonary vascular resistance, native heart rhythm, systemic vascular resistance, native heart contractility