search terms: lvad, vad, low flow

Background Copy Link

The LVAD controller will alarm if the flow drops below 2.5 liters/minute.  Detection of low flow varies by LVAD pump.  The provider's course of action will depend on the etiology.

Objective Copy Link

Create an algorithm for troubleshooting LVAD low flow alarms.

Potential Causes of Low Flow Alarms Copy Link

  1. Decreased preload (right heart failure, tamponade, hypovolemia, bleeding, etc.) Copy Link
  2. Obstruction of pump inflow or outflow, pump malfunction, pump thrombosis  Copy Link
  3. Systemic hypertension Copy Link
  4. Pump off event(s) or driveline disconnection Copy Link
  5. Pump thrombosis or pump malfunction Copy Link

Types of LVAD and Associated  Low Flow Detection Copy Link

HeartMate II™ flow estimation is derived from motor power and speed. Low flow alarms are uncommon as the pump tends to overestimate minimum pump flows and is challenged to see diastolic flow changes, as in the case of hypertension. HMII controller will show "---"or "+++" if it cannot accurately estimate the flow.
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HVAD™ low flow estimation is derived from power, speed, and entered HCT. Low flow alarm is set to 2.5 liters/minute; however, it can be adjusted. Copy Link

HeartMate 3™ flow estimation is derived from power, speed and entered HCT. Low flow alarms can be common as the pump is very good at estimating minimum flows (i.e. diastolic flow). Copy Link

Low Flow Algorithm Copy Link

 Special Considerations Copy Link

 HeartMate 3 System Low Flow Controller  Copy Link

  1. The HM3 System Low Flow Controller is a system controller with the low flow hazard alarm threshold set to 2 liters/minute instead of the standard 2.5 liters/minute.
  2. Physician approval is needed for a patient to be changed to a low flow system controller.  The appropriate form to be filed by an Attending Physician is referenced in this policy. 
  3. Physician approval further indicates that continued assessment and monitoring of the patient’s hemodynamic status is necessary and care will be provided accordingly.

 Risk Assessment Copy Link

  1. The requested System Controllers (Low Flow 2.0) are for use only by identified patients who would benefit from having the low flow alarm threshold lowered to 2 liters/minute. The risks of operating the HeartMate 3 LVAS at mean pump flows as low as 2 liters/minute, which is below the existing Low Flow Hazard alarm threshold of 2.5 liters/minute, are not completely understood.

References Copy Link

1. HeartMate II™ Instructions for Use Manual

2. HVAD™ Instructions for Use Manual

3. HeartMate 3™ Instructions for Use Manual