HVAD™ Performance Tracker
Background
The HVAD™ System delay or failure to restart FCA was originally communicated to clinicians in December 2020 after Medtronic identified a subset of impeller lots with a higher potential to experience a delay or failure to restart once the pump had stopped.
In that a stopped HVAD™ pump may not always successfully restart with a standard (algorithm A) controller, Medtronic developed an HVAD™ controller with modified software (algorithm B) that could be used to attempt to restart a stopped pump. This controller with modified software was only available in geographies where regulatory authorization to distribute was granted or where such authorization was not required. Based on clinical use of the algorithm B controller, an HVAD™ controller with updated software (algorithm C), comprised of algorithms A and B, was developed. The algorithm C controller received regulatory approval in May 2025 from the FDA and July 2025 from BSI. Medtronic continues to apply for regional regulatory approvals worldwide.
Differences in the controller algorithms
Controller functionality and user interface is the same for all three controllers (algorithms A, B, and C). The primary difference between them is the way in which voltage is applied to encourage the impeller to spin.
Standard controller (algorithm A controller):
- Voltage ramped up until impeller movement is detected, or maximum voltage (13 volts) is reached
- Lower rotational force (torque) to move the impeller
Repeats up to 30 times if startup unsuccessful
With the standard algorithm A controller, voltage to the impeller is ramped up until impeller movement is detected or the maximum 13 volts is reached, allowing for a lower rotational force to be used to move the impeller if possible. This cycle is repeated up to 30 times if a pump restart is unsuccessful.
Controller with modified software (algorithm B controller):
- Maximum voltage (13 volts) applied immediately to encourage the impeller to spin
- Higher rotational force (torque) to move the impeller
Repeats up to 30 times if startup unsuccessful
With the modified algorithm B controller, the maximum voltage (13 volts) is applied immediately to encourage the impeller to spin, using a higher rotational force initially. Again, this cycle repeats up to 30 times if a pump restart is unsuccessful.
Controller with updated software (algorithm C controller):
- Start attempt #1 ➔ algorithm A
⬇ if startup unsuccessful
- Start attempt #2 ➔ algorithm A
⬇ if startup unsuccessful
- Start attempt #3 ➔ algorithm B
Repeats up to 28 times on algorithm B if startup unsuccessful
The updated algorithm C controller will initially attempt to restart a stopped pump by gradually increasing voltage to the pump’s impeller using algorithm A. If the pump does not restart after two attempts using algorithm A, the software will then attempt to restart the pump using algorithm B, which immediately applies the maximum amount of voltage to start the impeller. This latter approach will continue to be used for the remaining 28 restart attempts before stopping.
Additionally, the updated algorithm C software mitigates the controller from inadvertently resetting when using a single battery to attempt a pump restart. This controller reset issue, which can occur with either algorithm A or B controllers, was discussed in the April 2024 Urgent Medical Device Communication under “Patient power source management recommendations.”
Visual attributes of the algorithm C controller
There are blue line highlights on the algorithm C controller exterior to differentiate it from previous versions, including a single blue line outlining the display screen and double blue lines around the face of the controller. On the bottom of the controller, a double blue line outlines the label and a new model number is listed (MCS1421CN). The controller’s packaging also has double blue lines outlining the label.
| Controller version | Controller face |
Controller bottom label |
Current controllers (REF: 1420) |
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Controller with updated software (REF: MCS1421CN) |
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Updated patient management recommendations when using the algorithm C controller
The HVAD™ System delay or failure to restart issue does not cause a running pump to stop; rather, the pump may fail to restart after a pump stop event. Hence, Medtronic continues to recommend reinforcing directions within the Patient Manual and Instructions for Use Medtronic manual library to patients and staff to prevent unnecessary pump stops:
- Do not disconnect the driveline from the controller
- Always ensure two power sources are connected to the controller
- Never disconnect both power sources (batteries and AC or DC adapter) from the controller at the same time; one external power source should remain connected to the controller at all times
- Do not exchange the controller unless explicitly directed by a high priority alarm condition or a VAD team member
- Reinforce the proper response to a [Controller Fault] alarm and [Electrical Fault] alarm. These are medium priority alarms unrelated to an immediate pump stop. These alarms will result in the word [Call] in the controller display, notifying the patient to call their clinician.
The recommendations about when to exchange a controller have not changed with the introduction of the algorithm C controller. Medtronic continues to recommend that considerations should be made on an individual case-by-case basis by the clinicians when deciding whether or not to electively perform a controller exchange. A controller exchange will stop the pump which can result in a pump delay or failure to restart. The algorithm C controller may not be successful in restarting all pumps.
Recommendations regarding the use of power cycling (i.e., disconnecting and reconnecting all power sources) have been updated for the algorithm C controller. Power cycling is no longer recommended after five failed start attempts with the algorithm C controller. Performing a power cycle resets the start-up algorithm to the first two attempts using gradually increasing voltage (algorithm A) instead of continuing with the maximum voltage (algorithm B).
Until algorithm C controller replacements are available at a patient’s hospital, the patient’s clinicians should continue to reference the patient management recommendations in the April 2024 Urgent Medical Device Communication.
Resources
For additional information regarding the algorithm C controller and current patient management recommendations, please reference the following links:
August 2025 Urgent Medical Device Communication for clinicians which highlights the current HVAD™ patient management recommendations in appendix B.
April 2024 Urgent Medical Device Communication under “Patient power source management recommendations”
The HeartWare HVAD™ System Instructions for Use and Patient Manual are available at Medtronic manual library