HeartStart MRx Defibrillator/Monitor, M3535A/M3536A Is used for the termination of ventricular tachycardia and ventricular fibrillation. The device is for use by qualified medical personnel trained in the operation of the device and qualified by training basic life support, advanced cardiac support, or defibrillation. It must be used by or on the order of a physician.

Spontaneous turn-on which could deplete the battery, rendering the device unusable until power is restored. There is also the possibility of a failure mode in which the device fails to respond to user initiated turn-on, rendering it unusable for monitoring and therapy.

Philips notified customers via Urgent Medical Device Recall Letter & Notice dated March 2009. Customers are asked to follow the "Actions to be taken by customer/user section of the Urgent Medical Device Recall Notice. In this section, customers are given the following instructions: "During the interim period, as you await the upgrade for your device, you may continue to use the Heartstart MRx. However, to reduce the risk that a spontaneous turn-on could deplete the battery, it is advised that you keep: a charged spare battery with the Heartstart MRx AC power applied, if possible, when the device is not in use You should also consider identifying a readily available backup defibrillator to use in the unlikely event that the device fails to turn on. Devices that exhibit a spontaneous turn-on or failure to respond to user initiated turn on should be removed from service as soon as possible." Philips will replace the therapy switch in affected units free of charge per Mandatory Field Change Order FC086100077. All customers will be contacted by a Philips Healthcare representative to arrange for replacement of the therapy switch in the affected devices.