HeartStart MRx Defibrillator Monitor, Model M3535A HeartStart MRx Defibrillator Monitor, Model M3536A The HeartStart MRx is for use 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 in basic life support, advanced cardiac support, or defibrillation. It must be used by or on the order of a physician

ECG signal processing chip may fail causing failure to deliver therapy in AED mode or the failure to indicate poor electrical contact (very high impedance) with the patient in Manual Defib mode.

The firm, Philips Healthcare, sent an "URGENT voluntary Medical Device Correction" Field Safety Notice, letter dated April 7, 2009, to all customers via UPS. The letter describes the product, problem and the actions to be taken by customers, with precautions to follow if the device is used before upgrade is installed. The customers were instructed to check their serial numbers for the affected product, if the device is affected, it may remain in service prior to correction using the following precautions 1) if using AED, have a back up AED; 2) if using external defibrillator paddles, disregard paddles and manually ensure good paddlet-to-patient contact, and 3) if monitoring, be prepared to switch back to the primary ECG that was initially obtained for a given patient if other leads are lost. Customers will be contacted and assisted by Philips field service engineers to install the software upgrade which corrects the problem. Should you have any questions or concerns about this Device Correction, please contact your local Philips representative at 1-800-722-9377.