Four patients who received the HeartMate II left ventricular assist system pocket system controller have died and five more patients have either lost consciousness or experienced other problems, Thoratec announced in a safety advisory.

Thoratec issued a letter to hospitals on March 4 that described difficulties patients and caregivers had with changing from a primary system controller to a backup system controller. The company warned that eight of the nine reported events involved patients who had been trained on the EPC System Controller who then converted to the newer pocket controller. It said there were no reports of device failures.

The Pleasanton, Calif.-based company advised physicians who prescribe the device to review the updated labeling and training materials in the letter. Patients should contact their physicians to receive retraining and updated information.

The pocket controllers have been available in Europe since August 2012, and in the U.S. and Canada since May 2013. They are prescribed either at the time of the implantation of the HeartMate II left ventricular assist device, or as a replacement for an older system controller model. Thoratec identified patients who received a pocket controller as a replacement for an older model as less likely to be adequately trained and therefore at higher risk of having problems in the controller exchange process.

Thoratec and the FDA urged hospitals, physicians and patients to contact the company if they have questions and to report any adverse events to the FDA’s MedWatch Adverse Event Reporting program.