Medtronic Inc. (NYSE:MDT) issued an urgent update regarding its SynchroMed II implantable drug infusion pumps, warning that defective batteries in some of the devices might result in sudden failure.

The pumps are used primarily to treat chronic pain or severe spinal or cerebral spasticity. The issue was first reported in July 2009, and the action was labeled class II by the FDA as a problem that might cause temporary health problems or a slight threat of a serious nature.

As of May 32, 2011, there have been 55 confirmed cases of the devices failing and all but one related to pumps with batteries manufactured prior to March 17, 2005, the Fridley, Minn.-based company reported. There are nearly 140,000 pumps in use worldwide.

The problem appears to be the formation of a filmy substance within the pump battery that can lead the device to shut down suddenly, causing a patient’s pain and symptoms to return or triggering withdrawal symptoms. Returned product analysis proved the failed devices’ alarms functioned as designed, according to the company’s release.

Medtronic does not plan on recalling the SynchroMed II pumps at this time and does not recommend surgical removal unless the device manifests poor battery performance, according to company officials.