Federal health regulators in the U.S. are warning the public that certain cardiac defibrillators recalled by Philips Healthcare may fail to deliver a needed shock in an emergency.

Defibrillators are used by emergency responders and others to restore normal heart function in people suffering a heart attack.

Philips Healthcare HeartStart Home Defibrillator

The FDA says an electrical problem with recalled Philips' HeartStart devices could cause them to fail to deliver a life-saving shock. (Philips Medical Systems/Associated Press)

The FDA says an electrical problem with recalled Philips' HeartStart devices could cause them to fail to deliver a life-saving shock.

Philips recalled three models of its HeartStart devices in September 2012 due to an internal electrical malfunction that could result in the device incorrectly indicating it is ready to use. The recall affects about 700,000 defibrillators sold between 2005 and 2012.

Now the company has provided more information about the recalled HeartStart FRx and HS1 (OnSite and Home) devices. The defibrillators have an electrical part called a resistor that could fail when high voltage is applied, and that could prevent the device from delivering the necessary shock. If the resistor fails, the device will emit an audible triple-chirp alert.

In Canada, Philips recalled the FRX and HS1 AED device in March and sent information letters to affected customers. The manufacturer also sent letters.

"Calling Philips for technical support at 1-800-567-1080 if the device has ever emitted or begins to emit a pattern of triple chirps is the only way to be certain that the AED will be ready for use in an emergency," a spokeswoman for Philips Canada said in an email to CBC News.

 

Until a replacement is received, the U.S. agency does recommend keeping the recalled defibrillators in service because it considers the benefits of attempting to use the device in a cardiac arrest emergency greater than the risk of not attempting to use the defibrillator, said Steve Silverman, director of the Office of Compliance in the FDA's Center for Devices and Radiological Health, in a statement Tuesday.

In March the FDA proposed new requirements for companies that manufacture external defibrillators, which are found everywhere from hospitals to schools to airports. The proposed rules would require an FDA review of devices before their launch and are intended to curb years of recalls caused by design and manufacturing flaws.

Philips said it has not received any reports of patient harm due to this recall and has been working closely with regulatory authorities and with customers to address this issue.