SynCardia Systems said today that the Class I recall of the driver for some of its total artificial heart devices was due to a single incident in which a patient briefly lost consciousness but suffered no permanent injury.

All affected devices were taken off the market 8 days after SynCardia’s initial warning August 6, the Tucson-based company said.

The FDA last week slapped the action with Class I status, denoting an issue that could result in serious injury or death. The problem involved the SynCardia device’s Freedom driver, which is attached to the heart pump and operates and monitors the device. A specific part of the Freedom Driver mechanism may fail and cause the device to stop pumping; patients with driver failures do not receive any advanced warning of the failure, only a red light and loud continuous alarm that sound after the failure.

If the part fails and the pump stops, the patient with the device will lose consciousness almost immediately, making the alarm after the failure useless. If not switched to a backup driver quickly, the patient could experience serious injury or death. A total of 29 units, manufactured between November 3, 2014 and July 29, 2015 and distributed between November 10, 2014 and July 29, 2015, are being recalled. The units are from lot number 85978, with serial numbers 85978-001 through 85978-040, and lot number 85979, with serial numbers 85979-001 through 85979-040, according to the FDA.

“The patient in the incident that prompted the recall briefly lost consciousness when his primary unit alarmed and stopped pumping, but quickly regained consciousness when his caregiver switched the patient to his backup Freedom driver. He received his replacement Freedom drivers and is doing well with no permanent injury,” SynCardia president & CEO Michael Garippa said today in prepared remarks. “No other incidents were reported.

“The malfunction was caused by an unauthorized rework of a component by a supplier. The supplier worked quickly with us to identify and resolve the problem,” Garippa said. “We want to thank the FDA for working with us in this action.”

In June, Syncardia sent a letter to surgeons  warning them about issues with a component of its artificial heart in patients who received pre-implantation circulatory rescue interventions.