Bipolar leads have one positive and one negative pole.

But unlike the Accufix lead, the J-shaped wire in the Encor bipolar lead was shielded under layers of metal and, the company thought, could not work its way out if it fractured.

This technology uses a single bipolar lead to accentuate trends in brain wave activity (mostly frontal cortex), which may then be interpreted more quickly in the acute care setting, resulting in a faster clinical intervention where needed.

Dr. Brinker and others began asking whether the defect was restricted to the Accufix leads or whether another lead made by Telectronics Pacing Systems, the Encor bipolar lead, might also have a tendency to fracture.