Dear Doctor:

We have recently become aware of a failure mode affecting Ventritex Cadence V-110 and V-112 series devices. It has been determined that failure of the crystal oscillator may disrupt critical timing sequences and result in erroneous values being written to the microprocessor in the device in two instances. This has caused loss of the device's serial number and resulted in inappropriate therapy parameters, specifically rapid bradycardia pacing. which may lead to the induction of potentially lethal ventricular tachyarrhythmias.

As a precautionary measure, Ventritex will issue a new programmer software release that will prevent the possibility of device pacing about 117 ppm (512 ms). This programming change is to the device hardware and is independent of the microprocessor and the crystal. This change will leave low-energy cardioversion, high-energy defibillation and bradycardia-pacing capabilities intact but, unfortunately, will eliminate the antitachycardia pacing feature of the V-110 and V-112 series devices. Additionally, non-invasive programmed stimulation and fibrillation induction will be prevented at cycle lengths less than 512 msec.

A list of your patients having V-110 and V-112 series pulse generators is provided. Since patient safety is the primary concern, this programming change will be implemented on all V-110/V-112 devices until such time as a definitive cause of these failures has been established. If the cause is identified and the scope of potentially-affected devices is narrowed, it is possible that those devices that are determined not to be affected can be programmed back to the original capabilities.

If you feel your patient requires antitachycardia pacing therapy, Ventritex will provide a replacement Cadet V-115 series device without cost to the patient. The Cade V-115 and Contour V-145 devices are of a different design, use different components, and are not subject to this potential failure mode.

Your Ventritex representative will be contacting you with further details about this programmer software revision and will assist you in any way in facilitating the scheduling and programming of your patients.

The Food and Drug Administration is aware of this situation and will monitor the progress of these activites. We sincerely apologize for this inconvenience to you and your patients but we are convinced this is the best course of action to assure patient safety.

If you have any questions, please contact your local Ventritex representative or call our office at 1-800-733-3455.

Sincerely,

Frank M. Fischer
President and Chief Executive Officer

Enclosures

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