GDT ICD 2

This page is for patients who have one of the following devices made by Guidant: Ventak Prizm AVT, Vitality AVT, Renewal AVT

The Issue: These devices can under certain circumstances have a software operating system crash and lock-up. The industry term for the phenomena seen in these devices is "functional latching". The effect of this is that these devices will suspend detection and treatment of rhythm problems in both the atria (the hearts upper chamber) and the ventricles (the lower pumping chambers). Pacing should continue in these devices but, again, no should "latching" occur, no therapy for a life threatening arrhythmia will be provided by these devices.

The Consequences: Should "latching" occur, several possible things can happen to the defibrillator. These include:

Failure to deliver therapy for atrial arrhythmias

Failure to deliver therapy for ventricular arrhythmias

Inappropriate anti-tachycardia pacing therapies in either the atria or ventricles despite the patient being in normal rhythm.

Continuous pacing at the upper rate limit of the device may be seen in a "latched" device.

Should "latching" occur, the effects on the operating system of the device by this software error are permanent and once this event occurs the only way to fix the device is to replace the device with a new defibrillator.

The Risks: This phenomena appears to be rare. Only if the device is programmed a certain way is it even susceptible to this event in the first place. If the device is programmed to make it most susceptible, the risk of "latching" occurring is 1 in 192 for every six month period. If programming of the device is made to make it least susceptible to this phenomena, the risks become very very low with chances of this happening estimated at 1 in 38,500. A software/firmware fix for this problem has been developed by Guidant and this will be available approximately in the fourth quarter of 2005. Once the device has had this new software loaded, it will no longer be susceptible to this phenomena and the risks of subsequent events of this type is thought to be zero.

Our Recommendations: All patients with these devices need to have consultations with their doctors for individualized medical advise. In general however, we suggest the following steps to take

	Interrogation of the device needs to be done by your doctor to verify normal device function
	Assuming the device is functioning normally, it should be reprogrammed to change the atrial episode data storage to 20%. Do not program atrial episode data to 0% - this can actually cause latching to occur.
	If the patient is not benefiting from anti-tachycardia pacing therapies consider programming ATP therapies to off; If these therapies are turned off, there is no risk for "latching" events to occur in this device.
	Download the firmware patch for this device from Guidant for all patients with this device once it becomes available latter this year.