Depression, Depressionen

Does VNS Affect Cardiac Function?

lt is logical to carefully evaluate potential cardiac and gastrointestinal effects of vagusnerve stimulation. Cardiac evaluations have been performed on more than 250 epilepsy patients in clinical trials while receiving VNS. Holter monitoring results from clinical studies in epilepsy indicated no significant changes from baseline in cardiac function during stimulation (Handforth et al 1998).

Only during the implantation procedure itself, six cases of 10‐-20-sec asystole have been reported in epilepsy patients. No cases were reported in either the epilepsy or the depression clinical trials (Rush et al 2000). All six asystoles were encountered during the diagnostics test (Lead Test) stimulation-the first stimulation that a patient receives after implantation while in the operating room. The Lead Test entails approximately 15 sec of stimulation at 1.0 mA, 500 µsec, and 20 Hz of VNS. Of these six patients, three went on to have the implant (in three others the generator and leads were removed). No long-term sequelae have been reported from any asystolic events in these patients. Most importantly, no cardiac events when the device is turned on for the first time outside the operating theater have been reported in the clinic (Asconape et al 1999; Tatum et al 1999).

What about Longer Term Efficacy and Tolerability?

In patients with epilepsy, the long-term efficacy of VNS is either maintained or improved (Morris et al 1999), and the frequency of AEs generally decreases as patients accommodate to the stimulation (Salinsky et al 1996). The patient with the longest exposure to VNS has had the System operating for 10 years (W. Duffell, Cyberonics, personal communication, October 1999).

Extensive experience in epilepsy patients provides important safety data on VNS used continuously for 1 year or longer. Side effects tend to decrease over time as patients accommodate to the effects of stimulation. Two years after initial implantation over 80% of epilepsy study patients (142/172) continued with VNS, suggesting that it is well tolerated over the long term (Cyberonics 1998).