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This article was originally published in The Gray Sheet

Executive Summary

CPI VENTAK PRx ICD ONE-YEAR OVERALL SURVIVAL RATE OF 88% is found in Phase I and II multicenter trials of the third generation implantable pacemaker-cardioverter- defibrillator. Results of the trials were presented by investigator John Herre, MD, Eastern Virginia Medical School and Sentera Norfolk General Hospital, Norfolk, Virginia, at a March 16 scientific session of the American College of Cardiology's annual meeting in Anaheim, California. Herre concluded that the tiered therapy device, which provides antitachycardia pacing, low energy cardioversion and high energy shocks, is "safe in patients with ventricular tachycardia and ventricular fibrillation." The Ventak PRx studies included 372 patients who were implanted with the device at 38 centers. Males comprised 86% of the group, and the mean age of all recipients was 63.6 years. Of the total patient population, 83% had coronary artery disease underlying their ventricular arrhythmias, and 83% had monomorphic sustained ventricular tachycardia as their primary arrhythmia. At least one concomitant surgical procedure was performed in 49 patients at the time of defibrillator placement. Cardiac Pacemakers, Inc. submitted a premarket approval application for the Ventak PRx in December 1991. The device is the third generation version of the Lilly subsidiary's Ventak, which offers only defibrillation. CPI also markets a second- generation device, the Ventak P, which offers cardioversion and defibrillation. Currently, Medtronic is the only manufacturer with an approved third-generation implantable defibrillator; Medtronic gained approval for its PCD (pacer-cardioverter-defibrillator) in February ("The Gray Sheet" Feb. 15, p. 3). Behind Medtronic but ahead of CPI in the approval process is Ventritex, which was notified in December that its PMA for the Cadence V-100 pacer- cardioverter-defibrillator is approvable ("The Gray Sheet" Jan. 4, In Brief). The Ventak PRx offers up to three "detection zones"; the zones, which are programmable, are different treatment regimens provided by the device based on the patient's heart rate. If the device is programmed for more than one zone, it will progress from one zone to the next (i.e. one pacing/shock therapy routine to another), depending on whether or not an event has been successfully treated. The tiered therapy options that can be programmed in each zone include antitachycardia pacing, low energy cardioversion and high energy shock. At 12 months of followup in the study, 8,602 spontaneous episodes had been retrieved from the memories of the patients' devices. "Of the 6,916 episodes in an antitachycardia zone, 92% were terminated by antitachycardia pacing," Herre reported. The remaining 540 episodes required a secondary type of therapy by the device. When secondary therapy delivered by the device was high energy shock, it was successful in 100% of the episodes; when secondary therapy was low energy shock, it was successful in 66% of episodes. In those patients in which first and second stages of therapy were not successful, 98% of episodes were terminated with high energy shock and 2% ended spontaneously. Out of 108 patients who had episodes in a zone employing low energy cardioversion as a first-line treatment, 790 episodes or 83% were terminated with low energy shock while 99% of the remainder were terminated with high energy. In one patient, all shocks failed, resulting in death. High energy shock as an initial therapy was successful in 99% of episodes; two episodes terminated spontaneously after failure of all shocks. Efficacy of antitachycardia pacing and low energy shocks also was examined by rate of tachycardia. For rates less than 120 beats per minute, antitachycardia pacing and low energy shocks (low energy cardioversion or LEC) were "equally efficacious in approximately 93% of patients." Between 120 and 160 bpm, they also were "equally efficacious, again at 92% to 93% of episodes," Herre said. Between 161 and 200 bpm, LEC "appeared to have an advantage," and for bpm greater than 200, only 86.5% of episodes were terminated with antitachycardia pacing while 96.5% were terminated with LEC. The study showed an operative mortality of 4.5%. At 12 months, the sudden death survival rate was 98%; 95.3% of patients were free from arrhythmic death, 94.1% were free from cardiac death and the overall survival rate was 88%.



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