INITIAL SINGLE-CENTER EXPERIENCE WITH AN ADVANCED 3RD-GENERATION INVESTIGATIONAL DEFIBRILLATOR

The CPI PRxII is a recently approved, multitiered implantable cardiove rter defibrillator (ICD) that delivers high and low energy biphasic sh ocks, antitachycardia (ATP) and bradycardia pacing, and stores 2.5 min utes of electrograms from the widely spaced shocking electrodes. The P RxII uas implanted in 58 patients at Yale-New Haven Hospital between D ecember 1993 and January 1995. At implant, mean biphasic defibrillatio n threshold (DFT) in patients with testing to failure was 10 J (1-20). All 36 patients who were candidates for a new transvenous system unde rwent successful nonthoracotomy implantation. Based on noninvasive pre discharge EPS results, 30 patients had greater than or equal to 1 VT z one: 21 patients had ATP, 9 others had first shock less than or equal to 5 J. During follow-up, 13 patients had been treated for 379 events (range, 1-127). Of 340 events in a zone with ATP, 97% responded to ATP , 3% required shock. First programmed shock converted all events in a VF zone. Details, including RR intervals, were available for all event s in 15 of 17 patients receiving appropriate or inappropriate therapy or diverted shocks. One hundred eleven of 148 available electrograms c onfirmed VT by morphology rate, and/or presence of AV dissociation. In nine patients, electrogram data altered therapy through diagnosis of inappropriate or diverted therapy, guidance of defection enhancements, or diagnosis of previously unrecognized VTs. We conclude the PRxII ac hieves low DFTs that obviate the need for thoractomy and effectively t reats ventricular arrhythmias with ATP and shock, with programming gui ded by noninvasive electrophysiology. Multiple stored electrograms fro m widely spaced shocking electrodes greatly enhance diagnostic capabil ities, facilitating effective treatment.