延长植入式心律转复除颤器(ICD)识别窗口可减少不适当放电

波士顿(EGMN)——意大利IRCCS人类临床研究所的Maurizio Gasparini博士在美国心律学会年会上报告称，ADVANCE III试验结果表明，延长植入式心律转复除颤器(ICD)识别窗口可安全、有效地减少不适当抗心动过速起搏(ATP)和放电治疗。

在该项随机试验中，研究者从94个中心入组1,902例植入单腔、双腔ICD或心室再同步心脏转复除颤器(CRT-D)的患者。主要终点为周期间期≤320 ms的自发性心律失常ATP和放电治疗下降≥20%，共计891例识别间期数目(NID)设置为18/24的TAP治疗患者和876例NID为 30/40患者的临床数据可用于首要终点分析。患者以男性为主(84%)，平均年龄65岁。各组均有近半数患者为纽约心脏协会心功能分级Ⅲ和Ⅳ级心衰，60%患有冠心病，平均左心室射血分数为30%。约75%患者ICD植入目的为一级预防，40%患者植入CRT-D，31%为双腔ICD，29%为单腔ICD。

在中位随访时间为12个月的意向治疗分析中，97例NID 30/40患者经历346次治疗(ATP或放电)，而149例NID 18/24患者经历557次治疗(发生率比值为0.63，P<0 .001)。Kaplan-Meier分析表明，识别窗口较长患者的无治疗时间优势明显。晕厥和死亡事件均无显著组间差异，NID 30/40组和18/24组发生晕厥的患者比例分别为1.5%和0.8%，死亡率分别为5.1%和5.9%。

研究者此前发现，66%的室颤(VF)和91%的快速室性心动过速(FVT)在30次心动内自行终止(Eur. Heart. J. 2009;30:2758-67)，但两家主要的ICD生产商仍标称(在包装盒上)VF识别窗口设置为2~3 s，有可能导致令人不快和不必要的电击。本次试验结果表明，ICD植入患者NID设置为30/40与18/24相比，可减少室性治疗(ATP和放电)37%，且晕厥和死亡率未见显著差异，证实延长识别窗口策略可安全、有效地减少不必要的ICD治疗，从而改善患者生活质量。同时也表明，在许多情况下生产商标称的ICD设置或许过于保守。

会议主持人、布里格姆妇女医院心律失常预防中心的Christine M. Albert博士质疑上述安全性结果，认为两组晕厥发生率均过低。Gasparini博士对此表示认同，但强调在每组受试者中，约20%患者在植入前曾经历至少1次晕厥事件。虽然从理论上讲，受试者属于晕厥发生率较高的人群，但试验中并没有出现非常高的晕厥发生率。

该研究由美敦力公司资助。Gasparini博士报告无相关利益冲突，两位共同作者为美敦力公司雇员。Albert博士曾接受St. Jude医疗公司研究资助，并担任诺华制药顾问。

BOSTON (EGMN) – Tweaking implantable cardioverter defibrillator settings to lengthen the detection window is safe and significantly reduces inappropriate antitachycardia pacing and shocks, an investigator said at the annual meeting of the Heart Rhythm Society.

Patients with ICDs programmed with a number of intervals to detect (NID) of 30/40 beats had a 37% reduction in ventricular therapies (antitachycardia pacing and shocks), compared with patients with ICDs programmed with a NID of 18/24 beats, with no significant differences in syncope or deaths between the groups, reported Dr. Maurizio Gasparini of Istituto Clinico Humanitas IRCCS, Milan.

“This strategy is demonstrated to be safe and effective in reducing unnecessary ICD therapy, and increasing consequently the quality of life of these patients,” Dr. Gasparini said on behalf of coinvestigators in the randomized ADVANCE III (Avoid Delivering Therapies for Nonsustained Arrhythmias in ICD Patients III) trial.

In a previous trial, Dr. Gasparini and colleagues showed that 66% of ventricular fibrillation (VF) episodes, and 91% of fast ventricular tachycardia (FVT) episodes terminated spontaneously within 30 beats (Eur. Heart. J. 2009;30:2758-67), yet two major ICD manufacturers still have nominal (in-the-box) settings of only 2-3 seconds for a VF detection window, potentially leading to unpleasant and unnecessary shocks, he said.

The ADVANCE III investigators enrolled 1,902 patients from 94 centers with single-chamber, dual-chamber, or cardiac resynchronization therapy-defibrillator (CRT-D) ICDs. In all, 891 of those assigned to NID 18/24 programming with antitachycardia pacing (ATP) during charging and 876 patients assigned to NID 30/40 with ATP had available clinical data for the primary end point: a 20% or greater reduction in ATP and shocks for spontaneous arrhythmia with a cycle length of 320 ms or less.

The patients were predominantly male (84% in each arm) with a mean age of 65. Nearly half of patients in each group had New York Heart Association class III or IV heart failure, and 60% had coronary artery disease. The mean left ventricular ejection fraction in each group was 30%.

The devices were implanted for primary prevention in about 75% of patients in each arm. About 40% had CRT-Ds, 31% had dual-chamber devices, and 29% had single-chamber ICDs.

At a median follow-up of 12 months in an intention-to-treat analysis, 97 patients assigned to NID 30/40 had experienced 346 therapies (ATP or shock deliveries), compared with 149 patients and 557 therapies in those assigned to NID 18/24 (incidence rate ratio [IRR] 0.63, P less than .001), meeting the primary end point.

A Kaplan-Meier analysis also showed that the longer detection window was significantly better at keeping patients therapy free over 12 months.

There were no significant differences in syncopal events, which occurred in 1.5% of patients in the 30/40 group, compared with 0.8% in the 18/24 group, or in deaths, which occurred in 5.1% of patients randomized to the 30/40 strategy, and 5.9% of those assigned to 18/24.

The results suggest that “in many cases the nominal ICD settings are probably too conservative,” Dr. Gasparini said.

Session comoderator Dr. Christine M. Albert, director of the center for arrhythmia prevention at Brigham and Women’s Hospital in Boston, challenged the safety findings, noting that the incidence of syncope in both treatment arms was extremely low.

Dr. Gasparini agreed, but noted that in each arm of the study population, about 20% of participants had experienced one or more syncopal episodes prior to device implantation.

“This was a population that theoretically may have a high incidence of syncope; nonetheless, we did not observe very high incidence of it,” he said.

The study was supported by Medtronic. Dr. Gasparini reported having no conflicts of interest. Two of the study coauthors are Medtronic employees. Dr. Albert has previously received research support from St. Jude Medical and was a consultant to Novartis.