ICD的效果建立在血管再造的時間點上


  May 11, 2005 (紐奧良) - 在心律研究協會(HRS)的第26屆年會上有一項發表,根據第二次的多中心植入式自動去顫器臨床試驗(MADIT-II)結果顯示,對於曾經接受冠狀動脈血管再造手術的患者,植入式心臟整流去顫器(ICD)若在血管再造術完成六個月以後植入,效果會更好。
  
  研究人員表示,根據之前的隨機分配試驗結果,篩選過的心臟病高危險患者,ICD的使用可以降低死亡率達30%到45%;但是,冠狀動脈繞道手術臨床試驗計畫(CABG)則指出,若在血管再造手術時植入ICD作為預防,患者的存活率並不會有改善的現象。
  
  HRS的上任會長Stephen C. Hammill醫師表示,初期的CABG-Patch試驗,追蹤期不夠長;本項研究有著足夠的追蹤期以看出正面的效果,但是,也獲知疾病仍然會繼續進展的事實。
  
  研究人員在作報告時指出,在這項次屬研究裡,相較於傳統治療組,患者在血管再造手術6個月以後才接受ICD的植入,所有因素的死亡率會降低36%,因突發性心臟病死亡的機率也會降低66%;但若ICD在手術後6個月內即已植入,則無法看出任何效益。
  
  在原來的MADIT-II試驗裡,研究人員對1232位心肌梗塞及心臟射出分率低於30%的患者進行ICD的療效評估,這些患者在參與試驗前,症狀皆持續最少一個月以上;以隨機性的方式將患者分配至ICD與傳統治療合併組,或傳統法單一治療組;整體的研究結果顯示,ICD的治療,關係著31%的死亡率降低量。
  
  在現行的分析中,研究人員針對血管再造手術的時間點,與ICD治療效益之間的關係作評估;951位患者的血管再造術,是在參與試驗前6個月左右進行的;這些患者中,有130位的血管再造手術是在試驗前6個月之內進行的。
  
  根據多變因分析,ICD若是在血管再造手術後6個月以內植入,無助於存活率的改善;紐約羅徹斯特大學醫學中心的Ilan Goldenberg醫師向Medcape表示,兩組皆有著相似的死亡率(約10%)。
  
  根據交叉性的個案分析結果,對於傳統治療組,在血管再造術完成6個月以後,死亡率有著急劇的增加;突發性心臟病的死亡率則高出6倍。
  
  Goldenberg醫師指出,血管再造手術後3至6個月內接受ICD的患者,並不會獲致任何的正面效益;但若植入的時機是在6個月以後,ICD的效果會隨著植入時機的延後而越趨明顯。
  
  若ICD植入的時間點超過6個月,死亡率會隨著時程而顯現層次性的降低(7至12個月,13至24個月,25至72個月,及超過72個月)。
  
  Goldenberg向Medscape表示,血管再造手術在初期,似乎可以預防患者因突發性心臟病而死亡;患者若在手術後3到6個月內即接受植入,無法獲得任何效果;但是血管再造的效果會在6個月以後開始降低,取而代之的是,ICD開始提供正面的效益。
  
  最後,Goldenberg醫師指出,是否在冠狀動脈血管再造6個月以後使用ICD,必須根據患者的個人狀況作評估;若患者為缺血性心臟病,心臟射出分率低於30%,亦可適用ICD而無副作用,就可以在6個月以後作ICD的植入。
  
  該研究報告的作者中有三位為Guidant Corporation Scientific Study/Trial的成員。

Efficacy of ICD Based on Timin

By
Medscape Medical News

Linda Little

May 11, 2005 (New Orleans) — The efficacy of an implantable cardioverter defibrillator (ICD) in patients who have previously undergone coronary revascularization is more efficacious if the device is implanted six months after revascularization, according to a substudy of the second Multicenter Automatic Implantable Defibrillator Trial (MADIT-II) presented here at the 26th annual scientific sessions of the Heart Rhythm Society.

ICDs can reduce mortality by 30% to 54% in appropriately selected high-risk cardiac patients according to previous randomized trials, the researchers said. However, the Coronary Artery Bypass Graft (CABG)-Patch Trial showed no improved survival in patients with prophylactic ICDs implanted at the time of elective revascularization.

"The initial trial (CABG-Patch) didn't have a long enough follow-up," said Stephen C. Hammill, MD, immediate past president of the Heart Rhythm Society. "This study had enough follow-up to see the benefits occur, but the disease will still continue to progress."

In the substudy, patients receiving an ICD six months after revascularization had a 36% reduction in all-cause mortality and a 66% reduction in sudden cardiac death compared with the conventionally treated group, the researchers reported. But patients who received an ICD within six months of revascularization had no benefit.

In the original MADIT-II trial, researchers evaluated the efficacy of ICD therapy in 1,232 patients who had a myocardial infarction and an ejection fraction of 30% or lower at least one month prior to enrollment. Coronary revascularization procedures were performed in 951 patients who were then randomly assigned in a 3:2 ratio to receive either an ICD or conventional therapy. The overall results of the study indicated that ICD therapy was associated with a 31% reduction in mortality.

In the current analysis of the trial, MADIT-II investigators compared outcomes of ICD patients who had undergone revascularization less than vs more than 6 months before device implantation. Of the 1,232 patients, 62 patients received an ICD within six months of revascularization; 520 patients received an ICD more than six months after revascularization; and the remaining patients received conventional therapy.

According to a multivariate analysis, there was no survival benefit to ICD therapy in patients who received the ICD within six months of revascularization in both the ICD and the conventional groups, with about a 10% mortality rate, lead investigator Ilan Goldenberg, MD, told meeting attendees. Dr. Goldenberg is a cardiologist at the University of Rochester Medical Center in New York.

In a case-crossover analysis, the mortality rate for the conventionally treated group dramatically increased six months after revascularization; the rate of sudden cardiac death in these patients increased sixfold.

"Patients who received an ICD three to six months after revascularization didn't get any benefit of the implant," Dr. Goldenberg said. "But after six months there was an increasing trend in each time period towards ICD effectiveness."

This reduction in mortality was consistent across every time period after six months (7 to 12 months, 13 to 24 months, 25 to 72 months, and more than 72 months).

Dr. Goldenberg told Medscape it appears that the revascularization procedure initially tends to protect patients from sudden cardiac death. "Patients who received an ICD three to six months after revascularization didn't get the benefit of the implant," he said. "But the effect of revascularization begins to reduce after six months and the ICD becomes beneficial."

ICD use beyond six months after coronary revascularization should be considered on an individual basis, said Dr.Goldenberg. "If a patient has medical indications for ICD with ischemic heart disease and an ejection fraction below 30% with no other contraindications, then...wait six months, then implant an ICD."

Three of the authors are members of the Guidant Corporation Scientific Study/Trial. The remaining authors, including Dr. Goldenberg, have no commercial relationships to disclose.

HRS 26th Annual Scientific Sessions: Abstract 17. Presented May 5, 2005.

Reviewed by Gary D. Vogin, MD

Linda Little is a freelance writer for Medscape.

    
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