INR 2.0-3.0对于非瓣膜性之心房纤维性颤动的预防是适当的


  Sept. 10, 2003—根据一篇发表于9月11日New England Journal of Medicine的群组研究结果显示,出国际标准化的比率2.0至3.0 (INR) 对于非瓣膜性之心房纤维性颤动的预防是适当的。
  
  波士顿的麻州综合医院的主要作者Elaine Hylek博士在新闻稿中表示,在进行抗凝集疗法时,造成中风的机率很低,但是这篇研究显示,可以减少经历这些异常事件的患者之严重性和并发症。
  
  抗凝集疗法和在心房纤维性颤动风险因素研究 ( ATRIA ),收集了加州13,559 位非瓣膜性之心房纤维性颤动的患者,其中596名患者在1996年到1999年之间,曾经经历局部缺血性发作,188(32%) 进行 warfarin治疗,27%接受阿斯匹林治疗,而42%在发作时未进行治疗。
  
  阿斯匹林治疗组中,严重发作或在医院死亡者占13%,而非warfarin或阿斯匹林治疗的患者占22%,接受warfarin治疗的患者占15%,而且其住院时的INR低于2.0级,5%的患者高于2.0级。对于INR低于 2.0的患者而言,严重发作的风险比率为 1.9(95% 信赖区间 [ CI ], 1.1-3.4),且30 日之内死亡的风险比率为 3.4(CI 95%, 1.1-10.1)。
  
  服用warfarin且INR高于2的患者,其发作三十日内之死亡率为6%,服用warfarin而INR低于2.0的患者,其发作三十日内之死亡率为16%,服用阿斯匹林的患者为15%,且未接受二种治疗的患者为24%。
  
  关于AF患者正确的目标INR值之辩论,包括脑部出血等出血症状增加的风险,一些近来的指导方针建议,老年发生AF的高风险患者,应该有更低的 INR,以减少出血的风险。
  
  所有抗凝集疗法都有风险存在,在不足的疗法和导致危险的可能性之间取得平衡点,是一项重要的问题。我们的结果显示,直到 INR 达到 4.0,颅内出血的风险也不会增加,因此,可以向患者和内科医生保证,目前建议的2.5 INR 目标值— 2.0 到 3.0之间的范围,是达到此一平衡点的。
  
  研究限制包括观察性的实验设计和无法强调某些只发作一次的患者并未寻找可能的医疗或成为门诊患者以接受治疗。国家老化研究所支持这项研究,DuPont Pharma提供Hylek博士和另一位研究作者的经费。
  
  Robert G.Hart博士在伴随的社论中表示,为了达到最佳的保护,抗凝集的强度必须是最适合的,许多患有非瓣膜性之心房纤维性颤动的患者,包括大部分在75 岁以下的患者,无法受益于抗凝集治疗,所以无法认同使用这种治疗取代阿斯匹林的主要防护效果。

INR 2.0-3.0 Appropriate for Pr

By Laurie Barclay, MD
Medscape Medical News

Sept. 10, 2003 — An international normalized ratio (INR) of 2.0 to 3.0 is appropriate for the prophylaxis of nonvalvular atrial fibrillation (AF), according to the results of a cohort study published in the Sept. 11 issue of the New England Journal of Medicine.

"It is very unusual to have a stroke when on anticoagulation therapy, but this study shows that it is possible to reduce the severity and complications for patients who do experience that uncommon event," lead author Elaine Hylek, MD, from Massachusetts General Hospital in Boston, says in a news release.

The AnTicoagulation and Risk Factors In Atrial fibrillation (ATRIA) study included 13,559 patients with nonvalvular AF seen at Kaiser Permanente of Northern California. Of 596 patients who experienced ischemic stroke from 1996 to 1999, 188 (32%) were receiving warfarin therapy, 27% were receiving aspirin therapy, and 42% were not receiving either therapy at the time of stroke.

Severe stroke or death in hospital occurred in 13% of patients receiving aspirin therapy, in 22% of patients receiving neither warfarin nor aspirin therapy, in 15% of those receiving warfarin therapy and with an INR level less than 2.0 on admission to the hospital, and in 5% of those with an INR level greater than 2.0. For INR less than 2.0, odds ratio for severe stroke was 1.9 (95% confidence interval [CI], 1.1 - 3.4), and hazard ratio for risk of death within 30 days was 3.4 (95% CI, 1.1 - 10.1).

Thirty-day mortality from stroke was 6% in patients receiving warfarin with INR greater than 2.0, 16% in patients receiving warfarin with INR less than 2.0, 15% in patients receiving aspirin, and 24% in patients receiving neither therapy.

Controversy about correct target INR levels for patients with AF receiving anticoagulation therapy stems from increased risk of bleeding including brain hemorrhage. Some recent guidelines have suggested that elderly, high-risk patients with AF should have lower INR targets to reduce the risk of hemorrhage.

"All anticoagulation therapy has risks, and balancing those risks against the possibility that insufficient therapy will lead to a severe stroke is a serious concern," Dr. Hylek says. "Our results show that the risk of intracranial hemorrhage does not increase until INR levels reach 4.0, which should assure patients and physicians that the currently advocated INR target of 2.5 — a range of 2.0 to 3.0 — is most likely the right balance point."

Study limitations include observational design and failure to address the possibility that some patients who had a minor stroke either did not seek medical care or were treated as outpatients.

The National Institute on Aging supported this study. DuPont Pharma, now Bristol-Myers Squibb, provided grant support to Dr. Hylek and to another study author.

"To achieve maximal protection, the intensity of anticoagulation must be optimal," writes Robert G. Hart, MD, from the University of Texas Health Science Center in San Antonio, in an accompanying editorial. "Many patients with nonvalvular AF, including most of those who are younger than 75 years of age, do not benefit sufficiently from anticoagulation to warrant its use instead of aspirin for primary prevention."

N Engl J Med. 2003;349:1015-1016, 1019-1026

Reviewed by Gary D. Vogin, MD

    



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