连续AF监测引出干预时机问题

圣迭戈——在美国心脏协会主办的国际卒中大会上公布的CRYSTAL-AF研究显示，美敦力公司的Reveal XT置入式心脏监测装置可检出传统方法漏检的房颤(AF)。



这项北美和欧洲研究由芝加哥西北大学心脏病科的Rod Passman医生及其同事进行，入组隐源性缺血性卒中或短暂性脑缺血发作(较为少见)的患者，221例患者被随机分入Reveal XT装置组，220例被分入使用心电图(ECG)或24-h Holter监测仪的常规标准监测组(对照组)。这些入组患者的平均年龄为62岁，大部分为男性。Reveal XT装置为电脑U盘大小，在局部麻醉下被置入左胸肌肉下，可通过无线方式传输数据。

结果显示，6个月后，该装置在19例(8.6%)患者中检出AF。标准监测在3例(1.4%)患者中检出AF[风险比(HR) 6.4；95%可信区间(CI)，1.9~21.7；P=0.0006]。Reveal XT装置组14例(74%)AF患者无症状，18例(94.7%)的治疗方案从抗血小板治疗变更至口服抗凝剂治疗。对照组1例AF患者无症状，2例改用口服抗凝剂。该研究中的每例患者既往均出现栓塞事件且之后的CHADS2评分≥2，因此均符合抗凝治疗条件，但研究开始时接受抗凝治疗的患者数量很少。

1年后，Reveal XT装置在29例(13.1%)患者中检出AF，其中大部分患者无症状。标准监测在4例(1.8%)患者中检出AF，其中2例无症状(HR 7.3；95% CI 2.6~20.8；P＜0 .0001)。对照组检出4例AF患者需121次ECG检查、32次Holter监测和1个事故记录仪。两组中几乎全部的AF患者均改用抗凝剂。

Reveal XT装置组27例(93%)AF患者出现最长持续1天的每次持续6 min以上的AF发作；13 例(45%)出现持续12~24 h的AF发作。

3年时，Reveal XT装置仍优于传统方法，在电池寿命方面 (HR 8.8；95% CI 3.5~22.2；P＜0.0001)。5例(2.3%)患者因感染或口袋侵蚀而取出Reveal XT装置。

Reveal XT和其他现代置入式装置善于检出AF，这可能并不令人惊讶，但有时不太清楚应如何处理AF。研究者未报告该研究中的AF发生频率及卒中、死亡和抗凝并发症例数。如果某人发生卒中，之后又被检出AF，则很难对这一问题视而不见。对于较年轻的患者和卒中风险低的患者，可能不必过多担心。然而，目前正在了解到抗凝剂对高危患者有效。许多研究都是在发生大量AF的患者中进行，但即使是小的AF发作也可能增加长期卒中风险，但尚不清楚阈值是什么，而且也不知道是否存在风险特别高的亚组。

该研究获美敦力公司资助。Passman医生声明因参与该研究而从美敦力公司获得酬金，并且从该公司获得大量研究资金及演讲和咨询费。另外11名研究者声明从该公司获得酬金。3名研究者为美敦力员工。

专家点评：检出持续时间长的发作有助于改善治疗

哈佛医学院的神经学教授Steven Greenberg医生表示，长期心脏监测正在开始发挥作用，并且AF过度治疗是个令人担心的问题。至于如何在风险与获益之间划界限，仍存许多问题。该研究中的许多患者出现持续12~24 h的AF发作，因此AF导致其首次卒中的可能性较高。如果最终连续监测检出的AF病例的卒中风险与我们目前发现的数量明显较少的AF病例的卒中风险一样高，则具有重要意义，因为我们有口服抗凝剂这一有效治疗。

Greenberg医生声明无相关经济利益冲突。

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By: M. ALEXANDER OTTO, Cardiology News Digital Network

SAN DIEGO – Medtronic’s Reveal XT heart monitor implant detected atrial fibrillation missed by older techniques in a randomized trial.

The company’s North American and European CRYSTAL-AF (Cryptogenic Stroke and Underlying Atrial Fibrillation) trial randomized 221 patients to the device after cryptogenic ischemic strokes or, less commonly, transient ischemic attacks, and 220 others to usual monitoring with ECGs or 24-hour Holter monitors. The Reveal XT device, about the size of a computer thumb drive, is slipped under the flesh on the left side of the chest with local anesthesia, and transmits data wirelessly.

After 6 months, the device picked up atrial fibrillation (AF) in 19 patients (8.6%). Standard monitoring detected AF in three patients, or 1.4% (hazard ratio, 6.4; 95% confidence interval, 1.9-21.7; P = .0006).
 
Fourteen (74%) Reveal XT AF patients were asymptomatic, and 18 (94.7%) were switched from antiplatelet therapy to oral anticoagulants. One control group AF patient was asymptomatic, and two were switched to oral anticoagulants. Every patient in the trial was eligible for anticoagulants because of past embolic events and subsequent CHADS2 scores of 2 or more, but few were on anticoagulants when the trial started.

It’s probably not a surprise that Reveal XT and other modern implantable devices are good at finding AF, but it’s less clear sometimes about how to handle it. The investigators did not report the frequency of AF or the number of strokes, deaths, and anticoagulation complications in the trial.

"If someone had a stroke, and then is found to have AF, it’s hard to ignore that," said presenter and investigator Dr. Rod Passman, a cardiologist and professor of medicine at Northwestern University in Chicago.

There may be less to worry about with younger patients and those with few stroke risks. The mean age in the trial was 62 years, and most of the subjects were men.

However, "we are learning that anticoagulation is effective" in high-risk patients. "The studies were done on patients with a lot of AF, but even small episodes may increase the long-term stroke risk. We are not clear about what the threshold is, but I do think we are honing in [on it]. The question will be if there’s a subgroup at a particularly high risk," he said at the International Stroke Conference, sponsored by the American Heart Association.
 
After a year, Reveal XT had detected AF in 29 patients (13.1%), most of them asymptomatic. Standard monitoring found AF in four (1.8%), two of whom were asymptomatic (HR, 7.3; 95% CI, 2.6-20.8; P less than .0001). Detecting AF in the four control arm patients took 121 ECGs, 32 Holter monitors, and one event recorder. Almost all of the AF patients in both groups were switched to anticoagulants.

About 27 (93%) of the device AF patients had a maximum 1-day AF duration of more than 6 minutes; about 13 (45%) had episodes of 12-24 hours.

The device continued to outperform older methods at 3 years, the life of its battery (HR, 8.8; 95% CI, 3.5-22.2; P less than .0001).

It was taken out of five patients (2.3%) because of infections or pocket erosions.

Dr. Passman reported payments from Medtronic to work on the trial and significant research grants and speakers’ bureau and consultant fees from the company. The other 11 investigators disclosed personal payments from the company. Three were Medtronic employees. The company funded the trial.

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Detection of lengthy episodes could improve treatment
 
Long-term cardiac monitoring is coming into play, and [overtreatment of atrial fibrillation] is a legitimate concern. There’re many questions about where to draw the line between risks and benefits.

But a lot of people in this trial had episodes lasting 12-24 hours, so the probability is high that AF caused their initial stroke. If it turns out that continual monitoring identifies AF cases with the same high stroke risk as the much smaller group we are picking up now, the implications are enormous because we have effective treatments: oral anticoagulants.

Dr. Steven Greenberg is a professor of neurology at Harvard Medical School in Boston. He said he had no relevant financial disclosures.