久しぶりの投稿である。NEJMに「iWatchと不整脈モニター」の論文報告が載った。このテーマは従前より知られていたこと（すなわちアップルがiWatchを販促するのにデモしていたいわば『売り』であった）だから、とても興味があったわけだ。
かつてiPhoneが売りに出されて重心動揺計が内蔵された頃、スタンフォード大学がパーキンソン症候群の患者さんにiPhoneをつけてもらい、出たばかりの新薬（歩行動揺を抑える作用がある薬）の治験を開始したことがあった。たった一日で５万人？の治験参加者を得ることができたというニュースに驚愕したことがあった。米国でも治験参加者を５万人集めるには数十箇所の医療センターが協力して１年はかかる（日本では未来永劫、こんな数字絶対無理！！）と言われていた大規模治験があっというまにできたことと、患者からは治験センターに「毎日リアルデータ」が患者の知らないうちに送られてくるという斬新なシステムに驚いたことがあった。あれから10年くらいたつかな。
今回の不整脈とはもちろん心房細動（af）でありエンドポイントは脳梗塞の発症予防なのだ。これは素晴らしいプロジェクトだと思う。高齢者増えると心房細動は急増する。ということは脳梗塞も急増する。脳梗塞は治療可能である。しかしADLは確実にさがる。確実に下がったADLを持つ患者が長生きする時代である。政府や世間が騒ぐ「健康寿命」を大きく損なうのが脳梗塞であり、その大きな原因の一つがafである。だいたいほとんどの人は自分にafがあるなんて知らない。ほとんどの脳梗塞はいきなり襲ってくるはずなのだ。
予防しかない。一歩譲って予測しかない。
Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation
November 14, 2019
N Engl J Med 2019; 381:1909-1917
Abstract
BACKGROUND
Optical sensors on wearable devices can detect irregular pulses. The ability of a smartwatch application (app) to identify atrial fibrillation during typical use is unknown.
METHODS
Participants without atrial fibrillation (as reported by the participants themselves) used a smartphone (Apple iPhone) app to consent to monitoring. If a smartwatch-based irregular pulse notification algorithm identified possible atrial fibrillation, a telemedicine visit was initiated and an electrocardiography (ECG) patch was mailed to the participant, to be worn for up to 7 days. Surveys were administered 90 days after notification of the irregular pulse and at the end of the study. The main objectives were to estimate the proportion of notified participants with atrial fibrillation shown on an ECG patch and the positive predictive value of irregular pulse intervals with a targeted confidence interval width of 0.10.
RESULTS
We recruited 419,297 participants over 8 months. Over a median of 117 days of monitoring, 2161 participants (0.52%) received notifications of irregular pulse. Among the 450 participants who returned ECG patches containing data that could be analyzed — which had been applied, on average, 13 days after notification — atrial fibrillation was present in 34% (97.5% confidence interval [CI], 29 to 39) overall and in 35% (97.5% CI, 27 to 43) of participants 65 years of age or older. Among participants who were notified of an irregular pulse, the positive predictive value was 0.84 (95% CI, 0.76 to 0.92) for observing atrial fibrillation on the ECG simultaneously with a subsequent irregular pulse notification and 0.71 (97.5% CI, 0.69 to 0.74) for observing atrial fibrillation on the ECG simultaneously with a subsequent irregular tachogram. Of 1376 notified participants who returned a 90-day survey, 57% contacted health care providers outside the study. There were no reports of serious app-related adverse events.
CONCLUSIONS
The probability of receiving an irregular pulse notification was low. Among participants who received notification of an irregular pulse, 34% had atrial fibrillation on subsequent ECG patch readings and 84% of notifications were concordant with atrial fibrillation. This siteless (no on-site visits were required for the participants), pragmatic study design provides a foundation for large-scale pragmatic studies in which outcomes or adherence can be reliably assessed with user-owned devices. (Funded by Apple; Apple Heart Study ClinicalTrials.gov number, NCT03335800.)
