Summary of findings and strength of evidence.

Background and aim
Implantable cardiac monitors (ICM) can facilitate the detection of asymptomatic atrial fibrillation episodes. We performed a systematic review and meta-analysis to investigate whether ICM can prevent stroke in patients with prior stroke and risk factors for stroke.
Methods
This study included randomized controlled trials comparing ICM with conventional (non-ICM) external cardiac monitoring in patients with prior stroke and risk factors for stroke. We searched Medline, Embase, and CENTRAL from inception until January 5, 2022, without language restriction. Quantitative pooling of the data was undertaken using a random-effects model. The primary outcome was ischemic stroke at the longest follow-up.
Results
Four trials comprising 7237 patients were included. ICM was significantly associated with decreased risk of ischemic stroke (RR 0.76; 95% CI, 0.59–0.97; moderate-quality evidence) in patients with prior stroke and risk factors for stroke. ICM was associated with higher detection of atrial fibrillation (RR 4.21, 95% CI 2.26–7.85) and use of oral anticoagulants (RR 2.29, 95% CI 2.07–2.55).
Conclusions
ICM results in a significantly lower risk of ischemic stroke than conventional (non-ICM) external cardiac monitoring in patients with prior stroke and risk factors for stroke. Due to the clinical heterogeneity of study population and limited related studies, more trials were needed to furtherly explore the topic in patients with prior stroke or high risk of stroke.

研究背景与目的
植入式心脏监测器（Implantable Cardiac Monitor, ICM）可辅助检出无症状性心房颤动发作。本研究开展系统综述与荟萃分析，旨在探究植入式心脏监测器能否预防既往有卒中病史且存在卒中危险因素患者的卒中事件。

方法
本研究纳入对比植入式心脏监测器与常规（非植入式心脏监测器）体外心脏监测在既往有卒中病史且存在卒中危险因素患者中应用效果的随机对照试验。我们检索了Medline、Embase及CENTRAL数据库，检索时限从建库至2022年1月5日，未对语言进行限制。采用随机效应模型对数据进行定量合并分析。主要结局指标为最长随访周期内的缺血性卒中事件。

结果
共纳入4项随机对照试验，涉及7237例患者。在既往有卒中病史且存在卒中危险因素的患者中，植入式心脏监测器与缺血性卒中风险显著降低相关（相对风险RR=0.76；95%置信区间CI：0.59~0.97，证据质量为中等）。植入式心脏监测器可提高心房颤动检出率（RR=4.21，95%CI：2.26~7.85）及口服抗凝药物使用率（RR=2.29，95%CI：2.07~2.55）。

结论
相较于常规（非植入式心脏监测器）体外心脏监测，植入式心脏监测可显著降低既往有卒中病史且存在卒中危险因素患者的缺血性卒中风险。由于研究人群存在临床异质性且相关研究数量有限，未来需开展更多试验以进一步探究该主题在既往有卒中病史或卒中高风险人群中的应用价值。