Atrial Cardiomyopathy and Ischemic Stroke: A Monitoring-Integrated Staging and Phenotyping Framework Beyond Atrial Fibrillation

In many patients with cryptogenic stroke or embolic stroke of undetermined source (ESUS), the atrium remains clinically relevant even when atrial fibrillation (AF) is not detected with routine or extended cardiac monitoring. The construct of atrial cardiomyopathy (AtCM) addresses this problem by characterizing a measurable atrial substrate rather than relying solely on a binary search for AF. Thus, this narrative review proposes a framework that integrates cardiac monitoring with a staging system to describe AtCM following ischemic stroke. Moreover, this review distinguishes arrhythmogenic AtCM, which primarily facilitates AF detection, from thrombogenic AtCM, an emerging concept that reflects blood stasis, left atrial appendage dysfunction, endocardial–endothelial activation, and coagulation activation. Recent neutral or mixed anticoagulation trials suggest that broad atrial stress markers are insufficient for selecting patients for empiric anticoagulation. Therefore, we present a Stage 0–4 classification system that links phenotype burden to monitoring intensity and research eligibility. This framework is intended to standardize reporting, guide the intensity of monitoring, support upstream risk-factor management, and improve trial enrichment. However, this framework is not intended to replace guideline-based decisions regarding antithrombotic therapy.