Automated continuous rhythm monitoring with implantable cardiac monitor and real-time smartphone alerts during af episodes: SMART-ALERT study
Authors: Briosa E Gala A , Pope M T B , Leo M , Sharp A J , Varini R , Paisey J R , Curzen N , Banerjee A , Betts T R 
Published: May 2024

Abstract

Introduction
The 'Pill-in-the-pocket' oral anticoagulation (OAC) strategy is based upon the concept of dynamic thromboembolic risk which increases during and shortly after an atrial fibrillation (AF) episode. Limiting OAC use in low-risk patients with infrequent AF may offer comparable stroke protection and reduce bleeding. However, this approach relies on precise continuous rhythm monitoring with real-time alerts to patients. LINQ II implantable cardiac monitor transmits regularly to Carelink via smartphone app, but lacks patient alerts. To address this limitation, we developed bespoke software that triages transmissions in Carelink and sends alerts via SMS to patients.

Purpose
This feasibility study evaluates the precision of the LINQ II in detecting AF and assesses the efficacy of bespoke software in delivering 'real-time' SMS alerts to participants' smartphones, and measures compliance with these alerts.

Methods
In this single-center feasibility study, individuals with frequent AF episodes underwent LINQII implantation. The bespoke software, operating in the cloud, systematically reviewed all Carelink transmissions at 5-min intervals. SMS alerts were triggered based on specific criteria: 1)AF &gt;30 min; 2)only the initial AF episode &gt;30 min within a 24h period was transmitted; and 3)AF episodes uploaded or detected after a 24h delay were disregarded. Participants confirmed receipt of the alert by responding to the SMS, and timestamps for these interactions were recorded in a database (Fig. 1).

Results
A total of 50 patients were prospectively enrolled, and LINQ II was implanted. The median age was 49 years, 62% male, 90% had paroxysmal AF. Over a 3-month mean follow-up, 4080 AF episodes &gt;30 min occurred in 32 patients. Among these, 700 met the criteria for triggering an alert, with 72.14% sent to patients within 24 h. Alerts were not transmitted for 3 main reasons: smartphone failure to transmit to Carelink within a 24 h period, software issues connecting to Carelink (website maintenance), and updates in the webservers. The median time from an AF episode to the transmission of SMS alerts was 2.47 h, with 85.54% of alerts being sent within 12 hours. Once an SMS was sent, the median time for acknowledgment was 4.3 min. The median time from an AF episode to acknowledgment was 4.23 h (Fig. 2). Notably, 97.62% of episodes were acknowledged within 24 hours. Patients failed to acknowledge an SMS alert on only 3 occasions.

Conclusions
Safely delivering 'pill-in-the-pocket' OAC requires a closed-loop system where devices provide real-time alerts during during AF , thus minimising delays in initiating OAC. This feasibility study establishes that the integration of bespoke software with LINQ II exhibits promising efficacy with a high percentage of SMS alerts within 24 hours, exceptional patient compliance, and a median response time of only 4.3 min. Nonetheless, further efforts are needed for seamless integration with Carelink to enhance connectivity.