Despite standardization efforts, cardiac implantable electronic devices (CIED) report atrial fibrillation (AF) episodes differently across device manufacturers. Similarly, traditional cardiac rhythm management (CRM) protocols have failed to standardize physician-indicated AF. Thus, few studies have characterized the frequency and accuracy of device-indicated AF. This study quantified and compared physician- (‘true’ AF incidence) and device-indicated AF across two patient segments and by CIED manufacturer. Baptist Health Network in Kentucky uses a CRM care platform (Murj, Santa Cruz, CA) to manage 12,000 patients across 14 clinics. Both device- and physician- indicated AF transmissions in 10,986 CIED patients (age 76+12 yrs) including pacemakers, ICD, CRT-P, CRT-D implants between 10/1/2020-5/31/2022 were assessed. AF transmissions were also analyzed in 3,290 (30% of 10,986 pts) pacer dependent or heart block (HB) patients (defined as AV block or had a non-CRT device with average RV pacing >90%) (age 80+11 yrs). True physician-indicated AF episodes represented 31% & 33% of all pts & HB transmissions corresponding with 72% & 68% all pacing/HB pts. Device-indicated AF represented 32% & 33% all pacing/HB transmissions. Overall, 19% & 20% all pacing/HB transmissions were true positives (TP=device- & physician-indicated AF). Device percentages by manufacturer were 35% Boston Scientific, 29% St. Jude, 27% Medtronic, and 8% Biotronik. Medtronic had the lowest device-indicated AF transmissions/pt, the highest true positive rate at 75% (TPR=true positives / total device-indicated AF transmissions) & highest false negative rate at 30% (FNR=false negatives/ total device-indicated normal transmissions). Biotronik had the highest false positive rate at 50% (FPR= false positives/ total device-indicated AF transmissions) & lowest false negative rate (FNR) at 14%. The mean TPR was 61%+11% per manufacturer. The Murj CRM system allows greater standardization of device- and physician-indicated AF episodes, enabling quantification of device-indication frequency and accuracy. In this study, physician-indicated AF was common (72% all pacing patients; 68% HB patients) with often inaccurate AF device classifications. Alternating high FPR and FNR by manufacturers highlight the optimization challenge of reducing false alarms while maintaining a high TPR. Studies like this provide critical context for clinicians interpreting device-indicated events across manufacturers required by CRM.