During October 2024, imkn enhanced ECG data modeling in the jami-fhir-jp-wg/jp-core-v1x repository by standardizing the representation of electrocardiogram data within JP Core FHIR. They developed new value sets and code systems for ECG categories, durations, and stress types, and introduced aliases to support consistent classification and interpretation of ECG observations. Using FSH and YAML, imkn focused on FHIR Implementation Guide development and terminology management to improve interoperability and analytics readiness. The work emphasized explicit, reviewable changes and robust version control, resulting in higher data quality and more consistent ECG data interpretation across JP Core FHIR deployments.