Advanced electrocardiography (A-ECG) technology achieved excellent reproducibility when estimating heart age from standard 12-lead ECGs in 42 healthy young adults. Within single sessions, the AI-driven heart age measurements showed 99% reliability (ICC 0.99) with just 5.8% variation between readings. Between sessions conducted 14 days apart, reproducibility remained good at 84% reliability, though heart age estimates increased slightly from 24.0 to 25.5 years on average. This technology calculates a "heart age gap" by comparing estimated cardiovascular age to chronological age, potentially offering a new tool for communicating cardiovascular risk to patients in accessible terms. The findings suggest A-ECG could reliably track cardiovascular aging over time, though this preprint study awaits peer review and results may change. The research addresses a critical gap in cardiovascular assessment by validating measurement consistency, essential for any clinical tool. However, the study's limitation to healthy young adults means reproducibility in older populations or those with cardiovascular disease remains unestablished. While promising for risk communication, the clinical utility and prognostic value of heart age gaps require validation in larger, more diverse populations before widespread clinical adoption.