Accurate coding of recorded ECGs is critical for patient care. The ECG Coding Reference Guide provides a standard language for ECG interpretation. In addition, it offers medical professionals a quick, easily accessible, and comprehensive guide of the ECG findings that led to the ECG’s final interpretation code. Sinus rhythm • Default rhythm of the heart, whereby pacemaking impulses arise from the sinus (sinoatrial, SA) node and are transmitted to the ventricles via the AV node and His-Purkinje system • P normal axis (0° to +75°, upright in I and II +/- aVF and V4-V6, inverted in aVR) and same morphology • Atrial rate (adults): 60-100 beats/min (age-specific heart newborn 110-150 beats/min, 2 years 85-125 beats/min, 4 years 75-115 beats/min, 6+ years 60-100 beats/min)