Cardiac HealthStream Telemetry Practice Exam 2026 - Free Telemetry Practice Questions and Study Guide

When a sinus rhythm includes premature atrial contractions, you’ll see an early P wave that looks different from the normal sinus P waves, followed by an early, but usually narrow, QRS complex. This premature beat interrupts the regular rhythm, and then the rhythm resumes with the next normal sinus beat. The ventricular conduction is typically normal, so the QRS duration stays narrow. The presence of an abnormal premature P wave ahead of an early QRS, with a return to the regular sinus pattern afterward, is the telltale sign of PACs. If you only saw absent P waves, a prolonged QT, or inverted T waves, those would point to other issues, not PACs within sinus rhythm.