Atrial Fibrillation - EKG Reference Caliper Time Interval: ___ seconds Key Features RhythmIrregular RateVery fast (> 350 bpm) for Atrial, but ventricular rate may be slow, normal or fast P WaveAbsent - erratic waves are present PR IntervalAbsent QRSNormal but may be widened if there are conduction delays Notes Atrial Fibrillation EKG Reference Atrial Fibrillation Lesson Welcome to our atrial fibrillation reference page. This page provides a definition followed by an synopsis of EKG features. Links to our practice drills, quizzes, lessons and interactive guides can be found below. Definition of Atrial Fibrillation Atrial fibrillation is an irregular heartbeat which is frequently rapid. It occurs when the atria (upper heart chambers) beats chaotically. This atrial beating is out of sync with the ventricles (lower chambers of the heart). Symptoms of atrial fibrillation can include shortness of breath, exercise intolerance, heart palpitations and weakness. These symptoms may persist or reoccur. Atrial Fibrillation Electrophysiology Atrial Fibrillation occurs when multiple electrical impulses occur within within the atria. This chaotic electrical activity results in a chaotic wave form between the QRS complexes. P waves are absent. They are replaced by lower case "f" waves. No P waves means there is no PR interval measurement. This rapid electrical activity overwhelms the AV node causing impulses to enter the ventricular conduction system at irregular points. This results in irregular R to R intervals. Quick Links Sinus Atrial Junctional Ventricular Atrioventricular Pacemaker All