Criteria for Atrial Fibrillation
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Article at a Glance
- Atrial fibrillation is characterized by:
- Regularity: Very irregular
- Rate: Atrial rate > 350 bpm but difficult to measure; ventricular rate < 100 bpm
- P Wave: Unable to discern
- PR Interval: Not measurable
- QRS Complex: < 0.12 second
We interpret several criteria on the patient’s ECG tracing to determine atrial fibrillation (AF). When determining AF, you’ll first notice a lack of a P wave. During atrial fibrillation, the atrial chambers are firing from multiple foci. The firing is quick, random, and chaotic, frequently occurring at a rate of 300–350 bpm with no discernible P-wave on an ECG tracing. There are no P waves present during atrial fibrillation because the atria are firing rapidly and chaotically. As the random, rapid firing conductions hit the AV node, it lets some through but holds others back. As it conducts down through the ventricular chambers and produces a QRS, the R-R interval will always be irregular with no discernible pattern. Read: Criteria for a SVT (supraventricular tachycardia) There will be no pattern to the R wave. If the ventricular rate is less than 100 bpm, it’s a controlled atrial fibrillation. If the ventricular rate is greater than 100 bpm, it’s an uncontrolled atrial fibrillation or atrial fibrillation with rapid ventricular response (RVR).Criteria to Determine Atrial Fibrillation
Related Video – ECG and the Cardiac Cycle Basics
Related Video – ECG Rhythm Review – Atrial Fibrillation with Rapid Ventricular Response (RVR)
Summary
We look for two criteria on the ECG tracing during atrial fibrillation. The patient will not have a P wave, and the R-R intervals are narrow and irregular, with no discernible pattern.
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