What is an Atrial Rhythm on EKG?
An atrial rhythm on EKG refers to any cardiac rhythm originating from the atria rather than the sinus node, characterized by distinct P wave patterns that differ from normal sinus rhythm and include atrial tachycardia, atrial flutter, and atrial fibrillation.
Key Atrial Rhythm Categories
Atrial Fibrillation
- Characterized by replacement of consistent P waves with rapid oscillations or fibrillatory waves that vary in amplitude, shape, and timing 1
- Associated with an irregular, frequently rapid ventricular response when AV conduction is intact 1
- The ventricular response is completely irregular with no discernible P waves 1
- Represents uncoordinated atrial activation with deterioration of atrial mechanical function 1
Atrial Flutter
- Displays a saw-tooth pattern of regular atrial activation called flutter (ƒ) waves, particularly visible in leads II, III, aVF, and V1 1
- Atrial rate typically ranges from 240 to 320 beats per minute 1
- No isoelectric baseline between atrial deflections, distinguishing it from atrial tachycardia 1
- Commonly occurs with 2:1 AV block, resulting in ventricular rate of 120-160 bpm (most characteristically about 150 bpm) 1
- ƒ waves are typically inverted in leads II, III, and aVF and upright in lead V1 1
Focal Atrial Tachycardia
- Features discrete P waves with clearly defined isoelectric baseline between P waves in all leads 1
- Rate typically 130-240 beats per minute, though can range from 100 to 300 bpm 1
- P wave morphology depends on focus location and can help localize the origin before electrophysiological study 1
- Originates from a small area (focus) from where activation spreads centrifugally to both atria 1
- Common locations include the crista terminalis and pulmonary veins 1
Important Clinical Distinctions
Differentiating Features
- Atrial fibrillation: Irregular ventricular response, no P waves, fibrillatory waves 1
- Atrial flutter: Regular atrial rate, saw-tooth pattern, no isoelectric baseline 1
- Atrial tachycardia: Discrete P waves, isoelectric baseline present 1
Common Pitfalls
- AF may be misdiagnosed as atrial flutter when atrial activity is prominent on ECG in more than one lead 1
- At rapid rates with intra-atrial conduction disturbances, focal atrial tachycardia can present with an atrial flutter pattern (no isoelectric baseline) despite focal mechanism 1
- Extremely rapid rates (over 200 bpm) suggest presence of an accessory pathway or ventricular tachycardia rather than typical atrial rhythms 1
Ventricular Response Considerations
- The ventricular response depends on AV node electrophysiological properties, vagal and sympathetic tone, presence of accessory pathways, and drug effects 1
- Regular R-R intervals are possible in presence of AV block or ventricular/AV junctional tachycardia 1
- In patients with pacemakers, diagnosis may require temporary pacemaker inhibition to expose atrial activity 1