Overview
This lecture covers the main types of atrial rhythms, focusing on how to identify premature atrial complexes (PACs), atrial flutter, atrial fibrillation (AFib), and supraventricular tachycardia (SVT) on ECG, along with their key features and treatments.
Premature Atrial Complexes (PACs)
- PACs are early, abnormal atrial impulses causing premature P waves on ECG.
- The premature P wave may look different or be hidden in the preceding T wave.
- A pause may follow the QRS, or the QRS may be dropped or abnormally wide.
- Treatment is usually unnecessary, but frequent PACs may indicate risk for more serious arrhythmias.
Atrial Flutter
- Atrial flutter is identified by saw-tooth "flutter" (F) waves instead of P waves.
- Ventricular rhythm is regular; F waves are regularly spaced.
- Atrial rate is extremely fast, typically 250–400 beats per minute.
- QRS complexes are usually normal (<0.12 seconds).
- Treatments include cardioversion and antiarrhythmics.
Atrial Fibrillation (AFib)
- AFib lacks clear P waves, showing irregular "fib" waves between QRS complexes.
- Ventricular rhythm is irregular; atrial rhythm is also irregular and very fast (350–600 bpm).
- QRS complexes remain normal in duration.
- Treatments include cardioversion, antiarrhythmics, and anticoagulation to prevent clot formation.
Supraventricular Tachycardia (SVT)
- SVT is any abnormally fast rhythm originating above the ventricles, usually in the atria.
- Includes sinus tachycardia, AFib, and atrial flutter.
- Ventricular rhythm is regular; P waves are often not visible due to rapid rate.
- Heart rate is over 100 bpm, commonly 150–250 bpm.
- QRS complexes are narrow (<0.12 seconds).
- Treated with cardioversion or antiarrhythmics.
Key Terms & Definitions
- P wave — the ECG representation of atrial depolarization.
- Premature Atrial Complex (PAC) — an early, abnormal atrial beat.
- Atrial Flutter — arrhythmia with saw-tooth flutter (F) waves on ECG.
- Atrial Fibrillation (AFib) — arrhythmia with chaotic, irregular fib waves and no P waves.
- Supraventricular Tachycardia (SVT) — any rapid rhythm originating above the ventricles.
Action Items / Next Steps
- Review ECG examples of each atrial rhythm type.
- Prepare to learn details of antiarrhythmic drugs and cardioversion in future lectures.