Atrial Premature Beats (APBs) on ECG

Introduction

Atrial premature beats (APBs), also called premature atrial contractions (PACs), are early heartbeats originating from the atria. They are common and usually benign but can be associated with underlying heart disease or arrhythmias.

ECG Characteristics of APBs

1. Early P wave: The premature P wave appears earlier than expected in the normal rhythm cycle.
2. Abnormal P wave morphology: The shape of the P wave is different from the sinus P wave because the electrical impulse originates from an ectopic atrial focus.
3. Narrow QRS complex: Since the impulse propagates normally through the AV node and His-Purkinje system, the QRS complex remains narrow (<120 ms) unless a bundle branch block is present.
4. Compensatory pause: After the APB, a slight pause is often observed before the sinus rhythm resumes.
5. Non-conducted APB: Sometimes, an APB occurs so early that it finds the AV node refractory, leading to a missing QRS complex.

Clinical Significance

• Benign in most cases: Often discovered incidentally on an ECG or Holter monitor.
• Possible symptoms: Palpitations, skipped beats, or mild discomfort.
• Risk factors: Stress, caffeine, alcohol, smoking, and electrolyte imbalances.
• Association with arrhythmias: Frequent APBs (>5% of total beats) may predict atrial fibrillation.

Management

• Lifestyle changes: Avoid caffeine, alcohol, and stress.
• Electrolyte balance: Maintain good hydration and potassium levels.
• Medication: Beta-blockers or antiarrhythmic drugs in symptomatic patients.
• Further evaluation: If APBs are frequent, an echocardiogram or Holter monitor may be warranted.

Conclusion

APBs are usually benign but can hint at underlying heart conditions. Recognizing their ECG features helps in proper diagnosis and risk stratification.

Source recommendations

1. American Heart Association Guidelines for Arrhythmia Management

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
2. https://www.heart.org/en/health-topics/arrhythmia
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
4. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/tachycardia--fast-heart-rate
5. https://pubmed.ncbi.nlm.nih.gov/16949478/

2. European Society of Cardiology Guidelines on Atrial Fibrillation

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Atrial-Fibrillation
2. https://academic.oup.com/eurheartj/article/42/5/373/5899003
3. https://www.escardio.org/static-file/Escardio/Guidelines/Documents/ehaa612.pdf
4. https://academic.oup.com/eurheartj/article/45/36/3314/7738779
5. https://pubmed.ncbi.nlm.nih.gov/32860505/