Sinus Arrest on ECG

Introduction

Sinus arrest is a condition where the sinoatrial (SA) node, the natural pacemaker of the heart, temporarily stops generating electrical impulses. This can cause pauses in the heart's rhythm, leading to dizziness, fainting, or even more severe complications.

ECG Characteristics of Sinus Arrest

1. Absent P waves: A sinus pause occurs when the SA node fails to produce an impulse, leading to missing P waves.
2. Irregular pause: The duration of a sinus pause is not a multiple of the normal P-P interval (unlike sinus exit block, where the timing remains consistent).
3. Resumption of sinus activity: After the pause, the sinus node may resume normal function or allow an escape rhythm to take over.

Symptoms and Clinical Significance

• Many short sinus pauses are asymptomatic.
• Longer pauses (more than 3 seconds) may cause dizziness, syncope (fainting), or fatigue.
• If prolonged, sinus arrest may indicate sinus node dysfunction (sick sinus syndrome), requiring further evaluation and potential pacemaker implantation.

Possible Causes

• Intrinsic SA Node Dysfunction (e.g., sick sinus syndrome, fibrosis of the SA node)
• Extrinsic Causes:
  • Medications (e.g., beta-blockers, calcium channel blockers, antiarrhythmics)
  • Increased vagal tone (e.g., during sleep, in athletes, or due to carotid sinus hypersensitivity)
  • Electrolyte imbalances (e.g., hyperkalemia)
  • Myocardial infarction affecting the sinus node

Diagnosis and Management

• ECG Monitoring: A 12-lead ECG or Holter monitor helps detect sinus arrest episodes.
• Medical Management:
  • Adjust medications if drug-induced.
  • Treat underlying causes (e.g., correcting electrolyte disturbances, managing myocardial ischemia).
  • If symptomatic and severe, a pacemaker may be needed.

Conclusion

Sinus arrest is a potentially serious condition detected by ECG as an irregular pause without a consistent pattern. If persistent or symptomatic, it requires further evaluation and management. If you suspect sinus arrest, consult a cardiologist for proper assessment.

Source recommendations

1. American Heart Association Guidelines on Bradyarrhythmias

1. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate
2. https://cpr.heart.org/-/media/cpr-files/cpr-guidelines-files/algorithms/algorithmacls_bradycardia_200612.pdf
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
4. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms
5. https://pubmed.ncbi.nlm.nih.gov/30586772/

2. European Society of Cardiology Guidelines on Cardiac Pacing and Resynchronization Therapy

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
2. https://academic.oup.com/eurheartj/article/42/35/3427/6358547
3. https://pubmed.ncbi.nlm.nih.gov/34455430/
4. https://academic.oup.com/eurheartj/article/34/29/2281/401445
5. https://pubmed.ncbi.nlm.nih.gov/23801827/