Pathophysiology of Arrhythmia

Introduction

Arrhythmias are abnormal heart rhythms caused by disturbances in the electrical conduction system of the heart. These disturbances can lead to irregular, too fast (tachycardia), or too slow (bradycardia) heartbeats. Understanding the pathophysiology of arrhythmia is essential for effective diagnosis and treatment.

Normal Cardiac Electrophysiology

The heart's electrical impulses originate in the sinoatrial (SA) node, often called the natural pacemaker. The impulse then travels through the atrioventricular (AV) node, the bundle of His, and finally into the Purkinje fibers, ensuring coordinated contraction of the heart.

Key Components of Cardiac Electrophysiology:

• Sinoatrial (SA) node: Initiates the heartbeat
• Atrioventricular (AV) node: Delays impulses to allow ventricular filling
• His-Purkinje system: Ensures synchronized ventricular contraction

Mechanisms of Arrhythmias

Arrhythmias arise due to abnormalities in impulse formation or conduction. The main mechanisms include:

1. Abnormal Impulse Formation

• Enhanced automaticity: Increased firing of pacemaker cells (e.g., sinus tachycardia, premature atrial contractions).
• Triggered activity: Extra impulses due to ionic disturbances causing afterdepolarizations (e.g., long QT syndrome, torsades de pointes).

2. Abnormal Impulse Conduction

• Reentry: An impulse circles around a circuit, causing repetitive activation (e.g., atrial fibrillation, ventricular tachycardia).
• Conduction block: Delay or interruption in impulse propagation (e.g., AV block).

Common Types of Arrhythmias

• Supraventricular arrhythmias (originate above the ventricles)
  • Atrial fibrillation (AF), Atrial flutter, AV nodal reentrant tachycardia (AVNRT)
• Ventricular arrhythmias (originate in ventricles)
  • Ventricular tachycardia (VT), Ventricular fibrillation (VF)
• Bradyarrhythmias
  • Sinus bradycardia, AV block

Conclusion

Arrhythmias occur due to disruptions in the heart’s electrical activity. Understanding their pathophysiology aids in effective diagnostics and treatment. Management includes medications, catheter ablation, or implantable devices like pacemakers or ICDs.

References

• For detailed recommendations, please refer to:
  • American Heart Association (AHA) Guidelines on Arrhythmias
  • European Society of Cardiology (ESC) Guidelines on Arrhythmias

Source recommendations

1. American Heart Association (AHA) Guidelines on Arrhythmias

1. https://www.heart.org/en/health-topics/arrhythmia
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
3. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia
4. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
5. https://pubmed.ncbi.nlm.nih.gov/29097294/

2. European Society of Cardiology (ESC) Guidelines on Arrhythmias

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
4. https://pubmed.ncbi.nlm.nih.gov/36017572/
5. https://www.ahajournals.org/doi/10.1161/01.cir.0000091380.04100.84