Electrophysiology of the Heart

Introduction

The human heart functions as a powerful electrical pump, maintaining circulation by generating and conducting electrical impulses. Understanding the heart’s electrophysiology is crucial for diagnosing and treating various cardiac arrhythmias and other disorders.

The Electrical Conduction System

The heart's electrical system consists of specialized structures that generate and transmit electrical impulses:

1. Sinoatrial (SA) Node (The Natural Pacemaker)

   • Located in the right atrium.
   • Generates impulses at 60-100 beats per minute in a healthy adult.
   • These impulses travel to the atria, causing them to contract and push blood into the ventricles.

2. Atrioventricular (AV) Node

   • Found between the atria and ventricles.
   • Delays the electrical signal slightly, allowing the ventricles to fill with blood before contraction.

3. Bundle of His and Branches

   • Conduct impulses from the AV node to the ventricles.
   • Divides into right and left bundle branches to serve each ventricle separately.

4. Purkinje Fibers

   • Spread the electrical impulse through the ventricles, ensuring a coordinated contraction.

The Electrical Cycle of the Heartbeat

Each heartbeat follows a sequence of electrical events: 1. Impulse Generation – The SA node initiates an electrical impulse, acting as the heart’s pacemaker. 2. Atrial Contraction – The impulse spreads through the atria, causing them to contract and push blood into the ventricles. 3. Ventricular Activation – The signal reaches the AV node, travels through the Bundle of His, reaches the ventricles via Purkinje fibers, and triggers ventricular contraction. 4. Recovery Phase – The heart prepares for the next impulse by repolarizing, restoring its resting state.

Abnormalities in the Electrical System

Electrical disturbances can cause: - Bradycardia (slow heart rate) if the SA node fails. - Tachycardia (fast heart rate) due to abnormal impulse formation or conduction. - Atrial fibrillation (irregular atrial activity) leading to inefficient heart function. - Heart block (signal delay or interruption) potentially requiring a pacemaker.

Diagnosis and Treatment

Electrocardiograms (ECGs) are used to diagnose electrical issues. Treatment may involve medications, pacemakers, or catheter ablation to correct abnormal rhythms.

Conclusion

Understanding heart electrophysiology helps in managing arrhythmias effectively and ensures proper cardiovascular function. If you experience irregular heart rhythms, a cardiologist's evaluation is essential.

Source recommendations

1. American Heart Association 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/29084733/

2. European Society of Cardiology Guidelines on Cardiac Electrophysiology

1. https://www.escardio.org/
2. https://pubmed.ncbi.nlm.nih.gov/11583910/
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines
4. https://academic.oup.com/eurheartj/article/34/29/2281/401445
5. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death