Understanding the V1 Lead in ECG

Introduction

The V1 lead is one of the precordial (chest) leads in an electrocardiogram (ECG) and plays a crucial role in diagnosing heart conditions. It is placed at the fourth intercostal space to the right of the sternum and provides valuable information about the electrical activity in the right ventricle and the septal region of the heart.

Role of Lead V1 in ECG Interpretation

1. Normal ECG Patterns in V1

• In a healthy heart, the P wave is usually positive or biphasic.
• The QRS complex is predominantly negative (rS or QS pattern) due to the direction of ventricular depolarization.
• T waves can be variable – slightly positive, negative, or flat.

2. Significance in Cardiac Diagnoses

• Myocardial infarction (MI): ST elevation in V1 could indicate septal or anterior MI.
• Right ventricular hypertrophy (RVH): A tall R wave in V1 may occur due to increased right ventricular pressure.
• Right bundle branch block (RBBB): Characterized by an rSR' pattern with a wide QRS complex.
• Supraventricular tachycardia (SVT): Pseudo-R' waves in V1 may be present in certain types of SVT.
• Brugada syndrome: A coved ST elevation in V1 with a right bundle branch pattern is a diagnostic feature.
• Wolff-Parkinson-White Syndrome (WPW): A delta wave (slurred upstroke in QRS complex) might be visible in V1.

Clinical Application

Physicians use lead V1 to detect and monitor various cardiac pathologies, including conduction abnormalities and life-threatening conditions like Brugada syndrome. In emergency situations, V1 is one of the key leads to assess arrhythmias and acute coronary syndromes.

Conclusion

Understanding the V1 lead in ECG interpretation is critical in recognizing various cardiac disorders. If an abnormal pattern is detected in V1, further evaluation including serial ECGs, echocardiography, and cardiac MRI may be warranted based on clinical suspicion.

Source recommendations

1. American Heart Association Guidelines on ECG Interpretation

1. https://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
2. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191095
3. https://www.heart.org/-/media/files/affiliates/mwa/kansas-city/kc-cardiac-and-stroke-symposium/2020-event-documents/cardiac-presentations/2-ecg-hockstad.pdf?la=en
4. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191098
5. https://pubmed.ncbi.nlm.nih.gov/19281931/

2. European Society of Cardiology Guidelines on ECG and Arrhythmia Diagnosis

1. https://www.escardio.org/static-file/Escardio/Guidelines/Documents/ehaa612.pdf
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines
4. https://academic.oup.com/eurheartj/article/39/21/1883/4939241
5. https://www.jacc.org/doi/10.1016/j.jacc.2024.10.080