Atrial Fibrillation: Characteristics and ECG Manifestation

Introduction

Atrial fibrillation (AF) is a prevalent cardiac arrhythmia characterised by irregular and rapid electrical activity in the heart's upper chambers, known as the atria. Understanding its features and ECG manifestation is crucial for diagnosis and management.

Characteristics of Atrial Fibrillation

• Irregular Rhythm: AF disrupts the normal coordinated contraction of the atria, resulting in irregular and varied time intervals between consecutive QRS complexes (RR intervals).
• Absent P Waves: Instead of the normal upright P wave representing atrial depolarization, the ECG shows rapid, irregular, and lower amplitude fibrillatory waves. These chaotic and irregular waves replace the P waves and exhibit variations in shape, amplitude, and frequency, reflecting disorganized electrical activity within the atria.
• QRS Complex: The duration of the QRS complex, representing normal ventricular depolarization, typically falls within the normal range, i.e., less than 0.12 seconds. However, in the presence of underlying conduction abnormalities or accessory pathways, the QRS complex duration may be prolonged.
• Variable Ventricular Response: The ventricular rate in AF can vary, depending on the conduction properties of the atrioventricular (AV) node and the influence of factors such as medications. The ventricular rate may be normal, slow (bradycardia), or rapid (tachycardia).

ECG Manifestation of Atrial Fibrillation

On an ECG, AF is identified by:

• Absence of P Waves: The normal P wave is absent, replaced by fibrillatory waves reflecting chaotic atrial electrical activity.
• Irregular Rhythm: The irregularly irregular RR intervals signify the hallmark of AF.
• Variable Ventricular Response: The ventricular rate may show fluctuations ranging from normal to slow or rapid.

Importance of Accurate Diagnosis

Accurate diagnosis of AF is crucial due to its clinical implications and associated risks. Specific treatment strategies, such as blood-thinning medications, may be necessary to manage the increased risk of blood clots, stroke, and heart failure.