The ECG Rhythms content is currently under development and is being updated by medical professionals.
Atrial fibrillation (AFib) is the most common sustained cardiac arrhythmia, characterized by chaotic and irregular electrical activity in the atria. This disorganized electrical activity leads to ineffective atrial contraction and an irregularly irregular ventricular rhythm. Multiple electrical impulses firing from various sites within the atria contribute to this chaotic pattern.
Analogy: “A disorganized flurry of musical notes played randomly by the upper section of the orchestra.”
The ECG in atrial fibrillation typically reveals an irregularly irregular ventricular rhythm, meaning the time intervals between consecutive QRS complexes (RR intervals) vary unpredictably. Distinct P waves are absent, replaced by rapid, low-amplitude, and irregular fibrillatory waves (f waves) that reflect the chaotic electrical activity within the atria. These fibrillatory waves may be fine or coarse and are often best seen in lead V1. The ventricular rate can vary widely depending on the ability of the AV node to conduct the rapid atrial impulses, and it may be rapid (100-175 bpm) or slow. The QRS complexes are usually narrow, unless there is a pre-existing bundle branch block or an accessory pathway is involved.
Many individuals with atrial fibrillation may initially be asymptomatic. However, when symptoms do occur, they can include palpitations, often described as a fast, fluttering, or pounding heartbeat, shortness of breath, fatigue, dizziness, lightheadedness, and chest pain. Atrial fibrillation significantly increases the risk of blood clot formation within the atria, particularly in the left atrial appendage, which can lead to stroke or other thromboembolic events. The risk of developing AFib increases with age and is also elevated in individuals with other heart conditions, high blood pressure, excessive alcohol consumption, caffeine or nicotine use, and certain electrolyte imbalances.
“Like a crowd of musicians playing different tunes at once without a conductor, the atria are firing electrical signals in a chaotic manner.”