How is ventricular fibrillation diagnosed?

Ventricular fibrillation (VF) is typically diagnosed using an electrocardiogram (ECG), a noninvasive test that records the heart's electrical activity. In sinus rhythm, the ECG shows a consistent pattern of electrical impulses originating from the sinoatrial node (SA node), which is located in the right atrium. When VF occurs, the ECG shows rapid and chaotic electrical activity originating from multiple sites within the ventricles, leading to an irregular and ineffective heartbeat.

Key features observed on the ECG during VF include:

1. Absence of organized QRS complexes: The characteristic QRS complexes, which represent ventricular contraction, are absent in VF.

2. Fibrillatory waves: VF is characterized by rapid, irregular, and disorganized electrical activity, resulting in fibrillatory waves on the ECG. These waves have varying shapes, sizes, and durations, creating a chaotic pattern.

3. Absence of P waves and distinct ST segments: The P waves (representing atrial contraction) and distinct ST segments (representing the period between ventricular depolarization and repolarization) are not identifiable in VF.

4. Rate: The heart rate during VF is typically very rapid, ranging from 200 to over 300 beats per minute. This rapid and irregular rhythm is ineffective in generating meaningful cardiac output.

When the ECG shows the characteristic findings of VF, it becomes the primary tool for diagnosing this arrhythmia. Prompt recognition and diagnosis are crucial, as VF is considered a medical emergency and requires immediate defibrillation to restore a normal heart rhythm.