Diagnosis of Atrial Fibrillation

Atrial fibrillation (AF) is diagnosed using any device that records the electrical activity of the heart on the principle of a voltmeter and displays this electrical activity as an ECG tracing:

• Smart devices with ECG (ECG watch, blood pressure monitor with ECG, ECG card)
• 12-lead ECG
• ECG Holter monitoring
• Implantable loop recorder

Smart devices with ECG record the electrical activity of the heart and generate a single-lead ECG; for example, a watch produces an ECG lead that corresponds precisely to lead I on a standard 12-lead ECG.

• In a 12-lead ECG, lead I is generated from two electrodes, one placed on the right arm and the other on the left arm.
• With an ECG watch, one electrode is located on the back of the watch on the wrist and the second electrode is the watch crown, which is touched with a finger of the opposite hand.

Using an ECG watch, it is technically possible to sequentially record a 12-lead ECG; however, the leads are not recorded simultaneously but sequentially. The ECG watch is successively placed on the chest, arms, and lower limb. In clinical practice, this is not routinely used, but it is technically feasible. If the ECG watch is placed on the chest at the position corresponding to lead V1, it is possible, for example, to diagnose a Brugada ECG pattern.

ECG tracing:

• In sinus rhythm, it displays atrial electrical activity as P waves.
• In AF, it displays atrial electrical activity as fibrillatory waves, as the atria are fibrillating.
• Ventricular electrical activity is displayed as QRS complexes.

For the diagnosis of AF, capturing AF on ECG is crucial; AF does not need to last 30 seconds, for example:

• A 12-lead ECG records 4 seconds of cardiac electrical activity (most commonly).
• An ECG from a watch records 30 seconds of cardiac electrical activity.
• A 24-hour ECG Holter records 24 hours of cardiac electrical activity.

AF is not diagnosed using devices that do not record the electrical activity of the heart, such as: a conventional blood pressure monitor, an oximeter, or smart devices that measure pulse based on photoplethysmography.

• However, if such devices raise suspicion of AF, the diagnosis must be confirmed using ECG.