Atrial fibrillation (AF) is a common cardiac arrhythmia characterised by an irregular heart rhythm, which can cause various complications such as heart failure and stroke. Catheter ablation of the pulmonary veins is an effective therapy for patients suffering from paroxysmal atrial fibrillation (AF). However, medicine is lacking a reliable curative therapy for patients with persistent AF. Recently, catheter ablation targeting areas of low voltage identified by intracardiac mapping has gained attention as a promising approach for persistent AF patients. However, there is a lack of understanding and consideration of confounding variables that influence voltage but are not indicative of an arrhythmic substrate.One of the confounding factors is the size of the electrodes on the catheters.