**1. Introduction**

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. AF is associated with a higher risk of mortality, and it is one of the major causes of stroke, heart failure, sudden death, and cardiovascular morbidity worldwide [1, 2]. Thus, appropriate management of this arrhythmia and underlying diseases is essential.

Catheter ablation is the cornerstone of the rhythm control treatment of AF by isolating the pulmonary veins from the left atrium (pulmonary vein isolation; PVI). During this procedure, creating a contiguous and durable lesion set is essential to achieve good long-term results [3, 4]. When applying radiofrequency (RF) ablations, the lesions are created in two phases: resistive and conductive heating of the myocardial tissue [5]. Both the ablation catheters and the generators have undergone impressive technical developments to reach homogenous and good-quality lesion creation. Despite recent years' technological developments, the durable isolation of the pulmonary veins remains a challenge. Moreover, procedural complications also remained a significant issue [6–8].

Nowadays, the use of high-power (HP) radiofrequency applications is in the center of scientific research. High-power, short-duration (HPSD) ablation might result in a more uniform, transmural lesion set [9]. Thus, it can reduce procedure time and seems to be non-inferior compared to low-power (LP) ablation. This technique was associated with a better clinical outcome, possibly due to the better durability of PVI [10]. Multiple clinical studies have proven the safety and efficacy of high-power, short-duration PVI for AF ablation.

In this chapter, we will introduce the theoretical background of HPSD ablation, and we also aim to discuss the main differences with low-power ablations, also mentioning some relevant clinical trials.
