Pulsed-field ablation for atrial fibrillation

Atrial fibrillation is an irregular contraction of the upper chambers of the heart (atria) and often causes the heart to beat rapidly. This makes the heart less effective at moving blood from the upper to the lower chambers of the heart. Symptoms include palpitations, dizziness, shortness of breath, fatigue and chest pain. It can have a substantial effect on quality of life. Complications of atrial fibrillation include stroke and heart failure. Atrial fibrillation can be transient (paroxysmal), lasting longer than 30 seconds but only up to 7 days or it can be persistent, lasting more than 7 days.

Standard treatments for symptomatic atrial fibrillation include lifestyle modification, drug therapy and procedural interventions. The aim of treatment is to prevent complications like stroke and alleviate symptoms. Drug treatments include anticoagulants to reduce the risk of stroke, and antiarrhythmics to restore or maintain the normal heart rhythm or to slow the heart rate. When medications do not work or are unsuitable, other treatments such as catheter ablation procedures may be used. The current standard catheter ablation techniques are radiofrequency ablation (RFA) and cryoballoon ablation (CBA). Laser balloon ablation is rarely used in the NHS.

Atrial fibrillation is the most common heart rhythm disorder, affecting about 2% of the adult population. The prevalence is likely increasing because it is associated with age, underlying heart disease, diabetes, obesity and hypertension, which are also increasing in prevalence in the UK population. If left untreated, it is a significant risk factor for stroke, other morbidities and mortality. When standard medications do not work or are unsuitable, catheter ablation procedures are commonly offered. Most catheter ablation methods use thermal energy, by either burning (in RFA) or freezing (in CBA) heart tissue that conducts the irregular electrical impulses. Thermal ablation carries a risk of damaging neighbouring tissues. Pulsed-field ablation (PFA) uses electrical instead of thermal energy. Heart cells are very sensitive to electrical energy. So, it may be able to target heart tissue more precisely than thermal ablation, which may reduce the risk of damaging surrounding tissues like the oesophagus, nerves, and blood vessels.

PFA is a catheter ablation technique that uses electrical energy to destroy the heart cells that transmit abnormal electrical impulses. In the NHS, the procedure is usually done under general anaesthesia but deep sedation is often used in other countries. As in other catheter ablation procedures for atrial fibrillation, a catheter is inserted into the femoral vein and advanced into the left atrium through a trans‑septal puncture. The PFA catheter delivers rapid, high-voltage pulsed electrical energy to the tissue it is applied to. This causes pores to form in myocardial cells so they die (irreversible electroporation). Most commonly, PFA is used for isolation of abnormal electrical activity transmitted through the pulmonary vein cells at the entrance to the left atrium. But it can be used on other structures such as the left atrial posterior wall. The aim is targeted destruction and scar formation in the tissue it is applied to, to disrupt the transmission of abnormal electrical impulses that cause atrial fibrillation while avoiding damage to surrounding tissues such as nerves and blood vessels.