A new treatment for atrial fibrillation

In a recent post (Quantification of atrial fibrillation risks), I described a new study that showed that the incidence rate of atrial fibrillation (AFib) in a Danish population had increased from 24.2% in the period 2000-2010 to 30.9% in the period 2011-2022. Complications from AFib included heart failure (approximately 2 in 5) and stroke (approximately 1 in 5). Given these health risks, an important question is what are the treatments for atrial fibrillation?

The main treatments for atrial fibrillation (AFib) strive to control heart rate, restore normal heart rhythm, reduce symptoms, and prevent complications like stroke. The treatment strategy may include:

• Rate Control: Medications such as beta-blockers (e.g., metoprolol), calcium channel blockers (e.g., diltiazem), and digoxin are used to control the heart rate. These help to manage symptoms and improve heart function.
• Rhythm Control: Medications to restore and maintain a normal heart rhythm include antiarrhythmic drugs like amiodarone, sotalol, and flecainide. In some cases, procedures like cardioversion may be employed.
• Cardioversion comes in two types: Electrical cardioversion involves delivering a controlled electrical shock to the heart to restore a normal rhythm. Pharmacological cardioversion uses medications to try to restore a normal rhythm.
• Catheter ablation: This minimally invasive procedure uses heat or cold energy to create small scars in the heart tissue, blocking the abnormal electrical signals that cause AFib. For example, radiofrequency energy or freezing (cryoablation) create scar tissue within the heart. It is the same general concept as the maze surgical procedure described next.
• Surgery: In some cases, a surgical procedure called a maze procedure may be recommended. This open-heart surgery creates a pattern of scar tissue in the upper chambers of the heart, preventing the chaotic electrical signals that cause AFib. An alternative procedure is left atrial appendage closure which blocks off a small pouch in the left atrium where blood clots can form, reducing the risk of stroke in AFib patients.
• Anticoagulation: Since AFib increases the risk of forming blood clots, leading to strokes, anticoagulant medications (blood thinners) like warfarin, dabigatran, apixaban, and rivaroxaban are often prescribed to prevent this complication.
• Lifestyle Changes: Managing risk factors by maintaining a healthy weight, regular exercise, avoiding excessive alcohol and caffeine, quitting smoking, and managing stress, high blood pressure, and cholesterol can also be beneficial.

The choice of treatment depends on several factors, including the type of AFib, symptoms, underlying causes, and the presence of other medical conditions. Doctors tailor treatment plans to best fit the individual patient’s needs.

A new procedure not listed above is Pulsed Field Ablation (PFA). PFA uses short electrical field pulses to disrupt the cell membrane of the heart tissue (termed electroporation), leading to cell death and scar formation. This technique is non-thermal, meaning it does not rely on heat or cold to affect the tissue. The electrical pulses cause irreversible electroporation, which selectively targets the cardiac cells while minimizing damage to surrounding tissues.

PFA is most similar to catheter ablation; both are minimally invasive procedures (i.e. catheter) that aim to create scar tissue at certain positions in the heart to block the abnormal electrical pathways causing AFib. PFA does so using a different, possibly safer method (electroporation) that reduces the risk of collateral damage to surrounding structures like the esophagus, pulmonary vein, and the phrenic nerve. Electroporation specifically targets cardiac tissue because of their electrical properties, and thus minimizes the risk of injuring non-cardiac tissue (e.g. esophagus).

The main disadvantage of PFA is that it is a new technology, and so it not yet widely available. In December 2023, the FDA approved the first PFA system (PulseSelect, Medtronic) for the treatment of paroxysmal (intermittent) and persistent atrial fibrillation (Figure 1). In addition, there is little to no long-term clinical data on its efficacy and safety compared to alternative treatments such as catheter ablation.

A recent study by Reddy et al. (2021) showed that the 1-year Kaplan-Meier estimates for freedom from any atrial arrhythmia was about 80% for 121 treated patients. There were only three adverse events: 2 pericardial effusions or tamponade (fluid buildup in pericardial cavity), and 1 hematoma). These results were consistent with other trials that have indicated that PFA might have a better safety profile and similar or superior efficacy compared to traditional ablation methods. Longer-term studies are needed to examine how many patients remain arrhythmia free for more than a year. Over time the efficacy and safety of the technology is expected to improve.

Figure 1. Design of the Medtronic PulseSelect PFA system. A. The 9 electrode array unspools and dilates from the catheter once positioned at the target area in the heart. B. There, it can deliver electric field pulses that cause electroporation (lesion) of the neighboring cardiac tissue (Medtronic).