Most of us do not give our heartbeat a second thought. However, for over 10 million Americans, an irregular heart rhythm called atrial fibrillation (AFib) disrupts daily life. AFib is the most common heart arrhythmia worldwide. It occurs when improperly triggered electrical signals in the heart cause the atria, or upper chambers, to beat sporadically.
Some people with AFib have no symptoms, while others suffer from chest pain, palpitations, fatigue, and lightheadedness. More seriously, those with AFib have a five-times greater risk of stroke because the irregular rhythm can cause blood to collect, forming a clot that can travel to the brain.
AFib treatments aim to control heart rate or restore normal rhythm. Typically, oral medication is recommended first, but if ineffective, surgical treatments are often the next step.
Two of the most common procedures include catheter ablation and the Cox Maze, both of which create lesions of scar tissue to block faulty electrical signals and restore normal rhythm. As one electrophysiology engineer describes, ablation works like burning a firebreak to stop the spread of wildfire. The goal is to create a “wall” of scar tissue to stop faulty electrical signals from traveling through the heart.
In catheter ablation, a thin tube is guided through a vein into the heart, as shown in the image below. Looking at a map of the patient’s heart, the cardiologist identifies the location of tissue to be ablated. There are multiple types of catheter ablation; radiofrequency (RF) burns the targeted tissue, cryoablation freezes it, and pulsed field ablation (PFA) uses short, high-voltage electrical pulses instead of thermal energy. These procedures are becoming increasingly common, and Lars Thording from Innovative Health estimates that in 2020, 240,000 catheter ablations were performed to treat AFib in the US.
A study by Nakatani et al. comparing the mechanical effects of PFA and RF found that PFA produced larger, homogeneous lesions without the tissue bleeding often caused by RF therapy. Because PFA does not depend on heat transfer, the tissue’s thermal conductivity does not affect the therapy. Additionally, both methods caused an increase in tissue stiffness, but only the PFA-ablated tissue returned to its original elasticity levels. This suggests that heart tissue recovers better after PFA than RF ablation.
Catheter ablation is highly successful, but some patients unfortunately experience AFib recurrence after treatment. According to a recent meta-analysis on ablation therapy, the return of AFib can be caused by small gaps between lesions, allowing the faulty electrical signals to pass. In such cases, the Cox Maze procedure may be more effective.
The Cox Maze is an open-heart surgery producing a maze-like pattern of scar tissue. The first versions required cutting and resewing the heart, and the scar tissue was created with a scalpel. However, newer techniques use radiofrequency ablations to form lesions. A comparative control trial found that the new procedure resulted in reduced thickness of ablated tissue, shorter operation time, and a higher success rate.
Though more invasive, the meta-analysis referenced above states that the Cox Maze procedure is 1.85 times more likely than catheter ablation to successfully treat AFib without recurrence. Ultimately, both catheter ablation and the Cox Maze procedure represent major advances in managing this widespread arrhythmia and improving quality of life for millions.
If you are interested in learning more about catheter ablation or the Cox Maze procedure, please take a look at these articles for additional information.