Catheter Ablation Technology
The goal of any catheter or energy source is to create a transmural lesion while minimizing complications. A transmural lesion—scar tissue that completely penetrates the heart tissue—is key to a successful ablation because it keeps errant electrical signals from being transmitted.
Making a transmural lesion is as much of an art as it is a science. It depends on the temperature generated by the energy source, how much pressure is applied to the catheter (contact force), and how long the catheter remains in contact with tissue. There are different energy sources that can be used in various types of catheters, and each has advantages and disadvantages, so it's important for patients to understand the different options.
Here are the energy sources being used today in atrial fibrillation catheter ablations:
Radiofrequency (RF) energy is radio waves that are converted to heat to ablate and create scar tissue. It reliably achieves transmurality and is the most widely used energy source in catheter ablations. In general, high temperatures are needed to make sure that all layers of tissue are ablated. Traditional catheters use unipolar radiofrequency energy, which simply means that the radiofrequency energy is transmitted from a single point at the catheter's tip.
Cryothermy, or cryo energy, is intense cold that is used to form ice crystals within the tissue, causing the cells to die and creating scar tissue. It may be easier to make lesions using cryothermy since the cold temperatures cause tissue to stick to the catheter. In addition, cryo energy may have fewer major complications. Animal studies have shown cryo energy to have a much lower incidence of thrombus (clot) formation than radiofrequency energy, which suggests that cryothermy could lower the risk of a stroke. Cryo energy can be used in single point catheters or balloon catheters.
Laser energy is light waves that are converted to heat to ablate and create scar tissue. It may be a safer heat-based energy than unipolar radiofrequency energy. With laser energy, the catheter doesn’t need to be in direct contact with tissue, which could mean it will have fewer complications than radiofrequency energy. Unlike other energy sources, contact force is not a factor in whether a laser lesion is transmural. In addition, laser energy can be adjusted when ablating tissues of varying thickness, with higher energy applied to thicker tissue and lower energy applied to thinner structures in the heart.
The design and functionality of catheters is constantly evolving. Most atrial fibrillation ablations today use single point radiofrequency energy catheters, which have a success rate—freedom from atrial fibrillation—of about 70%. It’s believed that different types of catheters could have higher success rates or fewer complications. Here are the different types of catheters available today for atrial fibrillation catheter ablations:
Single point radiofrequency catheters emit radiofrequency energy from a single point at the catheter tip. To make lesions, electrophysiologists ablate one spot after another, similar to drawing a line by making dots one after the other. If all the dots are not connected, afib could re-enter the heart in the unablated space (gap).
Multielectrode radiofrequency catheters have several electrodes, each of which can transmit radiofrequency energy. These catheters can ablate a larger area of tissue than single point radiofrequency energy catheters, which could decrease procedure times. In addition, multielectrode catheters may be better at making contiguous lesions (lesion lines without any gaps) than single point catheters. Finally, these catheters enable the use of bipolar radiofrequency energy, which may reduce certain complications that are seen with unipolar radiofrequency energy. However, there is limited clinical data on multielectrode catheters, which means that complications arising from these procedures may not be fully known or understood.
Contact force sensing radiofrequency catheters. Contact force is one of the variables that affects transmurality. If there is not enough pressure, the lesion may not fully penetrate the tissue, which would allow afib to re-enter the heart. If there is too much pressure, complications, such as steam pops, can occur. These catheters tell the electrophysiologist how much pressure is being applied to the catheter and tissue.
Balloon catheters. After the balloon catheter is inserted into the left atrium, the electrophysiologist inflates the balloon at the tip of the catheter. Balloon catheters can ablate a larger area of tissue than single point radiofrequency catheters, which enhances the prospects that lesions will be contiguous (without gaps) and could shorten procedure times. There are balloon catheters using cryothermy, laser energy, and even radiofrequency energy. In general, balloon catheters have difficulty reaching the right pulmonary veins.
To learn more about catheters used in atrial fibrillation treatment, see Single Point Radiofrequency Catheters, Multielectrode Radiofrequency Catheters, Contact Force Sensing Radiofrequency Catheters, and Balloon Catheters.
To learn more about whether catheter ablation is appropriate for you, see Are You a Candidate for Catheter Ablation.
Disclaimer: Some companies mentioned on this site may be donors to StopAfib.org but do not receive favored treatment in coverage as atrial fibrillation patients are our first priority.