Because of the shortcomings of fluoroscopy, some electrophysiologists (EPs) use electroanatomic mapping systems. The most common electroanatomic mapping systems for afib ablation are the Ensite NavX (Abbott) and CARTO (Biosense Webster). Each provides colorful 3D images that show variations in a patient’s anatomy.
Electroanatomic mapping systems may assist EPs in assuring that lesions are contiguous (no gaps). Additionally, they may reduce complications, such as perforation of the heart or esophagus. In addition, the use of an electroanatomic mapping system may lessen the time that EPs and patients are exposed to radiation. However, the systems are expensive, so they are not available at all facilities.
These systems create a real-time 3D view of the heart by positioning a mapping catheter in the heart. Then, when the EP moves the catheter in a sweeping motion, the systems track the catheter’s location. CARTO and Ensite NavX use different methods to do this.
The latest generation of the CARTO system, CARTO 3, uses an electroanatomic location pad located under the table where the patient lies. Six electrode patches, three on the patient’s back and three on the chest, track catheter movement and build a 3D map of a patient’s cardiac structures. The latest generation of the Ensite NavX system, Ensite Velocity, uses body-surface patch electrodes to construct the 3D cardiac map. The CARTO and NavX systems are compatible with various mapping catheters.
Electroanatomic mapping systems are sometimes called multi-modality mapping or image integration systems because they can show pictures or data from other sources. Typically, patient CT or MRI scans may be taken a few days or weeks before the procedure. Those scans can be loaded onto Ensite NavX or CARTO and matched with the real-time 3D image of the heart.
The EP does this by moving the catheter slightly, verifying its location in the heart, and taking note of large structures such as the pulmonary veins. After identifying several common areas on the two images, the system merges the real-time view and pre-procedure scan into a 3D picture. It takes about 15 minutes to complete this process, called registration. However, the positioning of the anatomy may have changed since the scan. Thus, if the pre-procedure scan doesn’t easily correspond with the real-time view of the heart, this process can take much longer.
Electroanatomic mapping systems provide real-time data on electrical activity within the heart. That means the EP can see whether the conduction block has been achieved. These systems also offer other real-time information, such as atrial pressure and volume, so the EP can easily monitor the patient during the procedure.
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The CARTO 3 and Ensite Velocity mapping systems are capable of high-density mapping through the addition of compatible software modules and multipolar catheters.
The newest electroanatomic mapping systems use multielectrode basket catheters to rapidly record electrical activity from thousands of points, which aids in making 3D maps more accurate. Basket catheters contain self-expanding splines containing many electrodes. The splines are arranged into a three-dimensional spheroid shape similar to that of a stretched balloon. This unique design enables the catheter to conform to the shape and movements of the heart chamber.
High-density mapping systems that use basket catheters include the AcQMap High Resolution Imaging and Mapping System and the Rhythmia HDx. These systems have the potential to further improve the safety and efficiency of catheter ablations.
AcQMap (Acutus Medical) High Resolution Imaging and Mapping System uses 3D ultrasound overlaid with high-resolution electrical activation maps to reconstruct the heart. The system uses dipole density mapping instead of the typical voltage mapping to provide a more detailed mapping. This includes the electrical activity across cell membranes and maps a wider area of the heart.
The system uses the AcQMap 3D Imaging and Mapping basket catheter. It is a non-contact catheter, meaning the basket catheter floats freely in the left atrium and doesn’t need to touch the surface of the heart to generate a map. The catheter contains 48 electrodes and can quickly create a 3D map by rotating around the atrium.
The UNCOVER AF trial used the AcQMap System in 127 persistent afib patients. The results showed freedom from afib at 12 months (either on or off antiarrhythmic drugs) for 73% from a single procedure and 93% from one or more procedures. There were no major adverse events related to the devices used.1 The RECOVER AF Trial is currently underway using the AcQMap System in recurrent afib.
Rhythmia HDx (Boston Scientific) high-density mapping system uses the Orion basket catheter. This catheter contains splines with 64 electrodes for cardiac mapping. The True-HD clinical study established that Rhythmia HDx was safe and effective. This study had 572 patients with various arrhythmias, including afib patients with previous unsuccessful afib ablations from other techniques. The study focused on immediate success rates, with one month of follow-up. Depending on the type of arrhythmia treated, success rates varied from 64% to 96%. In addition, the complication rate was low, with only three (0.57%) complications potentially related to the mapping catheter.2 These results showed that the Rhythmia HDx mapping system was a novel mapping method that was safe and effective. These results do not extend beyond one month.
In February 2017, the FDA cleared the CardioInsight Noninvasive 3D Mapping System (Medtronic), the first noninvasive electroanatomic mapping system in the US. The CardioInsight is a vest worn by the patient to collect real-time ECG signals. It uses 252 electrode sensors and combines these ECG signals with CT scan data to produce a 3D cardiac map of the heart. This was the first cleared device that could map activity in the heart without placing catheters in it.
To learn about advanced navigation systems, see Robotic Catheter Navigation.
To learn more about whether catheter ablation is appropriate for you, see Are You a Candidate for Catheter Ablation.
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