Over the past decade, significant advances have been made in the realm of arrhythmia management due to expansion of interest in catheter-based solutions to reduce the morbidity associated with these disease states. Growth in this field has propelled research and development of force-sensing catheters as well as high-density mapping catheters such as the Advisor HD Grid Mapping Catheter, Sensor-Enabled (Abbott) (Figure 1). Significant improvements in diagnostic and therapeutic tools, as well as a better understanding of pathophysiology, has helped to improve clinical outcomes while reducing procedural duration and radiation exposure. Specifically, the use of the Advisor HD Grid has certainly increased our workflow and efficiency while also improving accuracy and precision.
High-density mapping has been described most commonly for scar-related ventricular tachycardia. However, we have been able to utilize this mapping in atrial arrhythmias as well. The Advisor HD Grid provides an excellent solution for waveform directionality bias when bipolar timing, activation, and fractionated maps are desired. We believe the electrograms seen on this catheter are unparalleled and can be attributed not only to the ability of the EnSite Precision Cardiac Mapping System (Abbott) to display and collect data from orthogonal bipolar electrograms simultaneously at the same site, but are also due to shape of the catheter and layout of the electrodes. As the name implies, it employs a “grid” of very small electrodes (1 mm each) in a four-by-four pattern or grid on 2.5 Fr splines. Each electrode is spaced 3 mm apart (edge to edge). Unlike other catheters that may cause the chamber walls of anatomic models to deform to the shape of the catheter, the Advisor HD Grid acts as a “paintbrush.” It can be navigated easily and creates very little ectopy.
Our standard workflow is centered around the utilization of three-dimensional mapping with the EnSite Precision in conjunction with the Advisor HD Grid and ViewFlex Xtra Intracardiac Echocardiography (ICE) Catheter (Abbott). With these tools, we have been successfully able to perform the majority of our cases, both atrial and ventricular, without any fluoroscopy or radiation exposure. We have been fluoroless for the past 5 years. The only cases that have required a small amount of fluoroscopy have traditionally been epicardial ventricular tachycardia and congenital heart cases. For example, we describe a brief case of a congenital patient with dextro-Transposition of the great arteries status post Mustard procedure with baffle driven atrial flutter. (See sidebar)
We have used the Advisor HD Grid in approximately 60 procedures of all arrhythmia types in all chambers, including the epicardial space for ventricular tachycardia. It has been useful for mapping focal and reentrant ventricular tachycardias, PVCs, atrial fibrillation, typical and atypical atrial flutters, AVNRT, and even in accessory pathways. Regarding the latter, as it is not uncommon to encounter tangential pathways. The EGMs collected and displayed on the Advisor HD Grid have given us a new and enhanced view of the activation sequence over the area of interest with more speed than utilizing a traditional linear bipolar catheter.
Since the release of EnSite Precision, we have used the AutoMap feature on every ablation to automatically collect and display activation and voltage maps. After comparing manual point collection and editing with AutoMap, we were convinced of its validity. Due to the reliable data collected by the catheter and displayed on the EnSite Precision, some features on the system can be utilized in ways not yet explored. One of these is the use of SparkleMap during electroanatomic data collection. The SparkleMap feature is a way of displaying the activation of a given map by “sparkling” the points in order of activation by the appearance of small white spheres in sequence. It can then be overlaid on any other existing map, making the activation pattern apparent while mapping is still in progress. With it, we can visually appreciate and identify areas of suspected arrhythmias due to slowing or breakout, and mark these areas with tags.
Our approach to an atrial arrhythmia case begins with mapping of the venous system starting at the entry site in the femoral vein all the way up to the heart itself. We use a Livewire Duo-Decapolar 2-10-2 mm spaced catheter (Abbott) to initially map the venous system. Once in the heart, we spin the catheter, taking precaution in patients with known leads inside their heart, to obtain a geometry of the right atrium as well as the superior and inferior vena cava (IVC). Once this is done, the catheter tip is placed deep into the coronary sinus with a large loop abutting the crista terminalis at electrodes 11-20. In the case where the coronary sinus is not patent or not found, a large loop with the catheter is placed entirely inside the right atrium.
Next, we advance the Advisor HD Grid to the right atrium and collect detailed anatomical information. Voltage, fractionation, and activation data are also simultaneously collected and compiled. If the patient presents in sinus rhythm, we focus on the voltage map to identify areas of lower voltage suggesting scarring in order to determine if this substrate is crucial to our arrhythmia initiation and propagation. If the patient presents in an atrial arrhythmia other than atrial fibrillation, we start with the voltage map, then overlay the fractionation index at a level of 3 to determine if the areas of lower voltage are related to the areas of highest fractionation. We then play the activation and propagation maps to find the areas of slowest conduction. If a reentrant circuit is suspected, we will use the 12-lead EKG to determine the diastolic window and locate the areas of slow conduction that are also mid-diastolic. In a focal arrhythmia, we identify the earliest activation and overlay the voltage map to determine if this is in an area of lower voltage. If so, this area is targeted for ablation. Videos 1, 2, and 3 demonstrate how this is done.
Our mapping strategy for ablation is slightly different if the patient arrives in atrial fibrillation. We rely more heavily on the substrate mapping with voltage and the fractionation index. The Advisor HD Grid is very useful to quickly and easily map the left atrium as well. The left pulmonary veins and left atrial appendage (LAA) are usually easily mapped with the Advisor HD Grid. The body of the left atrium is also usually easily mapped due to the bidirectionality of the Advisor HD Grid, and in conjunction with an Agilis deflectable sheath (Abbott), it is rare not to be able to create a high-density map of the entire left atrium in a fast and efficient manner. The right pulmonary veins can take a little more effort due to the retroflexion of the Advisor HD Grid, but the soft architecture of the catheter allows this to be performed safely and easily as well. Following 3D mapping, we utilize a TactiCath Quartz Contact Force Ablation Catheter (Abbott) to achieve a wide area circumferential ablation around the pulmonary veins or a pulmonary vein isolation approach. Next, we target the area(s) bisected on our combination maps revealing low voltage and high fractionation index. We recreate our maps live during the case and modify them as well. In more than 50% of our cases, we organize the atrial fibrillation into an atypical flutter rhythm and are then able to utilize our flutter ablation techniques (as discussed above) with much success.
This article was published with support from Abbott.
Acknowledgements: Dr. Yoo would like to thank Aaron Stammer and Carrie Pottmeyer from Abbott Medical for their assistance with this article.
Disclosure: Dr. Yoo has no conflicts of interest to report regarding the content herein. Outside the submitted work, he reports training and consulting honorariums from Abbott.