Multi-electrode mapping (MEM) has immensely improved mapping of complex atrial and ventricular tachycardias and atrial flutters. The advantages of multi-electrode mapping include quicker and more accurate map creation. Several tools are available for MEM. In this article, we describe multi-electrode mapping utilizing the Advisor™ HD Grid Mapping Catheter, Sensor Enabled™ (Abbott).
ABOUT THE TECHNOLOGY
The Advisor HD Grid offers a first-of-its kind electrode configuration for high-density mapping. With its 3 mm equidistant electrode spacing, the catheter enables extremely rapid mapping times and point collection when used in conjunction with the AutoMap and TurboMap features of the EnSite Precision™ Cardiac Mapping System (Abbott). The catheter can collect points regardless of wavefront directionality due its ability to “see” points orthogonally, thus eliminating “bipolar blindness”. The ability to collect points orthogonally allows more accurate mapping information to be displayed, whether it be voltage or timing.
Besides mapping accuracy, model creation has also improved with the Advisor HD Grid. Because the catheter is sensor enabled, it takes advantage of magnetic points along with impedance points, resulting in a more geometrically accurate model of both the atrium and ventricle.
Moreover, with the catheter’s mapping portion being so pliable, it adheres to the wall of the heart’s chambers without distorting anatomy in comparison to traditional circular mapping catheters. Thus, “push points” is a rare occurrence with the Advisor HD Grid.
Catheter handling is made easy due to its design being based on the FlexAbility™ Ablation Catheter platform (Abbott). The catheter currently comes in the D-F curve, allowing maneuverability and reachability in any chamber of the heart.
Here we describe three challenging clinical scenarios in which the unique features of the Advisor HD Grid helped to identify the complex circuits and improve ablation outcomes.
CASE #1: ATYPICAL LEFT ATRIAL FLUTTER
A 60-year-old male with a history of persistent atrial fibrillation and previous pulmonary vein isolation presented with atypical flutter.
After transseptal puncture, the Advisor HD Grid was utilized for mapping of the left atrium. Mapping with the Advisor HD Grid allowed us to quickly create left atrial geometry while simultaneously collecting voltage and timing data. Mapping revealed that the pulmonary veins were isolated. The atrial flutter was quite complex to map, since there was significant scar in the left atrium. The high quality of the Advisor HD Grid signals, along with the best duplicate algorithm and adjustable AutoMap settings, allowed for rapid collection and interpretation of mapping data. The mapping proved re-entry to be at the level of the anterior mitral isthmus. Ablation at the mitral isthmus resulted in termination of the atrial flutter, and rendered it non-inducible. The Advisor HD Grid simplified the procedure and shortened case time by quickly collecting both mapping and model data, especially in areas of low voltage, where electrograms are typically quite difficult to interpret. (Figures 1-3)
CASE #2: PAPILLARY MUSCLE VT ABLATION
A 61-year-old female presented with wide complex tachycardia. EKG during tachycardia was suggestive of papillary muscle ventricular tachycardia (VT). Ejection fraction was preserved on echo, and cardiac MRI did not demonstrate any late enhancements to suggest scar. In the EP lab, monomorphic VT with right bundle branch block (RBBB) morphology was inducible, suggestive of posterior papillary muscle origin based on EKG criteria.
The left ventricle (LV) was accessed via a transseptal approach. The Advisor HD Grid was introduced into the left ventricle via a large curve Agilis™ sheath (Abbott) for high-density mapping with geometry creation.
The Advisor HD Grid’s conformability to all surfaces allowed for rapid geometry collection and separation of the papillary muscles from the LV surface model (Figures 4-6). Mapping was performed during the tachycardia. With the Advisor HD Grid, multi-electrode and HD mapping with AutoMap morphology matching were completed relatively quickly. We were able to obtain activation points without causing ectopy. The unique geometry of the Advisor HD Grid conformed on the papillary muscle, allowing us to map different segments around the muscle. We were able to quickly identify the origin of the VT and successfully ablate with no complications.
CASE #3: PERSISTENT AFib
A 78-year-old female presented with a history of the Cox-Maze procedure and persistent atrial fibrillation. After transseptal puncture, detailed mapping of the left atrium was performed using the Advisor HD Grid. Pulmonary veins were connected despite a previous Cox-Maze procedure. Even though voltage was low, the Advisor HD Grid helped to identify signals within the connected pulmonary veins. Pulmonary vein isolation was performed on the reconnected veins. Once the pulmonary veins were isolated, attention was directed towards the incompletely isolated posterior box wall. With box isolation, the patient’s atrial fibrillation organized into an atypical flutter. With the Advisor HD Grid, we observed some interesting findings. Even though the rest of the left atrium (including the coronary sinus) was in a slower flutter at a cycle length of 380 ms, a high degree of rotational activity and fractionated electrograms were detected just anterior to the left atrial appendage using the Advisor HD Grid. Ablation in this area resulted in termination of the atrial fibrillation and flutter. With pacing on high doses of isoproterenol, another flutter was inducible. Entrainment and activation mapping confined the circuit in the ridge between the left atrial appendage and left pulmonary veins. Ablation here resulted in termination of this flutter as well. Lesions were then extended to the valve to incorporate the abnormal substrate. No tachycardia was inducible following that lesion set. (Figures 7 and 8)
The Advisor HD Grid has truly changed our workflow for rapid multi-electrode mapping of complex substrates and tachycardias. We have now adapted the Advisor HD Grid as our catheter of choice for complex atrial and ventricular arrhythmias. There are several reasons for this.
Conformability of the Advisor HD Grid to the surface helps to confirm tissue contact while also reducing the need for geometry editing due to a lack of distention and push points. The soft catheter design helps to achieve higher electrode contact in different areas of the left atrium, thus improving accuracy of the map and allowing for a better understanding of the ablation substrate. Sixteen electrodes placed in a grid configuration are able to provide highly accurate and dense locations as well as timing information. The Advisor HD Grid also has equidistant spacing, allowing HD Wave bipolar recording along and across splines designed to remove bias created by wavefront direction during substrate mapping. A small surface area of 1 mm electrodes improves EGM quality. In addition, uniform spacing along and across the splines allows for collection of orthogonal bipolar electrodes, which both improves voltage mapping data and reveals circuits in activation maps.
Use of EnSite Precision in conjunction with the Advisor HD Grid identifies the highest amplitude EGM for each set of orthogonal bipolar electrodes. The SparkleMap feature can overlay live activation wavefront on the voltage map, helping us to better understand the arrhythmia mechanism.
Finally, utilization of intracardiac echo is routine for our ablation procedures. Due to its unique shape and configuration, the Advisor HD Grid can be clearly visualized on ICE to confirm tissue contact and geometric locations, especially in difficult areas such as around the papillary muscles. (Figure 5)
The Advisor HD Grid has revolutionized the art of multi-electrode mapping, providing us with information that we had not seen previously with standard multi-electrode mapping catheters. Use of the EnSite Precision system and intracardiac echo complements this technology well.
Disclosure: Dr. Siddiqui has no conflicts of interest to report regarding the content herein. Outside the submitted work, he reports grants from Abbott and Biosense Webster.
This article is published with support from Abbott.