Case Report: Utility of Frequency Mapping/Spectral Analysis in the EPLogix™ Mapping and Analysis Suite

Dominant Frequency (DF) mapping and AF cycle length (AFCL) monitoring software features are two of many features available on Bard’s LabSystem^™ PRO EP recording system in the new EPLogix^™ Mapping and Analysis Suite. The LabSystem PRO provides an integrated platform of cost-effective, simple to use tools for use in various arrhythmias, potentially saving the EP practitioner time and providing additional information useful in the evaluation of arrhythmias. Objective In this case report, it is hypothesized that spectral analysis and frequency mapping may be used to help localize an unusual anatomical focus that may be maintaining chronic atrial fibrillation (AF) and thus facilitate treatment. Background AF is an arrhythmia characterized by rapid and highly irregular atrial activity with a complex atrial activation sequence. Experimental evidence suggests that certain cases of AF are maintained by focal driving sources. Atrial activation mapping can be performed and atrial activation rate can be estimated as the frequency containing the maximum power in the frequency domain. Sites where high frequency activation is observed may serve as AF drivers. Frequency mapping to identify such AF drivers has been successfully used in humans with paroxysmal AF; however, for patients with permanent AF, its use and interpretation remains challenging. This report discusses the case of a patient with permanent AF in whom a high frequency site in the coronary sinus was uncovered by spectral analyzed DF mapping, which facilitated successful treatment of the patient’s arrhythmia. Case Presentation A 43-year-old man with a three-year history of permanent AF resistant to antiarrhythmic therapy and multiple electrical cardioversions was referred for treatment of AF. He had previously undergone three procedures for permanent AF and the following lesions had been performed: pulmonary vein isolation, linear lesions between the superior pulmonary veins (roof line) and between the mitral annulus and the left inferior pulmonary vein (mitral isthmus line). Relevant patient parameters include: • Number of failed AADs: 3 • Number of electrical cardioversions: 15 • Ejection fraction: 54% • LAD: 48mm • No structural heart disease  Electrical Mapping with EPLogix^™ Mapping and Analysis Suite Spectral-analyzed DF mapping using EPLogix^™ software (Bard Electrophysiology, MA) was performed during ongoing AF. The ElectroView^™ 3D Mapping algorithm was used to identify the location of the catheter tip on a 3D anatomic model, using the fluoroscopic image as a reference (Figure 1). The intracardiac electrograms were recorded on a computer-based digital amplifier/recorder system (LabSystem^™ PRO EP Recording System, Bard Electrophysiology) and were automatically recorded for each site. Signal Processing and Frequency Domain Analysis The signal processing and spectral analysis software utilized an automated, dedicated system. Thirty-second bipolar electrogram recordings were acquired at each point, with a programmable range between 5 and 30 seconds. The bipolar recordings were obtained on both mapping and coronary sinus catheters, and were then analyzed in the frequency domain with the Fast Fourier Transform on the LabSystem^™ PRO EP Recording System (Figure 2). The DF, the frequency with the maximal power, was chosen as an estimate of the local activation rate at each position, or more simply the ‘spectral signature’ of the underlying micro-circuit.  The regularity index (RI) and organization index (OI) were also captured at every point using the automated software. The RI is defined as the area within a 0.75Hz band around the DF divided by the area of the frequencies sampled between 3 and 30Hz. The OI is defined as the area within a 0.75Hz band around the DF and its harmonics divided by the area of the frequencies sampled between 3 and 30Hz. Both of these parameters are used to provide a measure of the consistency of the activation interval, and only points demonstrating both a RI > 0.2 and an OI > 0.25 were included for evaluation. In addition to frequency analysis, Bard’s EPLogix^™ Mapping and Analysis Suite offers additional advanced algorithms such as voltage mapping, local activation timing, and automated AFCL. These algorithms may be helpful in the assessment of arrhythmias such as AF, atrial flutters, and focal tachycardias. AFCL has recently been demonstrated to help characterize the complexity of an arrhythmia; gradual prolongation of the AFCL has consistently been observed to precede the termination of arrhythmia during the treatment of paroxysmal or permanent AF.² Mean AFCLs were determined by averaging 30 consecutive cycles using the EPLogix^™ software and by visual verification. The electrograms within the LAA were usually distinct and of high amplitude, thereby facilitating unambiguous automatic annotation. The process of assessing cycle length required < 60 seconds and was performed in review mode, allowing for quick and seamless use of the tools without disruption to the procedure flow.²Results A total of 15 points were recorded throughout the left atrium and coronary sinus (see Figure 5 for 3D Map and Figure 6 for subsequent analysis parameters). The highest DF site in the left atrium was located on the posterior wall with a DF equal to 6.35Hz. A frequency gradient of 2.84Hz was observed from the CS to the LA (mean value of DF in the LA: 5.80Hz). Furthermore, in this case the spectral analysis revealed the highest frequency activity on the distal and proximal recording poles of the coronary sinus mapping catheter (8.64 and 7.68Hz, respectively) with a good RI (0.39 and 0.24, respectively) and OI (0.45 and 0.28, respectively). The patient’s arrhythmia was treated inside the coronary sinus, and since then the patient has continued to be in sinus rhythm after a follow-up of four months. Conclusion This case illustrates the utility of identifying high frequency sources maintaining permanent AF by generating 3D DF maps using the EPLogix^™ Mapping and Analysis Suite. Spectral analyzed DF mapping of cardiac arrhythmias can reveal critical sites for the clinician’s consideration. It also demonstrates the ability of the EPLogix^™ Suite to highlight an unusual anatomical site that was maintaining an arrhythmia such as AF. This patient’s AF was well established (three years) and had proved to be resistant to treatment. The site of the AF focus was also unusual and would not be an obvious anatomical area to explore — the more common options being to re-map the pulmonary vein ostia and look for CFAE potentials on the posterior left atrial wall. By using the dominant frequency algorithm within the EPLogix^™ Suite, the physician was able to immediately identify the site of focal activation.  In addition, the value of having mapping and advanced analysis tools available on a high-fidelity recording system during complex procedures is highlighted here. The EPLogix^™ Mapping and Analysis Suite is available exclusively on Bard’s LabSystem^™ PRO EP Recording system with no additional costs or setup time. With the growing recognition of the role of electrogram-based therapeutic techniques, readily-available, integrated tools like this may be useful in clinical practice. Disclaimer: Bard Electrophysiology supported the creation and publication of this article. Bard Electrophysiology does not have any ablation catheters approved for treatment of AF in the United States; before use, consult product labels and inserts for any indications, contraindications, hazards, warnings, cautions and instructions for use. LabSystem, EPLogix, and ElectroView are trademarks of C. R. Bard, Inc. or an affiliate. © 2008 C. R. Bard, Inc. All rights reserved. LT04Z0242/Rev.0/05-2008 Disclosure: The authors have disclosed that one or more of them have a financial relationship with the company (Bard Electrophysiology) that produces or markets products or services relevant to the topic of this manuscript.