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In addition to pulmonary vein isolation, treatment of non–pulmonary vein foci is essential in the treatment of atrial fibrillation.
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Various mapping techniques for non–pulmonary vein foci have been reported, but they all require manual annotation and are dependent on the competence of the operator.
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By using the Intra-Cardiac Pattern Matching algorithm (CARTO 3; Biosense Webster, Diamond Bar, CA) and referencing from 2 locations, the right atrium and coronary sinus, it is possible to perform an automated mapping with higher differentiation accuracy.
Introduction
Radiofrequency catheter ablation has emerged as an important treatment modality for many cardiac arrhythmias.
2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design: a report of the Heart Rhythm Society (HRS) task force on catheter and surgical ablation of atrial fibrillation. Developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology (ESC) and the European Cardiac Arrhythmia Society (ECAS); and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). Endorsed by the governing bodies of the American College of Cardiology Foundation, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, the Asia Pacific Heart Rhythm Society, and the Heart Rhythm Society.
Pulmonary vein isolation (PVI) is now the standard treatment for paroxysmal atrial fibrillation (AF). Despite the best efforts to achieve long-term PVI, arrhythmia recurrence after catheter ablation is common. Several studies have found that non–pulmonary vein foci or excessive premature atrial complexes (PACs) are important in causing AF.
The use of a 3-dimensional anatomical mapping system to detect PAC origins by identifying the earliest activation site (EAS) relative to a fixed timing reference remains the most common strategy.
Manual mapping techniques can be time consuming, inaccurate, and difficult to reproduce.
Without operator intervention, Intra-Cardiac Pattern Matching software (CARTO 3; Biosense Webster, Diamond Bar, CA) automatically identifies changes in unipolar signals recorded by the coronary sinus (CS) reference catheter and assigns each pattern to its respective map based on the correlation score.
Normalized correlation is calculated for each channel with the reference waveform and the acquired arrhythmia based on the unipolar signal, and the correlation score is calculated based on the weighted sum of the calculated scores for each channel. This technique helps distinguish catheter-induced PACs from spontaneous or triggered PACs, which are the true cause of arrhythmia onset. However, because of a single-chamber reference, it has some limitations in distinguishing target PACs from other arrhythmia. A novel dual-pattern matching (DPM) technique could detect PACs more accurately without manual annotation because information from 2 axes is more accurate than information from 1 axis in determining spatial location.
Case report
A 69-year-old man was admitted to our facility with paroxysmal AF and desired a permanent cure via ablation. The patient had a history of hemorrhagic gastric ulcer. With a left atrial dimension of 41.0 mm, echocardiography revealed a normal left ventricular ejection fraction of 65%, normal valvular function, and no evidence of structural heart disease. His CHA2DS2-VASc and HAS-BLED scores were both 1. Catheter ablation was performed with an electroanatomical mapping system (CARTO 3; Biosense Webster) and an open-irrigated contact-force sensing catheter (ThermoCool SmartTouch ST-SF, Biosense Webster). Isoproterenol was injected after circumferential bilateral PVI, causing AF and frequent PACs (Figure 1).
Figure 1Intracardiac recordings show sinus rhythm (yellow arrow) and the earliest activation site of the non–pulmonary vein trigger (pink arrow) in the coronary sinus (CS) proximal location.
To use the DPM technique, a 6F 20-pole electrode catheter (EPstar RA-CS; Japan Lifeline, Tokyo, Japan) was inserted into the CS as a reference to map unipolar electrograms (EGMs) of triggered PACs from the CS and the right atrium (RA, Figure 2). The Intra-Cardiac Pattern Matching software was set with the score over 0.80, and a 15-mm circular mapping catheter (LASSO® NAV; Biosense Webster) was moved around the left atrium to detect the EAS of the triggered PACs.
Figure 2Representative examples of the dual Intra-Cardiac Pattern Matching algorithm (CARTO 3; Biosense Webster) distinguish sinus rhythm based on unipolar signals recorded by the reference catheter. A: The score of the clinical premature atrial complex (PAC) and sinus rhythm were 1.00 and 0.93 based on unipolar signals recorded by the coronary sinus (CS) catheter only. B: When unipolar electrograms recorded by CS and right atrium (RA) were used as the reference, the scores of the clinical PAC and sinus rhythm were 0.97 and 0.51, respectively. As a result, the electrograms from sinus rhythm were successfully eliminated from local activation time map.
The video depicts a real-world scenario in which sinus rhythm and the targeted PAC were correctly and automatically separated, and only the trigger PAC was acquired in the mapping (Supplemental Videos S1 and S2). In fact, the targeted PAC was successfully mapped in about 101 seconds (Figure 3). There were 57 PACs (28.8%) and 141 sinus beats (71.2%) detected. Forty-seven PACs (82.5%) were automatically distinguished and recorded for the local activation time map out of 57 beats, and the PAC was successfully eliminated by radiofrequency ablation. Isoproterenol was administered again after the ablation procedure, but PAC did not reappear, and no atrial tachyarrhythmias were induced.
Figure 3Local activation time (LAT) maps created with a single- and dual-reference techniques. A: LAT map created from unipolar signals from the coronary sinus (CS). The earliest activation site (EAS) was located in the left atrial septum that represents propagation from sinus rhythm. B: LAT map created from unipolar signals from the CS and right atrium (RA). The EAS was located in the left atrial inferior septum that represents propagation from clinical premature atrial complex only, excluding propagation from sinus node.
reported a self-reference mapping technique for detecting non–pulmonary vein foci without the use of a fixed reference catheter. However, the technique detects the EAS through manual annotation, which means that it is at the discretion of the operator and may not be reproducible. Furthermore, because there is no fixed reference, multiple sources and catheter-induced PACs cannot be distinguished. Another method is the vector mapping technique,
which is similar to our method, but when only the CS EGMs are used as a reference it may be difficult to distinguish focal sources propagating from the same direction. PACs are often difficult to distinguish solely based on P-wave morphology, and manual annotation varies by the operator according to their skill and experience level. In this case, the RA and CS EGMs of the targeted PAC were distinguished more accurately than the CS EGMs alone (Supplemental Figure S1). We confirmed that the PAC’s CS unipolar waveform could be used as a reference to distinguish sinus rhythm from the targeted PAC and discovered that the matching scores of the PAC and sinus rhythm were 1.00 and 0.93, which were quite similar (Figure 2A). When unipolar EGMs from the RA and CS were added to the reference, the PAC score was 0.97, and the sinus rhythm score was 0.51 (Figure 2B).
The first limitation concerns whether catheter-induced PACs can be properly excluded from the local activation time map using the DPM technique. Because the CARTO system is a contact mapping system, this should be possible. However, as demonstrated, the DPM technique can be used to automatically exclude nontargeted PACs with high accuracy. Second, no optimal cutoff value exists. The higher the cutoff value, the higher the positive predictive value, but it reduces the number of acquisition points for targeted arrhythmias and increases mapping time. Therefore, in actual clinical practice, a cutoff value of 0.80–0.85 is considered the most realistically versatile cutoff value.
Third, while this was a case of PAC from the left atrial septum, it is unclear whether the same mapping technique can be used for PACs from other sites (superior vena cava, crista terminalis, right atrial appendage, and left atrial appendage). Fourth, because the reference unipolar EGMs may be low voltage, automated morphology comparison may fail in patients with impaired atrial structure and function and unclear atrial potentials.
Acknowledgments
We are grateful to Kengo Sasaki for his assistance with electrophysiologic assessment and to Dr Derek J. Dosdall for editing the English language.
Written patient consent was received towards publishing this article.
Theoretical illustration of dual-chamber ICPM algorithm. The propagation of excitation from the sinus node and non-PV foci from the LA septum shows proximal-to-distal CS activation. However, when RA is added as a reference, excitation from the LA septum propagates to the HRA and LRA in the same phase, which is distinguishable from propagation from the sinus node. ICPM, Intra-Cardiac Pattern Matching; PV, pulmonary vein; LA, left atrium; PAC, premature atrial complex; CS, coronary sinus; RA, right atrium; HRA, high right atrium; LRA, low right atrium
Mapping to detect the earliest activation site using ICPM software with only CS electrograms
References
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2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design: a report of the Heart Rhythm Society (HRS) task force on catheter and surgical ablation of atrial fibrillation. Developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology (ESC) and the European Cardiac Arrhythmia Society (ECAS); and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). Endorsed by the governing bodies of the American College of Cardiology Foundation, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, the Asia Pacific Heart Rhythm Society, and the Heart Rhythm Society.
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