High-resolution Activation Mapping Research Articles

Biatrial flutters: unique circuits requiring a customized ablation approach

Abstract Introduction Atrial futters are macroreentrant tachycardias that typically involve several walls of a certain atrium, being the other atrium passively activated. Biatrial flutters (BAF) are peculiar macro-reentries associated with anterior/septal scars, involving both atria and using the interatrial connections. Purpose To characterize the mechanism of BAF a cohort of patients (pts) submitted to mapping and ablation. Methods Retrospective single-center study of pts with atypical atrial flutter submitted to ablation from 2015 to 2022. High resolution electroanatomical voltage and activation mapping were collected using Carto, Ensite or Rhythmia. Whenever the arrhythmia circuit was not fully displayed in a certain atrium, of the other atrium was mapped to fully characterize the reentrant circuit and establish the critical isthmus. Biatrial circuits were classified into 4 types: type 1, involving the mitral annulus and the tricuspid annulus, escaping the septal wall in both atria; type 2 using most of the mitral annulus and the right atrium (RA) septum; type 3, using both the left atrium (LA) and RA septum; and type 4, using most of the tricuspid annulus and the LA septum. Acute and long-term success was evaluated. Results From a total of 107 pts submitted to atypical flutter ablation, 5 pts presented BAF (3 male, median age: 55-yo), 4 of them previously submitted to cardiac surgery (CABG in 1, mitral valvuloplasty in 1, mitral+tricuspid valvuloplasty in 1 and surgical correction of aortic coarctation and ostium primum atrium septal defect in 1) and 1 had been previously submitted to pulmonary vein isolation (PVI), empirical roof line and cavotricuspid isthmus (CTI) ablation. A proximal-to-distal coronary sinus activation and extensive low-voltage areas at the septum were recognized in all these pts. The BAF mechanism was single loop in all of them, with a type 2 circuit in 2 pts, and types 1, 3 and 4 in one patient each. BAF types 1 and 4 were terminated with CTI ablation. BAF types 2 and 3 were terminated with linear ablations from the mitral annulus to the right superior PV, complemented with focal applications at Bachmann bundle insertion sites in the pts with type 2 BAF. Acute success was achieved in all pts. During a mean time of follow-up of 344±91 days, 1 pt had AFl recurrence. Conclusion BAF is a rare and complex arrhythmia, which is possible to ablate successfully by applying high-density mapping tools, a comprehensive analysis of the substrate/activation maps and a mechanism-tailored ablation strategy.

Abstract 18924: Structural and Electrical Remodeling Differences in Ischemia-Reperfusion versus Non-Reperfusion Myocardial Infarction

Background: Structural and electrical remodeling following myocardial infarction (MI) can result in the development of arrhythmogenic substrate and ventricular tachycardia (VT). Various clinical factors such as reperfusion status, and occluded coronary distribution can impact the size of post-infarction scar. Objective: To investigate the structural and electrical remodeling characteristics in 2 different porcine models of MI. Methods: Fourteen swine underwent anterior infarction via 180min balloon occlusion followed by reperfusion (IR Group, n=7) or chronic total occlusion by embolizing the mid-LAD with a coil (CTO Group, n=7). Cardiac MRI and electroanatomic substrate mapping (Thermocool ST-SF) and high-resolution activation mapping (Pentaray 2-6-2mm) was performed in all subjects 8-9 weeks following infarction. Low bipolar voltage area (<1.5mV), very low bipolar voltage area (<0.5mV), and CMR LGE intensity volume reconstruction (inHeart Medical) were assessed. Programmed stimulation from the Ventricular apex was performed for VT inducibility assessment. Results: The CTO group had more extensive low bipolar voltage area (CTO: 36±6cm 2 vs. IR: 23±12cm 2 , p=0.04) and dense low bipolar voltage areas (CTO: 20±7cm 2 vs. IR: 7±6cm 2 , p=0.01). LV EDV was similar (CTO: 122±14ml vs. IR: 136±38ml, np) and there was no significant difference in LVEF (CTO: 28±4% vs. IR: 26±4%, np) and CMR LGE scar volume (CTO: 12±3ml vs. IR: 12±4ml, np). Voltage mapping demonstrated clear significant differences in substrate size and LV Endocardial CMR LGE intensity was more homogeneous in the CTO group than the IR group (Figure). Monomorphic VT was inducible in all 14 subjects. A total of 19 VTs were induced in CTO group (range 1-4, TCL 241±33ms) and 12 in IR group (range 1-2, TCL 208±17ms). Conclusions: Creation of a chronic infarct results in a significantly larger area of abnormal arrhythmogenic substrate than 180 minutes of ischemia-reperfusion.

High-density electroanatomic activation mapping to guide slow pathway modification in patients with persistent left superior vena cava

Slow pathway (SP) mapping and modification can be challenging in patients with persistent left superior vena cava (PLSVC) due to anatomical variance of Koch's triangle (KT) and coronary sinus (CS) dilatation. There is a lack of studies using detailed 3-dimensional (3D) electro-anatomical mapping (EAM) to investigate conduction characteristics and guide ablation targets in this condition. To describe a novel technique of slow pathway mapping and ablation in sinus rhythm using 3D EAM in patients with PLSVC after validation in a cohort with normal coronary sinus anatomy. Seven patients with PLSVC and dual AV node physiology who underwent slow pathway modification with the use of 3D EAM were included. Twenty-one normal heart patients with AV nodal re-entrant tachycardias formed the validation group. High-resolution, ultra-high-density local activation timing (LAT) mapping of the right atrial septum and proximal coronary sinus in sinus rhythm was performed. SP ablation targets were consistently identified by an area in the right atrial septum with the latest activation time and multi-component atrial electrogram (EGM) adjacent to a region with isochronal crowding (deceleration zone). In PLSVC patients, these targets were located at or within 1 cm of the mid anterior CS ostium. Ablation in this area led to successful SP modification reaching standard clinical endpoints with a median of 43 sec of radio frequency energy or 14 mins of cryoablation without complications. High-resolution activation mapping of Koch's triangle in sinus rhythm can facilitate localisation and safe slow pathway ablation in patients with PLSVC.

Systematic Evaluation of High-Resolution Activation Mapping to Identify Residual Endocardial and Epicardial Conduction Across the Mitral Isthmus.

This study sought to systematically evaluate the ability of a high-resolution mapping system (Rhythmia, Boston Scientific, Marlborough, Massachusetts) to rapidly and accurately localize residual endocardial and epicardial conduction after mitral isthmus (MI) ablation, facilitating MI block. Achieving conduction block across the mitral isthmus (MI) is challenging. Fifty consecutive patients undergoing MI ablation after pulmonary vein isolation were enrolled. After initial endocardial radiofrequency (RF) ablation across the lateral MI, high-resolution activation mapping of the MI with simultaneous coronary sinus (CS) mapping was performed to verify block or localize residual conduction across the MI during left atrial (LA) appendage and CS pacing. Propagation maps were used to identify residual conduction across the MI as endocardial, via the CS or Marshall tract. In all 50 patients, after the initial endocardial ablation across the MI, repeat high-resolution mapping of the LA and CS was obtained (median: 3,329 mapped points; 4.0min of mapping time). The initial endocardial MI ablation resulted in block in 9 of 50 patients (18%). In the remaining 41 patients, the propagation map identified residual conduction in 4 patterns: 1) only endocardial gap in 12 patients (29%); 2) only CS connection in 10 patients (24%); 3) both endocardial and CS connections in 14 patients (34%); and 4) Marshall tract connection in 5 patients (12%). In 8 patients, the propagation map revealed residual conduction, despite differential atrial pacing suggesting bidirectional block. Focal ablation at the identified residual conduction site (median: 0.7min of RF) resulted in block in 49 of 50 (98%) patients. High-resolution propagation maps of the LA/CS rapidly and accurately localize residual endocardial and epicardial conduction across the MI. Focal ablation with short RF time at the identified gap(s) achieved complete block across MI in 98% of cases.

Use of high-density activation and voltage mapping in combination with entrainment to delineate gap-related atrial tachycardias post atrial fibrillation ablation.

An incomplete understanding of the mechanism of atrial tachycardia (AT) is a major determinant of ablation failure. We systematically evaluated the mechanisms of AT using ultra-high-resolution mapping in a large cohort of patients. We included 107 consecutive patients (mean age: 65.7 ± 9.2 years, males: 81 patients) with documented endocardial gap-related AT after left atrial ablation for persistent atrial fibrillation (AF). We analysed the mechanism of 134 AT (94 macro-re-entries and 40 localized re-entries) using high-resolution activation mapping in combination with high-density voltage and entrainment mapping. Voltage in the conducting channels may be extremely low, even <0.1 mV (0.14 ± 0.095 mV, 51 of 134 AT, 41%), and almost always <0.5 mV (0.03-0.5 mV, 133 of 134 AT, 99.3%). The use of multipolar Orion, HDGrid, and Pentaray catheters improved our accuracy in delineating ultra-low-voltage areas critical for maintenance of the circuit of endocardial gap-related AT. Conventional ablation catheters often do not detect any signal (noise level) even using adequate contact force, and only multipolar catheters of small electrodes and shorter interelectrode space can detect clear fractionated low-amplitude and high frequency signals, critical for re-entry maintenance. We performed a diagnosis in 112 out of 134 AT (83.6%) using only activation mapping and in 134 out of 134 AT (100%) using the combination of activation and entrainment mapping. High-resolution activation mapping in combination with high-density voltage and entrainment mapping is the ideal strategy to delineate the critical part of the circuit in endocardial gap-related re-entrant AT after AF ablation.

Safety and accuracy of the Rhythmia mapping system in pediatric patients

A new mapping system (Rhythmia) using a 64 mini-electrode small basket array (Orion) was developed that enables rapid high-density mapping in a short time. However, there are few reports about the usefulness of this system in pediatric cases. The purpose of this study was to investigate the safety and accuracy of the Rhythmia system and Orion catheter in children. Catheter ablation was performed using the Rhythmia system and Orion catheter in 23 patients younger than 20 years (body weight >20 kg) without a past medical history of cardiac disease. Mapping time, number of mapping beats, and number of mapping electrodes were compared for left atrium, right atrium and right ventricular outflow tract. Twenty-three maps of the right atrium were acquired in 12.6 minutes (range 8.9-15.1), consisting of 709 beats (range 492-1163) and 7132 electrograms (range 4618-10,533). Twelve maps of the left atrium were acquired in 12.1 minutes (range 9.8-14.6), consisting of 565 beats (range 446-881) and 6412 electrograms (range 4912-11,402). There were no significant difference in mapping time, accepted beats, and electrograms between the 2 chambers. Manual annotation was needed in 53 of 293,185 electrograms (0.01%) due to far-field ventricular electrogram sensing and artifact. No adverse events occurred in any of the cases. The Orion catheter and Rhythmia mapping system were safe and accurate for mapping various arrhythmias in pediatric patients. Detailed geometry and high-resolution activation mapping were acquired without the need for manual reannotation.

High-Resolution Mapping of Postinfarction Reentrant Ventricular Tachycardia: Electrophysiological Characterization of the Circuit.

In vivo description of ventricular tachycardia (VT) circuits is limited by insufficient spatiotemporal resolution. We used a novel high-resolution mapping technology to characterize the electrophysiological properties of the postinfarction reentrant VT circuit. In 15 swine, myocardial infarction was induced by left anterior descending artery balloon occlusion. Animals were studied 6 to 8 weeks after myocardial infarction. Activation mapping of VTs was performed by using the Rhythmia mapping system. Activation time was based on a combination of bipolar and unipolar electrograms. The response to overdrive pacing from different zones of the circuit was examined. A total of 56 monomorphic VTs were induced (3.8±2.1 per animal). Among these, 21 (37.5%) were hemodynamically stable and allowed mapping of the circuit. Isthmuses were 16.4±7.2 mm long and 7.4±2.8 mm wide. Conduction velocities were slowest at the inward curvature into the isthmus entrance (0.28±0.2 m/s), slightly faster at the outward curvature exit (0.40±0.3 m/s) and nearly normal at the central isthmus (0.62±0.2 m/s). In 3 animals, 2 VT morphologies with opposite axes sharing the same isthmus were mapped. Conduction velocities within the shared isthmus were dependent on the activation vector, consistently slower at the proximal curvature. Overdrive pacing from isthmus sites determined by activation mapping was consistent with entrainment criteria for isthmus. However, dimensions of the isthmus defined by entrainment exceeded dimensions of the isthmus measured by activation mapping by 32±18%. In postinfarction reentrant VT, conduction velocities are slowest at the proximal and distal curvatures. Entrainment mapping overestimates the true size of the isthmus. High-resolution activation mapping of VT may better guide ablation therapy.

Feasibility of a semi-automated method for cardiac conduction velocity analysis of high-resolution activation maps

Myocardial conduction velocity is important for the genesis of arrhythmias. In the normal heart, conduction is primarily dependent on fiber direction (anisotropy) and may be discontinuous at sites with tissue heterogeneities (trabeculated or fibrotic tissue). We present a semi-automated method for the accurate measurement of conduction velocity based on high-resolution activation mapping following central stimulation. The method was applied to activation maps created from myocardium from man, sheep and mouse with anisotropic and discontinuous conduction. Advantages of the presented method over existing methods are discussed.

A Century of Optocardiography

In the past decade, optical mapping provided crucial mechanistic insight into electromechanical function and the mechanism of ventricular fibrillation. Therefore, to date, optical mapping dominates experimental cardiac electrophysiology. The first cardiac measurements involving optics were done in the early 1900s using the fast cinematograph that later evolved into methods for high-resolution activation and repolarization mapping and stimulation of specific cardiac cell types. The field of "optocardiography," therefore, emerged as the use of light for recording or interfering with cardiac physiology. In this review, we discuss how optocardiography developed into the dominant research technique in experimental cardiology. Furthermore, we envision how optocardiographic methods can be used in clinical cardiology.

A17-6 Spontaneous onset of atrial fibrillation from the pulmonary vein musculature: High-resolution activation mapping with a basket catheter

A17-6 Spontaneous onset of atrial fibrillation from the pulmonary vein musculature: High-resolution activation mapping with a basket catheter

A17-6 Spontaneous onset of atrial fibrillation from the pulmonary vein musculature: High-resolution activation mapping with a basket catheter

A17-6 Spontaneous onset of atrial fibrillation from the pulmonary vein musculature: High-resolution activation mapping with a basket catheter

P2098 Spontaneous onset of atrial fibrillation from the pulmonary vein muscolature: high-resolution activation mapping with a basket catheter

P2098 Spontaneous onset of atrial fibrillation from the pulmonary vein muscolature: high-resolution activation mapping with a basket catheter