Ultra High-resolution Mapping System Research Articles

Guiding ablation strategies for ventricular tachycardia in patients with structural heart disease by analyzing links and conversion patterns of traceable abnormal late potential zone.

Substrate-based ablation can treat uninducible or hemodynamically instability scar-related ventricular tachycardia (VT). However, whether a correlation exists between the critical VT isthmus and late activation zone (LAZ) during sinus rhythm (SR) is unknown. To demonstrate the structural and functional properties of abnormal substrates and analyze the link between the VT circuit and abnormal activity during SR. Thirty-six patients with scar-related VT (age, 50.0 ± 13.7 years and 86.1% men) who underwent VT ablation were reviewed. The automatic rhythmia ultrahigh resolution mapping system was used for electroanatomic substrate mapping. The clinical characteristics and mapping findings, particularly the LAZ characteristics during SR and VT, were analyzed. To determine the association between the LAZ during the SR and VT circuits, the LAZ was defined as five activation patterns: entrance, exit, core, blind alley, and conduction barrier. Forty-five VTs were induced in 36 patients, 91.1% of which were monomorphic. The LAZ of all patients was mapped during the SR and VT circuits, and the consistency of the anatomical locations of the LAZ and VT circuits was analyzed. Using the ultrahigh resolution mapping system, interconversion patterns, including the bridge, T, puzzle, maze, and multilayer types, were identified. VT ablation enabled precise ablation of abnormal late potential conduction channels. Five interconversion patterns of the LAZ during the SR and VT circuits were summarized. These findings may help formulate more precise substrate-based ablation strategies for scar-related VT and shorter procedure times.

Delineation of an intra-isthmus reentry circuit around the coronary sinus ostium using an ultrahigh-resolution mapping system

Delineation of an intra-isthmus reentry circuit around the coronary sinus ostium using an ultrahigh-resolution mapping system

Evaluation of interatrial conduction pattern after pulmonary vein isolation using an ultrahigh-resolution electroanatomical mapping system.

Interatrial conduction consists of various muscular bundles, including the Bachmann bundle. In this study, we investigated interatrial activation patterns using ultrahigh-resolution left atrial endocardial mapping. This study investigated 58 patients who underwent catheter ablation of atrial arrhythmia via an ultrahigh-resolution mapping system (Rhythmia) at our hospital from May 2020 to January 2021. Left atrial voltage maps and activation maps were acquired after the ablation procedure during right atrial appendage (RAA) pacing. We defined left atrial breakout sites (LABSs) as centrifugal activation patterns shown by the LUMIPOINT Activation Search Tool. The distance between each LABS in the left atrial anterior wall and the superior border of the interatrial septum (DLABS-IAS) was measured on the shell of the electroanatomical map, and anterior LABSs were divided equally into roof- and septal-side groups. Fifty-three (91%) patients underwent cryoballoon pulmonary vein isolation. Ultrahigh-resolution left atrial mapping was successfully performed in all patients (6831 ± 2158 points). A total of 82 LABSs were identified in left atrial anterior wall; 34 patients had single LABS and 24 patients had dual LABSs. The mean DLABS-IAS was 10.3 ± 9.6mm. Seven patients also exhibited posterior LABS near the interatrial raphe below the right inferior pulmonary vein. Patients with a single roof-side LABS had significantly shorter left atrial activation times than those with a single septal-side LABS (81.6 ± 13.2ms vs. 93.5 ± 13.7ms, p < 0.05). Interatrial conduction patterns during RAA pacing varied between patients and affected the left atrial activation time.

Mapping and ablation of left atrial roof-dependent tachycardias using an ultra-high resolution mapping system

BackgroundLeft atrial roof-dependent tachycardias (LARTs) are common macroreentrant atrial tachycardias (ATs). We sought to characterize clinical LARTs using an ultra-high resolution mapping system.MethodsThis study included 22 consecutive LARTs in 21 patients who underwent AT mapping/ablation using Rhythmia systems.ResultsThree, 13, 4, and 2 LART patients were cardiac intervention naïve (Group-A), post-roof line ablation (Group-B), post-atrial fibrillation ablation without linear ablation (Group-C), and post-cardiac surgery (Group-D), respectively. The mean AT cycle length was 244 ± 43 ms. Coronary sinus activation was proximal-to-distal or distal-to-proximal in 16 (72.7%) ATs. The activation map revealed 13 (59.1%) clockwise and 9 (40.9%) counter-clockwise LARTs. A 12-lead synchronous isoelectric interval was observed in 10/19 (52.6%) LARTs. The slow conduction area was identified on the LA roof, anterior/septal wall, and posterior wall in 18, 6, and 2 ATs, respectively. Twenty concomitant ATs among 13 procedures were also eliminated, and peri-mitral AT coexisted in 7 of 9 non-group-B patients. In group-B, the conduction gap was predominantly located on the mid-roof. Sustained LARTs were terminated by a single application and linear ablation in 6 (27.3%) and 9 (40.9%), while converting to other ATs in 7 (31.8%) LARTs. Complete linear block was created without any complications in all, however, ablation at the mid-posterior wall was required to achieve block in 4 (18.2%) procedures. During 14.0 (6.5–28.5) months of follow-up, 17 (81.0%) and 19 (90.5%) patients were free from any atrial tachyarrhythmias after single and last procedures.ConclusionsThe LART mechanisms were distinct in individual patients, and elimination of all concomitant ATs was required for the management.

High Density 3D Mapping and Ablation of Complex Cardiac Arrhythmias: Our Experience in NICVD

Background: Catheter ablation can be curative in patients with drug-refractory tachyarrhythmias. 3D electro anatomical mapping (EAM) is an established tool facilitating catheter ablation. This system is particularly valuable for mapping complex arrhythmias, which provide excellent assistance to catheter navigation, reduces fluoroscopy exposure, and also allow for the accurate placement of catheters. The Rhythmia Mapping System (RMS, Boston Scientific) is a novel system that allows for ultra-fast, high-density 3D mapping. Aim of this Study: The aim of this study was to find out the result of a high-density 3D mapping for the ablation of complex Cardiac Arrhythmias and to share our experiences. Methods: A total number of 44 patients of different tachyarrhythmias were scheduled for catheter ablation by Rhythmia Mapping System in National Institute of Cardiovascular Diseases, Bangladesh from 3rd February’2018 to 18th July’2019. During and after, the procedure all the cases were evaluated for different procedure parameters, acute success and in-hospital success. Results: Among the patients (28/44 male) 13 (25.55%) cases were atrial fibrillation, 6 (16.64%) cases were atrial flutter, 6 (16.64%) cases were atrial tachycardia, 2 (4.55%) cases were ventricular tachycardia, 11 (25%) cases were PVC and 6 (16.64%) cases were accessory pathway. The mean age was 38±4.5 years. In 25 (56.82%) of tachyarrhythmia patients, the mechanism was macro reentry/micro reentry, while in 19 (43.18%) cases the mechanism was increased automaticity. In all cases, the tachycardias were adequately mapped &amp; proper identification of focus was done during the index procedure with the ultra-high density 3-D Rhythmia Mapping System (RMS). These all were successfully terminated by radiofrequency ablation, except one, which was one of the two cases of Ventricular tachycardia. With this system our study samples had a success rate of 98% with arrhythmia elimination. In patients of atrial fibrillation, all 4 pulmonary veins isolation were done. The mean mapping time was 28.6 ± 17 minutes, and the mean radiofrequency ablation time to arrhythmia termination was 3.2± 2.6 minutes. During our study only two out of 44 patients developed complications. One of the patients with atrial fibrillation developed cardiac tamponade and the other patient with PVC originating from Aortic cusp developed ischemic stroke. Fortunately, they were both managed accordingly. During hospital discharge, all the patients were free of tachyarrhythmia and were in sinus rhythm. Conclusions: This new automated ultrahigh-resolution mapping system allows accurate diagnosis of tachyarrhythmia circuits. Ablation of the focus resulted in high acute success. Bangladesh Heart Journal 2021; 36(2): 98-104

Ultra-high resolution mapping of reverse typical atrial flutter: electrophysiological properties of a right atrial posterior wall and interatrial septum activation pattern.

We aimed to elucidate the right atrial posterior wall (RAPW) and interatrial septum (IAS) conduction pattern during reverse typical atrial flutter (clockwise AFL: CW-AFL). This study included 30 patients who underwent catheter ablation of CW-AFL (n = 11) and counter-clockwise AFL (CCW-AFL; n = 19) using an ultra-high resolution mapping system. RAPW transverse conduction block was evaluated by the conduction pattern on propagation maps and double potentials separated by an isoelectric line. The degree of blockade was evaluated by the %blockade, which was calculated by the length of the blocked area divided by the RAPW length. IAS activation patterns were also investigated dependent on the propagation map. The average %blockade of the RAPW was significantly smaller in patients with CW-AFL than those with CCW-AFL (25 [3-74]% vs. 67 [57-75]%, p < 0.05). CW-AFL patients exhibited 3 different RAPW conduction patterns: (1) a complete blockade pattern (3 patients), (2) moderate (> 25% blockade) blockade pattern (2 patients), and (3) little (< 25% blockade) blockade pattern (6 patients). In contrast, the little blockade pattern was not observed in CCW-AFL patients. Of 11 CW-AFL patients, 4, including all patients with an RAPW complete blockade pattern, had an IAS activation from the wavefront from the anterior tricuspid annulus (TA), and 6 had an IAS activation from the wavefronts from both the anterior TA and RAPW. One patient had IAS activation dominantly from the wavefront from the RAPW. RAPW transverse conduction blockade during CW-AFL was less frequent than during CCW-AFL, which possibly caused various IAS activation patterns.

Ultrahigh resolution electroanatomical mapping of the transverse conduction of the right atrial posterior wall in cases with and without typical atrial flutter.

The right atrial posterior wall (RAPW) is known to form a conduction barrier during typical atrial flutter (AFL). We evaluated the transverse conduction properties of RAPW in patients with and without typical AFL using an ultrahigh resolution electroanatomical mapping system. This study included 41 patients who underwent catheter ablation of AF, typical or atypical AFL, in whom we performed RAPW mapping with an ultrahigh resolution mapping system during typical AFL and coronary sinus ostial pacing with three different pacing cycle lengths (PCLs) (1) PCL1: PCL within 40 ms of the AFL cycle length in patients with typical AFL or 250-300 ms for those without, (2) PCL2: 400 ms, (3) PCL3: PCL just faster than the sinus rate. Local RAPW conduction block was evaluated by propagation mapping and local double potentials separated by an isoelectric line. The functional block was defined as areas blocked during shorter PCLs but conductive during longer PCLs. The degree of blockade was calculated by dividing the blocked length by RAPW length(%blockade). Only two patients demonstrated a fixed complete RAPW block (100%, %blockade). Thirty-one patients demonstrated a partial block of RAPW, and the %blockade during PCL1-3 was 49.4 ± 19.8%, 39.5 ± 19.2%, and 35.0 ± 22.9% in this group, respectively. Functional block areas were frequently observed above the fixed block area adjacent to the RA-inferior vena cava junction. Transverse conduction block was more frequently observed in patients with typical AFL at any longitudinal level of RAPW. RAPW transverse conduction block is lower-side dominant and greater in patients with typical AFL than those without.

Mapping and ablation of clinical spontaneous perimitral atrial tachycardias using an ultra–high-resolution mapping system

Perimitral atrial tachycardias (PMATs) are common atrial tachycardias (ATs), yet their mechanisms vary. The purpose of this study was to characterize clinical spontaneous PMATs using an ultra-high-resolution (UHR) mapping system. The study included 32 consecutive PMATs in 31 patients who had undergone AT mapping/ablation using a UHR mapping system. Six, 10, 11, and 5 PMATs occurred in cardiac intervention-naïve (group A), post-lateral/posterior mitral isthmus linear ablation (group B), post-atrial fibrillation ablation without mitral isthmus linear ablation (group C), and post-cardiac surgery (group D) patients, respectively. Group A patients tended to be older, more likely were female, and had sinus node or atrioventricular conduction disturbances more frequently. A 12-lead synchronous isoelectric interval was observed in 15 PMATs (46.9%). Coronary sinus activation was proximal to distal or distal to proximal except in 3 PMATs with straight patterns due to epicardial gaps. Left atrial anterior/septal wall (LAASW) low-voltage areas were smallest in group B. Slow conduction areas (SCAs) were identified in 26 PMATs (81.2%) and were located on the LAASW in all group A and group D patients. Conduction velocity in the SCAs was slowest in group B. In group B, all PMATs were terminated by single applications, and the gaps were located epicardially in 5 of 10 (50%). Anterior (n = 23) or lateral/posterior (n = 9) mitral isthmus linear block was successfully created without any complications in all. Twenty-five concomitant ATs among 18 patients (58.1%) also were eliminated. During a median of 20.0 (11.0-40.0) months of follow-up, 28 patients (90.3%) were free from any atrial tachyarrhythmias. An UHR mapping-guided approach with identification of the individual tachycardia mechanism should be the preferred strategy given the distinct and complex arrhythmia mechanisms.

Chemical mapping as a predictor of vein of Marshall ethanol ablative effects.

The aim of this study was to test regional pharmacological effects of an antiarrhythmic agents to predict ablative effects. The vein of Marshall (VOM) providing vascular access to myocardial tissue has been used for ablative purposes using ethanol. A total of 35 patients (male 21, 63.2±7.8 years old) were included. A balloon-tipped infusion catheter was inserted into the VOM. Endocardial ultrahigh-resolution mapping was performed along the VOM region to record the change in atrial electrograms (AEs) after VOM injection of cibenzoline of 3.5mg during sustained atrial fibrillation (AF). Subsequently, ethanol was infused into the VOM and ablative region was mapped. In 17 patients (49 %), cibenzoline reduced AEs amplitude by>50%, all of which had also complete elimination of AEs following ethanol (Group A). In 18 patients (Group B), cibenzoline failed to eliminate AEs; yet, in 13 of 18 AEs were eliminated by ethanol. In the remaining five patients, ethanol did not eliminate AE. Cibenzoline into the VOM could reliably predicts the results of subsequent ethanol infusion into the VOM using ultrahigh-resolution mapping system, which leads to avoid unnecessary permanent lesion creation by ethanol infusion.

Characteristics of Marshall bundle-related atrial tachycardias using an ultrahigh-resolution mapping system.

Marshall bundle (MB)-related atrial tachycardias (ATs) have already been described; however, their characteristics using an ultrahigh-resolution mapping system are not yet well known. The purpose of this study was to clarify the characteristics of MB-related ATs with ultrahigh-resolution mapping. In 28 patients who underwent an electrophysiological study for ATs using an ultrahigh-resolution mapping system, precise circuits of 37 ATs were detected. Among those ATs, five were diagnosed as MB-related ATs that had epicardial connections among the reentrant circuits (mean age 76.6 ± 3.7years, one male patient). We analyzed the characteristics of those MB-related ATs with ultrahigh-resolution mapping. The mean cycle length was 260 ± 60ms, and the total acquired electrograms were 12,962 ± 2616 points. Two ATs were perimitral ATs, two rotated around the left pulmonary vein (PV), and one rotated around the left inferior PV. All ATs had a centrifugal activation pattern: 5 o'clock on the mitral annulus in four ATs and the upper ridge in one. Tiny potentials, which indicated epicardial potentials covering the cycle length, were detected in four of five ATs. The local activation times covered over 95% of the tachycardia cycle length on the endocardial side only in all ATs. All ATs were terminated during a radiofrequency ablation from the endocardial side of the Marshall bundle. The ultrahigh-resolution mapping system demonstrated an activation map of MB-related ATs with a centrifugal pattern. Macroreentrant tachycardias with a centrifugal activation pattern should be considered as possible MB-related ATs.

Centrifugal wave-front propagation speed for localizing the atrial tachycardia origin

BackgroundThe earliest activation site (EAS) on a centrifugally-propagated atrial tachycardia (AT) map may represent the true AT origin (true-focal pattern), or the earliest site resulting from passive activation of AT originating from neighboring tissue (pseudo-focal pattern). We assessed the benefits of using the wave-front propagation speed to distinguish between the true- and the pseudo-focal pattern. MethodsAT mapping was performed using a novel ultra-high resolution mapping system with a 64-electrode mini-basket catheter. The true AT origin was defined as the site where radiofrequency application eliminated AT. The wave-front propagation speed was estimated from the area surrounded by the centrifugally-propagated wave front over a specific time interval. ResultsTotal of 46 centrifugally propagated AT maps from 34 patients were analyzed, including 18 true-focal and 28 pseudo-focal pattern. The area surrounded by the propagated wave front was significantly smaller for the true-focal pattern than for the pseudo-focal pattern, 1–20 msec after the earliest activation. The true-focal pattern was identified by the area 13 msec after the earliest activation, with the best cut-off area value of <4.5 cm2. ConclusionThe presence or absence of a true origin of AT at the EAS on centrifugally-propagated AT maps can be distinguished using a wave-front propagation speed.

P938A case of single loop bi-atrial macro-reentrant tachycardia: the diagnostic support of ultra high resolution mapping system

P938A case of single loop bi-atrial macro-reentrant tachycardia: the diagnostic support of ultra high resolution mapping system

Characteristics of Single-Loop Macroreentrant Biatrial Tachycardia Diagnosed by Ultrahigh-Resolution Mapping System.

Biatrial tachycardia (BiAT) is a rare form of atrial macroreentrant tachycardia, in which both atria form a critical part of the circuit. We aimed to identify the characteristics and precise circuits of single-loop macroreentrant BiATs. We identified 8 patients (median age, 59.5 years old) with 9 BiATs in a cohort of 336 consecutive patients from 2 institutions who had undergone AT catheter ablation using an automatic ultrahigh-resolution mapping system. Seven of the 8 patients had a history of persistent AF ablation, including septal or anterior left atrium ablation before developing BiAT. One of the 8 patients had a history of an atrial septal patch closure with a massively enlarged right atrium. Nine ATs (median cycle length, 334 ms; median 12 561 points in the left atrium; 8814 points in the right atrium) were diagnosed as single-loop macroreentrant BiATs. We observed 3 types of BiAT (1) BiAT with a perimitral and peritricuspid reentrant circuit (n=3), (2) BiAT using the right atrium septum and a perimitral circuit (n=3), and (3) BiAT using only the left atrium and right atrium septum (n=3). Catheter ablation successfully terminated 8 of the 9 BiATs. All patients who developed BiAT had an electric obstacle on the anteroseptal left atrium, primarily from prior ablation lesions. In this situation, mapping of both atria should be considered during AT. Because 3 types of single-loop BiAT were observed, ablation strategies should be adjusted to the type of BiAT circuit.

The identification of conduction gaps after pulmonary vein isolation using a new electroanatomic mapping system

The reconnection of left atrial-pulmonary vein (LA-PV) conduction after the initial procedure of pulmonary vein (PV) isolation is not rare, and is one of the main cause of atrial fibrillation (AF) recurrence after PV isolation. We investigated feasibility of a new ultrahigh-resolution mapping system using a 64-pole small basket catheter for the identification of LA-PV conduction gaps. This prospective study included 31 consecutive patients (20 with persistent AF) undergoing a second ablation after a PV isolation procedure with LA-PV reconnected conduction at any of the 4 PVs. An LA-PV map was created using the mapping system, and ablation was performed at the estimated gap location. The propagation map identified 54 gaps from 39 ipsilateral PV pairs, requiring manual electrogram reannotation for 23 gaps (43%). Gaps at the anterior and carinal regions of left and right ipsilateral PVs required manual electrogram reannotation more frequently than the other regions. The voltage map could identify the gap only in 19 instances (35%). Electrophysiological properties of the gaps (multiple gaps in the same ipsilateral PVs, conduction time, velocity, width, and length) did not differ between those needing and not needing manual electrogram reannotation. During the gap ablation, either the activation sequence alteration or elimination of PV potentials was observed using a circular catheter placed in the PV, suggesting that all the identified gaps were correct. This new electroanatomic mapping system visualized all the LA-PV gaps in patients undergoing a second AF ablation.

299 - A new automated ultra-high resolution mapping system allows detection of very low voltage critical signals in scarred human atria

299 - A new automated ultra-high resolution mapping system allows detection of very low voltage critical signals in scarred human atria

Selection of Critical Isthmus in Scar-Related Atrial Tachycardia Using a New Automated Ultrahigh Resolution Mapping System.

Accurate activation mapping of reentrant scar-related atrial tachycardias (AT) allows efficient radiofrequency ablation by targeting the critical isthmus (CI). We aimed to assess the electrophysiological properties of CI channels during mapping with the IntellaMap Orion basket and the Rhythmia system. We prospectively studied 33 AT (post- atrial fibrillation ablation or surgical mitral valve repair). The noise of bipolar electrogram (EGM) was systematically measured at 10 prespecified sites, as well as on a standard catheter and on the surface ECG. Bipolar EGM of CI regions were analyzed for amplitude, duration, and conduction velocity. The isthmus region to be targeted was chosen based solely on propagation. For each AT, 25 684±14 276 EGMs were automatically annotated. Noise of the Orion EGM was 0.011±0.004 mV, lower than that of a standard catheter (0.016±0.019) and surface ECG (0.02±0.01; P<0.05). For reentrant AT, within the CI, bipolar EGM amplitude (0.08±0.11 mV) and conduction velocity (0.27±0.19 m/s) were lower than those orthodromically before (0.62±0.93 mV; 1±0.49 m/s) and after (0.80±1.59 mV; 1±0.73 m/s) the isthmus (P<0.001 for all). In 97% of AT, ablation at the CI resulted in AT termination. No complications occurred. This new automated ultrahigh resolution mapping system produces low noise and allows accurate diagnosis of AT circuits. CI on reentrant scar-related AT showed much lower EGM amplitude with a significantly slower conduction velocity than the surrounding parts of the circuit. Ablation of the areas of slow conduction resulted in a high acute success.

16-23: Endocardial voltage mapping of pulmonary veins with a new ultra high-resolution electroanatomical mapping system to evaluate atrial myocardial extensions

16-23: Endocardial voltage mapping of pulmonary veins with a new ultra high-resolution electroanatomical mapping system to evaluate atrial myocardial extensions

96-21: Detection of Very Low Voltage Critical Signals In Scarred Human Atria with A New Automated Ultra-high Resolution Mapping System

Purpose: Critical areas of arrhythmogenesis occur mostly in diseased tissue where voltage is attenuated often below the background noise (BGN). A new 64-poles basket mapping system catheter incorporates very small unidirectional electrodes (0.4 mm2; 2.5 mm center to center interelectrode spacing). We measured BGN on the bipolar electrograms (Eg) channels during mapping of scar-related atrial (A) tachycardias (T) and compared it to Eg in the critical AT isthmus. Method: Patients (n = 16, 69 ± 8 y) with scar-related AT (n = 22) were prospectively studied. Of these, 73% occurred after atrial fibrillation ablation and 27% after a surgical mitral valve repair (adjunct maze in 23%). Both A were mapped for each AT. BGN was measured at pre-specified sites: left A: mid-roof, mid-posterior wall, posterior mitral annulus, inter-A septum, mid-anterior wall, appendage; right A: cavo-tricuspid isthmus, septum, appendage and crista terminalis; see figure) for each map. BGN was also assessed on standard decapolar catheter (2 mm ring electrodes and spacing) and on surface ECG. Scar thresholding was performed whenever necessary in order to visualise the entire circuit. The amplitude of the smallest bipolar Eg of the “isthmus” of macroreentrant AT (targeted for ablation) was also measured. Summary of results: Mean BGN of basket Eg was 0.011 ± 0.003 mV (see figure for each site), lower than the decapolar catheter (0.019 ± 0.023) and surface ECG (0.032 ± 0.023; p < 0.0001). Scar threshold was established at 0.016 ± 0.010 mV (median 0.015). Bipolar Eg amplitude within the critical isthmus was 0.1 ± 0.1 mV. In 9 cases (41%), isthmus bipolar Eg was <0.05 mV and in 6 cases <0.03 mV, but above the adapted scar threshold.

Insights from preclinical ultra high-density electroanatomical sinus node mapping

Although sinus node modification by catheter ablation is an established therapy for the treatment of inappropriate sinus tachycardia, there is incomplete understanding of sinus node anatomy and function but also limited electroanatomical mapping data. Recently, an automatic, ultra high-resolution mapping system has been presented to accurately and quickly identify right atrial (RA) geometry and activation patterns but detailed assessment of sinus node activation has not been performed which was one aim of this study. Preclinical experiences are compared with previous sinus node mapping studies in animals and humans, and potential clinical implications for catheter ablation are discussed. In anaesthetized and ventilated 14 pigs, 30 endocardial and 2 eipcardial RA maps were generated using the Rhythmia™ mapping system without complications and earliest activation sites (EAS) and sinus break-out (SBO) were determined. At baseline, EAS and SBO were located anterior to the middle (n = 6) or lower third (n = 8) of the crista terminalis exhibiting a unicentric activation pattern in all cases. Conduction pathways were directed anterior, posterior, superior, or inferior with substantial inter-individual variation in direction, pathway distance, and conduction time. Orciprenaline, propranolol, or amiodarone shifted endocardial activation with considerable variation between animals with inconsistent patterns. Multicentric activation was found in one case after orciprenaline infusion. Sequential endocardial and epicardial high-density mapping of the RA was performed in two animals and showed a high congruence of the sinus node activation in the endo- and the epicardial map. Ultra high-density mapping allows fast, simple, and very detailed assessment of sinus node activation. Future studies are clearly needed to evaluate novel mapping and ablation strategies for an improved understanding of sinus node disease and better outcomes.