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Catheter ablation of atrial and ventricular arrhythmias is now considered a standard technology for selected patients. In some patients, however, cure of the arrhythmia is hampered by the complexity of the arrhythmia or the way the arrhythmia presents in the electrophysiological laboratory: some focal atrial and ventricular arrhythmias are difficult to induce using electrical stimulation or medical provocation. Precise mapping of these arrhythmias is challenging or even impossible by contact mapping, while other arrhythmias are poorly tolerated and need early termination. In these scenarios, use of non-contact mapping technology can be an alternative to conventional mapping, since isopotential maps may require no more than one ectopic beat identical with the clinical focal arrhythmia to reconstruct its endocardial origin. This review article presents the technology of non-contact cardiac mapping, as well as various arrhythmias that have been successfully treated using this technology in the past. The possibilities and limitations of using non-contact cardiac mapping under various conditions are also presented.

Background Global simultaneous recording of activation during atrial fibrillation (AF) can elucidate underlying mechanisms contributing to AF maintenance. A better understanding of these mechanisms may allow for a personalised ablation strategy to treat persistent AF. Purpose To characterise left atrial endocardial activation patterns during AF using a novel non-contact dipole density mapping. Methods Activation patterns were characterised into three sub-types: (i) focal with centrifugal activation (FCA); (ii) localised rotational activation (LRA); (iii) localised irregular activation (LIA). Continuous activation patterns were quantified and distributed in the left atrium. Results A total of 144 persistent AF segments with 1068 activation patterns from 25 patients were analysed. The most common pattern was LIA (63%), which consist of four disparate features: slow conduction (45%), pivoting (30%), collision (16%) and acceleration (7%). LRA was the second commonest pattern (20%). FCA (17%) arose frequently from the PVs/ostia. Continuous AF activations comprise multiple combinations of FCA, LRA and LIA, transitioning from one to the next without a discernible order. Preferential conduction areas were typically seen in mid-anterior (48%) and lower-posterior (40%) walls where dominant activations were made up of LRA and LIA. Conclusion AF is characterised by heterogenous activation patterns that vary between individuals. Clinical implications of individualised ablation strategies guided by dipole density mapping will have to be determined. Acknowledgement/Funding None

This study investigates the fatigue performance of corroded bridge wires by providing characterisation of the corrosion effects through non-contact surface mapping and by undertaking fatigue tests under constant amplitude loading. For the corrosion level investigated, the breakage position in corroded wires was found to be better correlated with maximum area loss rather than pit depth. Using also test results for un-corroded wires, S-N relationships were determined for both that set and the corroded wire set created in this study. The effect of corrosion was quantified through the estimation of the coefficients for both the mean and the design S-N curves.

Catheter ablation is a widely-used therapy to treat atrial fibrillation (AF), but the identification of ablation targets remain challenging in persistent AF (persAF). Dominant frequency (DF) mapping has been shown to be spatiotemporally unstable in persAF, with DF variability (DFV) correlating with the spectral organisation index (OI). This study aims to assess DFV at ablation sites between patients with AF termination and non-termination. 10 persAF patients undergoing LA ablation were enrolled. AF was terminated in 4 patients after ablating highest DFs. 2048-channel virtual electrograms (Ensite Array) were analysed in Matlab. DFV index (DFVI) was proposed to quantify DF temporal stability. Mock ablation targets were identified based on DFVI and the percentage of region actually ablated was computed. Ablation sites in termination patients revealed higher OI and lower DFVI. In the termination group, a greater proportion of DFVI was ablated. Atrial regions with higher temporal stability and organisation may offer more precise locations of stable focal drivers and may lead to higher success in AF termination following ablation.

Aims To identify unique electrophysiological characteristics of pulmonary artery (PA) ventricular arrhythmias (VA) and determine long-term clinical outcomes following non-contact mapping (NCM)-guided ablation. Methods and results The NCM array was deployed in consecutive patients undergoing clinically indicated ablation of outflow tract (OT) VA with left bundle branch block morphology, inferior axis and the precordial lead transition zone ≥V3. Activation, pace and NCM mapping parameters, and electrocardiogram analysis of PA VA patients were compared with 50 patients with right ventricular OT (RVOT) or aortic coronary cusps (ACC) foci. Of 170 consecutive patients, 20 (12%) patients (8 male, 39.7 ± 12.8 years old) with PA VA were identified. Electrocardiogram morphologies of PA ventricular tachycardia (VT) (located 10.8 ± 15.1 mm above the PV) were indistinguishable from RVOT VT, particularly those arising from the septal RVOT. Pulmonary artery VT can be mapped and ablated by targeting the site of earliest activation on NCM maps, with success rates of 90% after a single procedure, without anti-arrhythmics and mean follow-up of >5 years. Pace-mapping in the PA is complicated by frequent inability to capture ( P < 0.01). Small far-field atrial potentials and smaller ventricular electrograms were more frequently recorded at successful sites of ablation in the PA ( P < 0.05). Conclusion Non-contact mapping is a useful technique to map PA VT and ablation at sites of earliest activation above the pulmonary valve is associated with excellent long-term clinical success.

Since the discovery of the role of the pulmonary veins (PVs) in the initiating process of atrial fibrillation (AF), it has been known that a minority of ectopic beats initiating AF arise from non-PV regions. The elimination of such non-PV foci is critical for the maintenance of sinus rhythm. Although provocation maneuvers provide us with the opportunity to map non-PV foci, mapping of non-PV foci is challenging, particularly in cases with an immediate occurrence of AF. Knowledge about the prevalence of non-PV foci, the P-wave morphology, and the use of new mapping technologies is helpful in identifying non-PV foci. As for foci in the left atrial appendage or persistent left superior vena cava, electrical isolation of those structures successfully eliminates the triggers without any precise localization of the foci.

ECG imaging is an emerging technology for the reconstruction of cardiac electric activity from non-invasively measured body surface potential maps. In this case report, we present the first evaluation of transmurally imaged activation times against endocardially reconstructed isochrones for a case of sustained monomorphic ventricular tachycardia (VT). Computer models of the thorax and whole heart were produced from MR images. A recently published approach was applied to facilitate electrode localization in the catheter laboratory, which allows for the acquisition of body surface potential maps while performing non-contact mapping for the reconstruction of local activation times. ECG imaging was then realized using Tikhonov regularization with spatio-temporal smoothing as proposed by Huiskamp and Greensite and further with the spline-based approach by Erem et al. Activation times were computed from transmurally reconstructed transmembrane voltages. The results showed good qualitative agreement between the non-invasively and invasively reconstructed activation times. Also, low amplitudes in the imaged transmembrane voltages were found to correlate with volumes of scar and grey zone in delayed gadolinium enhancement cardiac MR. The study underlines the ability of ECG imaging to produce activation times of ventricular electric activity-and to represent effects of scar tissue in the imaged transmembrane voltages.

Introduction: We investigated electrophysiological properties of the entire right ventricular (RV) endocardium of provoked ventricular tachycardia/ventricular fibrillation (VT/VF) in 2 patients with Brugada syndrome (BS). Methods: N/A. Results: Case 1. Type 3 Brugada type ECG which changed to type 1 ECG by class Ic antiarrhythmic drug, pilsicainide. Electrophysiologic study (EPS): Double ventricular premature stimuli from RVOT (600/260/200 ms) induced VF. The multielectrode array (Ensite, St. Jude Medical) was placed at the right ventricular outflow tract (RVO) and VF was induced again from RVOT (600/224/180 ms). Non-contact mapping during organized rapid VT before degenerating into VF showed that provoked VT arose from RVOT. Case 2: Type 1 Brugada type ECG. EPS: Triple ventricular premature stimuli from RV apex (600/250/220/200 ms) reproducibly induced VF. Non-contact mapping during organized rapid VT showed that provoked VT arose from RV free wall. Conclusion: RVOT and RV free wall appears to be crucial in the initiation and maintenance of VT with degeneration into VF in BS.

Ventricular outflow tract arrhythmias (VOTAs) can be successfully treated by catheter ablation. However, it is sometimes difficult to differentiate the origin of VOTAs between the right ventricular outflow tract (RVOT) and the other sites, leading to a long fluoroscopy time and unnecessary radiofrequency applications. This study aimed to clarify distinguishable characteristics of the propagation pattern obtained from non-contact mapping (NCM) for VOTA ablation. Consecutive 45 patients with VOTAs who underwent catheter ablation using the NCM system were included in this study. We analyzed an isopotential map on three-dimensional geometry of the RVOT obtained from the virtual unipolar electrograms (VUEs) and assessed mapping data of the isopotential area with an initial negative VUE of −1 mV. Successful ablation was achieved from the endocardial RVOT in 34 patients (RVOT group) and the non-RVOT in 11 (non-RVOT group). Major and minor axis diameters of the isopotential area did not significantly differ between the two groups. However, a ratio of major/minor axis diameter was greater in the RVOT group (1.9 ± 0.1 versus 1.3 ± 0.1; P

Background The relative importance of focal drivers, multiple wavelets, rotors and endocardial–epicardial circuits in the maintenance of persistent AF remains unclear. Our objective was to characterize AF wavefront (WF) dynamics during persistent AF. Methods The Ensite 3000 (St Jude Medical) non-contact mapping system was used to map the LA of 15 patients with persistent AF. Wavefronts were classified into planar WFs, rotors or focal WFs. For each new WF the site of origin, the unipolar electrogram, and propagation patterns were determined. Results AF was characterized by highly unstable patterns of activation with random combinations of 1–2 propagating planar wavefronts alternating with focal activations in a dynamic process. Stable reentry circuits and rotors were never seen. A total of 499 wavefront patterns were analyzed in this study (416 planar wavefronts and 83 focal wavefronts). In an individual patient planar WFs accounted for 67±35% of activations with lifespans of 98±86ms. Focal activations accounted for 29.7±33.5% of activations with lifespans of 76±95ms. The most common sites for new WF generation were the PVs (33%), LA roof (23%), anterior LA (15%), LAA (11%), and posterior LA (8%). The most common unipolar electrogram morphologies observed were QS pattern (34%), rS (29%), CFAE (26%), QR (7%) and Rs (4%), suggesting that WFs may originate from both the endocardial and epicardial surfaces. Conclusion Human persistent AF is characterized by the formation of highly unstable WFs consisting of various combinations of one to two planar WFs and brief focal activations without any evidence of rotors or sustained focal sources.

We report our local experience in using the non contact mapping system in guiding catheter ablation of unstable/non sustained Ventricular tachycardia (VT) and its short and long term implications. Patients and methods This report includes 18 cardiomyopathic patients, 13 males, age 40.5 ± 15 yrs, who presented to our centre with VT that share in common being unstable or non sustained. The patients were subjected to radiofrequency catheter ablation guided by the non contact mapping system. Results Acute successful outcome was obtained in 6 out of 8 (75%) patients with scar related VTs (post myocardial infarction and arrhythmogenic right ventricular dysplasia) and 9 of 10 (90%) patients with idiopathic dilated cardiomyopathy. Long term follow up for 6–24 (16 ± 8) months showed recurrence in one case of the scar related group and in two cases of the idiopathic group, so the overall long term success rates were 62.5% vs 70% (P. NS). Regular Echocardiographic showed an improvement of 10–15% in the Ejection Fraction in successful cases of the idiopathic group (Average Post-ablation EF in the idiopathic group of 49 ± 5% vs pre-ablation EF of 41 ± 4% while 42 ± 6 pre Vs 42 ± 7% post ablation in the scar related group) (P Conclusion Non contact mapping guided RF ablation of unstable VT in patients with cardiomyopathy showed good immediate results and long term outcome both in scar related and in idiopathic cardiomyopathy patients. Successful RF ablation of non sustained ventricular dysrhythmias among patients with idiopathic Cardiomyopathy may improve LV dysfunction.

We present a new approach for the reconstruction of ischemic regions from only a few non-contact intracardiac recordings. Hence, it is desirable to exploit the spatio-temporal correlations contained in the data. To this end, we incorporate a time-dependent monodomain model of the cardiac electric activity into the inversion scheme. In order to take into account the electrophysiological alterations of ischemic regions, we also introduce appropriate variations of the model parameters. This approach allows us to perform the reconstruction of the affected regions successfully using only a few recording sites. The reconstruction process is based on level set techniques. Our numerical experiments in a bi-dimensional model of cardiac tissue validate our approach.

Objectives The present study evaluated the clinical benefits of a new therapeutic method of radiofrequency catheter ablation (RFCA) using an EnSite system for inappropriate sinus tachycardia (IST). Materials and Methods Six patients with debilitating IST underwent RFCA using EnSite. Using the beta-adrenergic blocker and agonist, the heart rate was controlled between 70 to 150 bpm before and after the RFCA. The areas of the breakout sites (BOSs) were clearly distinguished between those from the normal P-wave zones during rates of less than 100 bpm and those from more upper rate sites during rates of more than 100 bpm using the EnSite system, in accordance with the appearance of tall P-waves (tall P-wave zone) in the IST patients. This was selected as the target for ablation. Results After the RFCA, the BOSs observed during heart rates of more than 100 bpm moved completely from the tall P-wave zone to the normal P-wave zone in the IST patients. The total number of heart beats and average heart beat on the 24-h Holter monitoring decreased statistically from that before the RFCA to that after, and no adverse heart rate responses was observed after the RFCA. Before the RFCA, the brain natriuretic peptide was elevated, New York Heart Association functional class was worse, and there was an impaired exercise tolerance observed with exercise electrocardiogram testing. The RFCA for the IST significantly improved those parameters. Conclusion This new therapeutic method for IST using EnSite is effective and produces clinical benefits.

Aims Ablation of right-sided accessory pathways (APs) is sometimes challenging because several anatomical features of the tricuspid annulus (TA) and surrounding structures differ from those of the mitral annulus. This study investigated the electrophysiological characteristics and efficacy of a non-contact mapping (NCM) system for catheter ablation of right-sided APs. Methods and results We examined nine APs in six consecutive patients who underwent catheter ablation of right-sided APs with NCM. In Case 6, we compared NCM with contact activation mapping. Three of six patients had two APs, and one of these had previously failed ablation. We observed atrial activation during sinus rhythm or atrial pacing using a multiple-electrode array (MEA) deployed in the right atrium near the TA. Non-contact mapping identified the AP location as a peri-TA breakout point that appeared prior to or simultaneously with the delta wave onset in all APs. In Case 6 we confirmed that the peri-TA breakout identified by NCM corresponded to the earliest ventricular activation identified by contact mapping. We successfully ablated nine APs by radiofrequency (RF) energy application to the breakout sites, while one AP located just above the pole of the MEA required additional conventionally guided mapping and ablation. The mean RF duration was 189.8 ± 119.0 s. After 33.2 ± 9.4 months of follow-up, one para-hisian AP and one right lateral AP recurred, but these were successfully ablated in a second procedure using NCM. Conclusion Non-contact mapping was able to identify the location of right-sided APs accurately and quickly.

A B S T R A C T Premature ventricular contractions originating in the right ventricular outflow tract may respond poorly to pharmacological treatment, and ablation using conventional fluoroscopically-guided systems may be complicated by the difficulty in inducing arrhythmias. We describe the use of a non-contact mapping system to ablate difficult-to-induce premature ventricular contractions originating in the right ventricular outflow tract. Five premature ventricular contractions sites in the right ventricular outflow tract were ablated in a prospective series of 4 patients. Patients had a poor quality of life and had not responded to antiarrhythmic drugs. A mean of 3 radiofrequency pulses per site was applied and mean application time was 113 � 15 s. We achieved a 100% acute success rate and there were no complications. Patients were asymptomatic without drug therapy after a mean of 30 � 16 months of follow-up. The noncontact mapping system is highly effective in eliminating difficult to induce, isolated premature ventricular contractions.

Back ground: Three-dimensional mapping systems such as the non-contact mapping system (EnSite) have been utilized for radiofrequency catheter ablation (RFCA) in cases with various kinds of arrhythmias. Methods: An EnSite system was utilized for RFCA in 12 patients with right-sided atrial tachycardia (AT). The patients were classified into two groups according to the focus of the AT in the right atrium (RA). The patients in whom the EnSite array was positioned near the focus of the AT were defined as group A, whereas those patients in whom the EnSite array was located less near the focus were defined as group B. RF energy was applied under the guidance of the mapping with the EnSite array. We investigated the relationship between the position of the EnSite array and the focus of the AT in terms of the mapping accuracy in both groups. Results: Even though the accuracy of the mapping of the breakout site and arrhythmia origin was comparable between groups A and B, the distance between the successful CA sites and the presumed AT focus according to the EnSite mapping was significantly shorter in group A than group B. Conclusions: As the location of the focus of the AT becomes closer to the proximal and distal ends of the ESB, the mapping accuracy deteriorates.

Right ventricular (RV) pacing has been associated with abnormal cardiac electrical and mechanical dyssynchrony, resulting in impaired global and regional ventricular pump function. This study aimed to characterize the relative effects of pacing site on left ventricular (LV) activation patterns and associated hemodynamic performances. Acute pacing was performed in anesthetized swine (n = 10) instrumented for RV and LV pressure, non-contact mapping (NCM) of endocardial unipolar electrograms, surface ECG, aortic flow, and sonomicrometry. Bipolar endocardial pacing leads were positioned in the right atrial appendage (RAA), RV apex (RVA), and RV outflow tract (RVOT), while bipolar epicardial leads were positioned on the LV-free wall (LVFW) and LV apex (LVA). LVFW and RVA pacing induced the largest increase in intraventricular electrical dyssynchrony (IVED; 32.2 ± 10 ms, 21.7 ± 4.1 ms, respectively; both p

The treatment of ventricular tachycardia (VT) in patients with underlying ischaemic heart disease (IHD) remains a challenge. Ablation of these arrhythmias may have a significant impact on quality of life for patients. For those patients with haemodynamically unstable VT, ablation success rates have been improved by the use of non-contact mapping. Care has to be taken in the analysis and interpretation of non-contact mapping studies, as chamber size and filter settings have a large effect on the appearance of the activation maps produced. Despite this limitation the majority of VT exit sites and part of the diastolic pathway can be identified with non-contact mapping techniques.

Background: The mechanisms how the activation within the pulmonary vein (PV) drives the atrial fibrillation (AF) has not been elucidated. Objectives: To define the AF maintenance mechanism by PV, we analyzed the activation sequence within the PV during AF. Methods: Selective endocardial mapping of the left superior PV (LSPV) was performed during AF in 11 patients with paroxysmal AF using a three-dimensional non-contact mapping system (EnSite 3000). In addition, we analyzed how the circumferential radiofrequency energy applications around the LSPV alter the activation of the LSPV and terminate AF. Results: Complex fractionated electrograms (CFE) were observed at the second half of the proximal LSPV at the roof (n=5), ridge (n=11) and carina (n=7). Mean CFE area was 9.1±3.4 cm2, which occupied the 19.8% of the LSPV area. Frequent episodes of pivoting activation associated with wave break and fusion was observed at this CFE area. The frequency of pivoting activation around the functional conduction block, wave break and fusion at the CFE region were significantly higher than those at the non-CFE region (32.5±12.2 vs. 4.6±5.8 times/sec; p Conclusions: AF was driven by the high frequent episodes of pivoting activation associated with wave break and wave fusion observed over the CFE area at the proximal PV. Linear lesions along the left PV including CFE area of the LSPV eliminate the meandering activation over the CFE area, resulting in the termination of AF.

Introduction: In this report we describe our experience using non-contact mapping for radiofrequency ablation in patients with inappropriate sinus tachycardia. Methods and Results: Two female patients with persistent complaints of palpitations and documented inappropriate sinus tachycardia with failed medical management underwent radiofrequency ablation using non-contact mapping. Non-contact mapping provided a continuous determination of the site of earliest breakthrough, facilitating the delivery and the assessment of the results of each radiofrequency application. Conclusion: Non-contact mapping is an effective mapping modality in the interventional treatment of inappropriate sinus tachycardia.

Beim Non-Contact-Mapping-Verfahren handelt es sich im Gegensatz zu den bisherigen sequentiellen konventionellen und dem elektroanatomischen Mappingverfahren um ein simultanes Mappingverfahren. Mit dem Non-Contact-Mapping ist es nun moglich, aus den Fernpotentialen uber 3 000 unipolare, endokardiale, virtuelle Elektrogramme uber ein mathematisches Modell zu berechnen, die dann auf ein dreidimensionales (3-D) Modell der zu untersuchenden Herzhohle projiziert werden. Dadurch wird ein dynamisches farbiges Aktivierungsmuster erzeugt, das die Potentiale an uber 3 000 Stellen der Endokardoberflache simultan anhand eines Schlages darstellt und somit ein 3-D-Isopotentialmapping in Echzeit ermoglicht. Der Stellenwert des Non-Contact-Mappings bei der Katheterablation von Vorhofflimmern liegt neben der 3-D-Darstellung des linken Vorhofs in der Identifizierung der arrhythmogenen Foci, d. h. der arrhythmogenen Pulmonalvene, auch bei seltenem Auftreten und insbesondere bei der Uberprufung der Kontinuitat der linearen Lasionen. Im Folgenden werden die Methodik und die Ergebnisse unterschiedlicher Ablationsstrategien bei Vorhofflimmern mit dem Non-Contact- Mapping-Verfahren beschrieben.

Idiopathic, focal ventricular tachycardia that originates from the right ventricular apex is presented. Arrhythmogenic ventricular dysplasia needs to be ruling out prior to making this diagnosis. This is a rare entity that can be cured with an ablation and therefore it needs to be considered in the differential diagnosis of idiopathic VTs before implanting a defibrillator.

Background Cardiac magnetic resonance (CMR) imaging enables characterization of myocardial scar and the ‘grey zone’, an admixture of scar and healthy myocardium, which is an independent predictor of ventricular arrhythmia. We explored the relationship between the grey zone and ventricular tachycardia circuits (VT) in ischaemic cardiomyopathy. Methods Two patients with previous myocardial infarct underwent high-resolution late gadolinium enhanced CMR scar imaging (1.2x1.2x2.6mm) and a VT-stimulation study. The LV scar core was segmented using full-width-half-maximum method; and the grey zone was segmented with a cut-off signal intensity below that of the scar core and above 2 standard-deviation of the remote healthy myocardium. A multi-electrode array (MEA) was positioned in the LV cavity for simultaneous electroanatomical mapping during the study. The MEA shell was registered with the CMR-derived LV shell using anatomical landmark registration (Figure 1a,b) for comparison. Results Sustained monomorphic VT (SMVT) was induced in both patients. Scar core and grey zone regions correlated well with the low voltage area (≤ 30% maximum voltage) seen on the MEA (Figure 1a,c,d). The exit point during SMVT

Summary We describe an 81-year-old man with multiple focal atrial tachycardias (ATs) originating from the tricuspid annulus. Non-contact mapping showed 3 incessant ATs, originating from the vicinity of His bundle region, inferior portion of coronary sinus ostium, and coronary sinus ostium, and 2 premature atrial contractions (PACs) originating from the tricuspid annulus in the 5 o’clock position and 6 o’clock position in the left anterior oblique view. Radiofrequency energy application to these 5 sites successfully eliminated the ATs and PACs. The patient has remained free from ATs or any symptoms without medication during the 16-month follow-up period. Non-contact mapping was useful in identifying the multiple AT origins, especially even if the tachycardia origin shifted occasionally or the tachycardia was non-sustained.

Aims Identification of arrhythmogenic scar using non-contact (NC) sinus rhythm (SR) mapping is limited. Dynamic substrate mapping (DSM) overcomes these limitations but is less accurate than plunge needle electrode mapping. We developed a revised method for calculating DSM which was validated using detailed histological analysis and compared with conventional mapping modalities. Methods and results Mapping was performed in eight sheep, >9 weeks post-myocardial infarction. Twenty multielectrode needles were deployed at thoracotomy in the left ventricle within and surrounding scar, and located using Ensite. Simultaneous catheter, needle, and NC electrograms were recorded during SR and multisite pacing. Dynamic substrate mapping maps were calculated as the maximum local peak negative voltage (PNV). Absolute mean DSM (AMDSM) maps, based on peak–peak voltage (P–PV), were calculated to minimize local pacing effects and take into account anisotropic influence. Dynamic substrate mapping and AMDSM maps were normalized based on global maximum voltages attained. Histologically quantified scar and mapping criteria were compared using Spearman's correlation and receiver operator curves (area under the curve, AUC) using 50% scar cut-off. For unipolar mapping, needles had greatest sensitivity at identifying scar which was better for P–PV (AUC; needle = 0.90, catheter = 0.70, NC = 0.66) than for PNV (AUC; needle = 0.79, NC = 0.38). AMDSM (AUC = 0.75) had superior scar discrimination than either catheter (AUC; unipolar = 0.70, bipolar = 0.71) or DSM (AUC = 0.67). Absolute mean DSM accuracy was improved when valvular geometries were excluded (AUC = 0.77). Conclusion Absolute mean DSM was comparably accurate in identifying scarred myocardium as PNV needle mapping but was superior to conventional catheter and NC mapping.

SUMMARY 1 The purpose of the present study was to explore the relationship between electrocardiogram (ECG) patterns of right ventricular outflow tract (RVOT) premature ventricular contractions and the three-dimensional distribution of the target sites. 2 Thirty-three consecutive patients were included in the study. The target sites were identified by non-contact mapping and confirmed by successful ablation. The distribution of the target sites in the three-dimensional reconstructed geometry of the RVOT was classified in three directions: (i) anterior (A)/posterior (P); (ii) free wall (F)/septal (Se); and (iii) superior (Su)/inferior (I). The ECG characteristics were then analysed according to the three-dimensional distribution of the target sites. 3 The following indices were helpful to identify the position of the target site: (i) QRS duration (≥ 150 msec = F

Introduction CRT is established therapy for patients with symptomatic heart failure, poor LV function & evidence of dyssynchrony. Hypothesis CRT outcomes may be improved by understanding of patient-specific conduction through electrical recruitability (ER) maps of the LV which can be derived from LV electrical activation (EA) data & electrophysiology (EP) models. Methods Patients scheduled for CRT underwent cardiac MRI in our hybrid X-ray/MRI (XMR) laboratory to delineate scar using late gadolinium enhancement (LE). An EP study was performed in the same procedure. An Eikonal EP model was used to predict propagation wavefronts in different pacing modes. ER was defined as the square of the tissue space constant of EA & was estimated by an adaptive algorithm by matching the simulated to the recorded activation times. Activation maps were recorded in various pacing modes using non-contact mapping (NCM). Results Ten patients underwent combined MRI & EP study. Fig 1a shows the estimated ER for a patient with activation recorded in sinus rhythm (SR) & corresponding % thickness LE from cardiac MRI (Fig 1b ). The correspondence of low recruitability areas (blue) to positive LE areas is evident. Further, an endocardial paced isochronal map was then predicted using the EP model with the SR ER map (Fig 1c ) & compared against NCM isochrones obtained (Fig 1d ) pacing in that position. Conclusion We have shown the proof of concept for estimating the electrical recruitability of myocardial tissue. Such maps may provide insights into the electrical properties of the tissue and assist in prediction of activation patterns resulting from pacing and may have a role in optimization of CRT pacing lead positions. Fig. 1. Bull’s eye plots for a patient with ischemic cardiomyopathy, posterolateral scar and LBBB. LV apex at centre of each diagram and basal segment on outside; anatomical orientation as indicated in (a) top left; Electrical recruitablility (units=mm 3 ) obtained in sinus rhythm (b) bottom left: percentage wall thickness of late enhancement (LE) (0=no LE; 1= full thickness LE) (c) top right; predicted isochronal map (earliest in red to latest in blue, units= msec) for LV endocardial pacing based on estimated recruitability and (d) bottom right corresponding measured activation pattern measured using NCM. (IVS: Interventricular septum)

The determination of dynamic changes in ventricular repolarization may provide insight into arrhythmogenic mechanisms as a consequence of pacing site. This study investigated acute pacing site effects on global characteristics of electrical restitution using high resolution, non-contact mapping (NCM).Activation-recovery intervals (ARIs) were determined from reconstructed left ventricular electrograms by the NCM system and were analysed during pacing from the right atrial appendage (RAA, intrinsic), right ventricular apex (RVA), and right ventricular septum (RVS) with extrasystoles delivered at intermediate and short coupling intervals in anesthetized swine (n = 5). Electrical restitution curves were determined by the S1-S2 pacing protocol. Activation-recovery interval restitution slopes were determined by the overlapping linear segments regression method. Global distribution of repolarization was defined as the coefficient of variation of the ARIs during restitution. The maximum ARI slopes yielded by RVA pacing were significantly greater than RAA pacing (0.44 vs. 0.32; P0.05) and RVS pacing (0.44 vs. 0.37; P = 0.05). There was no significant difference between RAA and RVS pacing (0.32 vs. 0.37). The global distribution of ARIs during restitution from RVA pacing was significantly greater than RAA pacing (12.0 vs. 8.1%; P0.05).Right ventricular apex pacing is associated with impaired global repolarization patterns compared to RAA and RVS. These observations support the hypothesis that RVA pacing may be associated with increased risk of ventricular arrhythmias compared to RVS pacing.

Background This study is aimed to assess the initiation and maintenance mechanisms of atrial fibrillation (AF) and their relationships with the anatomical structures of the left atrium (LA) and pulmonary veins (PVs). Methods Thirty-seven patients (pts; 33 men, mean age 50±12, range 25–68 years) with paroxysmal AF ( n =29) and persistent AF ( n =8) who underwent mapping of the LA and PV using 3D non-contact endocardial mapping system (EnSite 3000) were included. Atrial premature complexes (APCs) which triggered the initiation of AF lasted longer than 1 min were mapped and the activation sequence on isopotential color maps was analyzed. Results Wave front dynamics and the relationship with the underlying anatomical structures were assessed. APCs from PV were related to the initiation of AF, but not to the maintenance of AF in 59.5% of the pts (focally triggered type) whereas APCs from PV not only initiated AF but also maintained AF without continuous triggering in 27% (focally driven type). Mixed type and indeterminate type of AF was in 4.5% and 13.5%, respectively. During AF, the mean number of wavelet was 1.45 (maximum 3 in 76.5%). Anatomical structures showing frequent wave break and slow conduction were mostly located at the septopulmonary bundle (86.5%) and the posterior LA roof between left superior PV and right superior PV (54.1%). Conclusion Focal repetitive activity from PV played an important role in both initiation and maintenance of AF using NCM study. Specific anatomical structures such as septopulmonary bundle or posterior LA roof were associated with the spontaneous wave break and heterogeneous conduction delay, which was also appears to be important in the maintenance of AF.

Focal left atrial (LA) tachycardias/ectopy (LATs) that may initiate atrial fibrillation (AF) are often difficult to initiate, non-sustained, and may have multiple origins, often in one or more pulmonary veins (PV). Thus, mapping with conventional techniques is often difficult. The authors tested the hypothesis that a non-contact mapping system capable of global simultaneous mapping of >3000 points in the LA, would facilitate ablation of LAT. The non-contact mapping system was able to rapidly identify the origin of human LATs and focal AF despite the infrequency and short duration of initiating ectopy and guide a conventional mapping catheter to successful ablation sites. The authors also observed that, although isoproterenol is the most successful method of initiating LATs, these originate from multiple sites and therefore appear to be of limited clinical significance.

The currently available technology for the diagnosis of arrhythmias is capable of diagnosing only stable, patient tolerated arrhythmias: single-beat electrophysiologic imaging of the heart's electrical activity is not possible with currently available technology. For some sort of arrythmias (e.g., non-sustained atrial tachycardia) a system capable to do so seems to be of high value.

The pattern of left atrial (LA) activation during sinus rhythm (SR) in humans has not been delineated. The authors used a non-contact mapping system to analyze the patterns of left atrial (LA) activation during sinus rhythm and pacing. The system is capable of simultaneously reproducing more than 3,000 electrograms, which are superimposed on a virtual left atrial endocardium. Data were recorded in sinus rhythm and during pacing from the high right atrium, coronary sinus os, and right atrial septum. The authors demonstrate that during sinus rhythm, the LA activates mainly through posterior septal fibers, adjacent to the ostia of the right pulmonary veins. This suggests that, in humans, anterior interatrial connections including Bachmann's bundle may be less important than previously recognized.

Objectives Limited data exists about long term success rate after ablation of right ventricular outflow tract (RVOT) ventricular arrhythmias (VA) guided by the non-contact mapping system (NCM). In this study, we aim to investigate long term outcomes following NCM guided RVOT VA ablation. Methods From June 2006 to December 2011, consecutive patients with RVOT VA underwent mapping and ablation using NCM (group A, n = 136) or 3-D contact mapping system (control group B, n = 18). Within group A, ablation was randomised to be initiated at either the site of earliest electrical activity (EA site) or the break-out site from which rapid centrifugal electrical propagation originated from (BO site). Clinic visits, ECGs and 24 hour Holters were conducted monthly for the first three months and then in six months intervals. Results 154 (60 male, mean age 41.8 ± 13.5 years old) consecutive patients were enrolled. With follow up of 36.2 ± 17.5 months, the long term success rate after a single procedure without anti-arrhythmic agents was 86.8% (118/136) in the NCM cohort. Baseline characteristics, acute and long term success rates, complications were similar between Groups A and B. A learning curve of 20 cases was associated with the use of NCM. The initial ablation is more successful when directed at the EA sites rather than the BO sites identified by NCM (p Conclusions NCM-guided RVOT VA ablation is highly effective and associated with long term clinical outcomes comparable to ablation guided by 3-D mapping systems. Ablation is more successful when directed at the EA sites identified by the NCM.

Results from cardiac resynchronisation therapy are likely to improve as methods for identifying likely responders and the optimum site for lead placement become more refined

Objectives The spatial resolution between activation and pace mapping for idiopathic ventricular arrhythmia is still controversial. In this study, we further analysed pacemap spatial resolution and compare it to non-contact activation mapping. Methods The earliest activation from unipolar based non-contact mapping can be classified as the earliest activation (EA) and the breakout (BO) sites. A total of 124 patients (mean age was 43.65±12.74 years old) with 124 VT/PVCs, 36 male, were included in this study. A standard pace mapping at twice the diastolic threshold was applied at both EA and BO sites and the area of activated myocardium (EAA) and the area of captured myocardium (ECA) were measured based on activation and pace maps respectively. Initial ablation attempt was randomised at either the EA site or the BO site. If initial RF attempt failed, it would be followed by a crossover ablation. Results The overall acute successful rate was 98.39% (122/124 VT/PVCs). Ablation was succeeded at the BO site in 40 (32.79%) VT/PVCs, and at the EA site in 82 (67.21%) VT/PVCs, p 2 vs 0.03±0.13 cm 2 , 8.34±4.36 cm 2 vs 0.95±1.41 cm 2 , p 2 vs 0.75±0.50cm 2 , 10.89±5.08 cm 2 vs 8.31±4.97 cm 2 , p Conclusions Activation mapping provides better spatial resolution than pace mapping for identifying the origin of RVOT VT/PVCs.