Non-contact Endocardial Mapping Research Articles

Absence of Rapid Propagation through the Purkinje Network as a Potential Cause of Line Block in the Human Heart with Left Bundle Branch Block.

Background: Cardiac resynchronization therapy is an effective device therapy for heart failure patients with conduction block. However, a problem with this invasive technique is the nearly 30% of non-responders. A number of studies have reported a functional line of block of cardiac excitation propagation in responders. However, this can only be detected using non-contact endocardial mapping. Further, although the line of block is considered a sign of responders to therapy, the mechanism remains unclear.Methods: Herein, we created two patient-specific heart models with conduction block and simulated the propagation of excitation based on a cellmodel of electrophysiology. In one model with a relatively narrow QRS width (176 ms), we modeled the Purkinje network using a thin endocardial layer with rapid conduction. To reproduce a wider QRS complex (200 ms) in the second model, we eliminated the Purkinje network, and we simulated the endocardial mapping by solving the inverse problem according to the actual mapping system.Results: We successfully observed the line of block using non-contact mapping in the model without the rapid propagation of excitation through the Purkinje network, although the excitation in the wall propagated smoothly. This model of slow conduction also reproduced the characteristic properties of the line of block, including dense isochronal lines and fractionated local electrocardiograms. Further, simulation of ventricular pacing from the lateral wall shifted the location of the line of block. By contrast, in the model with the Purkinje network, propagation of excitation in the endocardial map faithfully followed the actual propagation in the wall, without showing the line of block. Finally, switching the mode of propagation between the two models completely reversed these findings.Conclusions: Our simulation data suggest that the absence of rapid propagation of excitation through the Purkinje network is the major cause of the functional line of block recorded by non-contact endocardial mapping. The line of block can be used to identify responders as these patients loose rapid propagation through the Purkinje network.

Simultaneous Epicardial and Noncontact Endocardial Mapping of the Canine Right Atrium: Simulation and Experiment

Epicardial high-density electrical mapping is a well-established experimental instrument to monitor in vivo the activity of the atria in response to modulations of the autonomic nervous system in sinus rhythm. In regions that are not accessible by epicardial mapping, noncontact endocardial mapping performed through a balloon catheter may provide a more comprehensive description of atrial activity. We developed a computer model of the canine right atrium to compare epicardial and noncontact endocardial mapping. The model was derived from an experiment in which electroanatomical reconstruction, epicardial mapping (103 electrodes), noncontact endocardial mapping (2048 virtual electrodes computed from a 64-channel balloon catheter), and direct-contact endocardial catheter recordings were simultaneously performed in a dog. The recording system was simulated in the computer model. For simulations and experiments (after atrio-ventricular node suppression), activation maps were computed during sinus rhythm. Repolarization was assessed by measuring the area under the atrial T wave (ATa), a marker of repolarization gradients. Results showed an epicardial-endocardial correlation coefficients of 0.80 and 0.63 (two dog experiments) and 0.96 (simulation) between activation times, and a correlation coefficients of 0.57 and 0.46 (two dog experiments) and 0.92 (simulation) between ATa values. Despite distance (balloon-atrial wall) and dimension reduction (64 electrodes), some information about atrial repolarization remained present in noncontact signals.

Activation patterns during selective pacing of the left ventricle can be characterized using noninvasive electrocardiographic imaging

Background Noncontact endocardial mapping allows accurate beat-to-beat reconstruction of the reentrant pathway of ventricular tachycardia and improves outcomes after ablation. Several studies support electrocardiographic imaging (ECGI) as a means of noninvasively outlining epicardial activation despite constraints of internal geometry. However, few have explored its clinical application. This study aims to evaluate ECGI during selective left ventricular (LV) pacing, relative to an invasive approach. Methods Multisite pacing was performed within the left ventricles of 3 patients undergoing invasive procedures. Simultaneous recording of endocardial potentials using a noncontact multielectrode array and body surface potentials (BSP) using an 80-electrode torso vest was performed. A total of 16 recordings were made. The inverse solution was applied to BSP to reconstruct epicardial activation. Single-paced beats from real and virtual electrograms were used to construct 3-dimensional isochronal and isopotential maps. Endocardial and epicardial data were then superimposed onto a single geometry to allow quantitative comparison of activation foci. Results Good correlation was observed between endocardial activation patterns and those reconstructed from BSP using ECGI. This was repeatedly demonstrated in all LV regions except for the septum (3 recordings). Epicardial isochronal maps were able to locate early and late activation to mean distances of 13.8 ± 4.7 and 12.5 ± 3.7 mm from endocardial data. Isopotential maps localized pacing sites with comparable accuracy (14 ± 5.3 mm). Conclusions Body surface potentials and reconstructed epicardial activation patterns during LV pacing correlate well with endocardial data acquired invasively. The exception was during pacing of the septum. Although early results are encouraging, further quantitative data are required to fully validate and apply this noninvasive tool in the clinical arena.

Mechanisms responsible for the initiation and maintenance of atrial fibrillation assessed by non-contact mapping system

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.

Catheter ablation of haemodynamically unstable or non-sustained ventricular tachycardia

Background — Ventricular tachycardia (VT) may be haemodynamically unstable or non-sustained, interfering with detailed activation mapping. Non-contact mapping permits beat-by-beat analysis of VT, projected upon a 3-dimensional reconstructed geometry of the cardiac chamber.Objective —The aim of the present study is to determine the utility of non-contact endocardial mapping to guide ablation of haemodynamically unstable VT or non-sustained VT.Methods and results — Eighteen VTs in 17 patients were induced (cycle length 336±58ms) and mapped. Three patients were mapped during premature ventricular complexes (PVCs) because sustained VT could not be induced. Analysis of the archived non-contact activation maps was performed to identify the exit point and/or the diastolic pathway of the VT reentry circuit.The endocardial exit points (10±16ms before QRS) were defined in 17/18 VTs (94%). A diastolic pathway was identified in 5/6 ischaemic VTs.The earliest activation sites were identified in all 3patients with PVCs. Radiofrequency current was applied around the exit point or to create a line of block across the diastolic pathway. Catheter ablation was performed in 17/18 VTs, including 3patients mapped using only PVCs. Ablation was successful in 16/18 VTs (89%) and in 15/17patients (82%). Catheter ablation was not performed in one patient (peri-hisian VT) and was unsuccessful in one patient (mapped during PVCs).Conclusions — Non-contact endocardial mapping is useful to guide radiofrequency catheter ablation of untolerated or non-sustained VTs.

Role of the Posterior Papillary Muscle and Purkinje Potentials in the Mechanism of Ventricular Fibrillation in Open Chest Dogs and Swine: Effects of Catheter Ablation

Papillary muscle (PM) ablation may terminate ventricular fibrillation (VF) in rabbit hearts. Whether or not PM ablation prevents ventricular fibrillation (VF) induction in large animals is unknown. We performed noncontact endocardial mapping and/or high-density epicardial mapping during VF in 12 dogs and 16 swine and tested the effects of posterior PM (PPM) ablation on VF inducibility. During VF in progressive global ischemia (3 swine and 2 dogs), the highest dominant frequency (DF) was near PPM. The majority of the reentrant wavefronts during a propranolol infusion (swine) were anchored to the PPM. Purkinje potentials onset were recorded on the PPM both during sinus rhythm and during VF. Radiofrequency (RF) ablation of the endocardium on the PPM with a linear extension of the ablation line from the PPM to the mitral valve annulus and then the left ventricular apex in 7 dogs reduced the VF inducibility from 100% at baseline to 22% after ablation (P < 0.0001). RF applications to the anterolateral wall of dogs (n = 3) did not prevent VF induction. The application of RF energy near the PPM frequently initiated VF in swine (n = 7), preventing subsequent testing of VF inducibility. In dogs and swine, the highest DF and majority of reentrant wavefronts during VF with acute global ischemia or during a propranolol infusion were located on the PPM. RF ablation targeted at the PPM reduced the inducibility of VF in normal dogs. However, the same ablation provoked incessant VF in swine, preventing subsequent testing of VF inducibility.

Electroanatomic Characteristics of Atrial Premature Beats Triggering Atrial Fibrillation in Patients with Persistent Versus Paroxysmal Atrial Fibrillation

APBs in Persistent Versus Paroxysmal AF. Although the electrical disconnection between the left atrium (LA) and pulmonary veins (PVs) by radiofrequency catheter ablation has been proven to be effective in controlling atrial fibrillation (AF), the recurrence rate is higher in patients with persistent AF (PeAF) than with paroxysmal AF (PAF). We hypothesized that the origin of the atrial premature beats (APBs) that trigger AF and the pattern of their breakthrough into the LA differ between PAF and PeAF. We mapped 75 APBs (53 APBs triggering AF, 22 isolated APBs) from the LA and PVs in 26 patients with AF (age: 49.5 +/- 9.6, males: 23, PAF = 17, PeAF = 9), using a noncontact endocardial mapping (NCM) system. The location of the preferential conduction (PC) sites and their conduction velocity (CV) were compared. In patients with PeAF, the earliest activation (EA) site and exit of the PC were more frequently located on the LA side of the LA-PV junction as compared with PAF (P < 0.001). Eighty-one percent of the PCs were located in the area between the left and right superior PVs. The incidence of PCs was similar between the PeAF and PAF patients (P = NS). PCs were more commonly found with APBs inducing AF (63.3%) than with those not inducing AF (35.2%, P = 0.01). The CV of the PC was slower for PeAF than PAF (P < 0.001). The CV in the LA during sinus rhythm was also slower for PeAF than PAF (P < 0.01). PeAF was more frequently triggered by APBs from the LA side of the LA-PV junction than PAF and resulted in slower conduction than did PAF. These findings may help explain the higher potential for recurrence after electrical PV isolation in patients with PeAF.

Rate‐Dependent Block in the Sinus Venosa of the Swine Heart during Transverse Right Atrial Activation: Correlation Between Electrophysiologic and Anatomic Findings

Rate-dependent block in the sinus venosa. Whether the crista terminalis or the sinus venosa result in rate-dependent block during transverse activation of the right atrial activation remains unknown. In the present study, right atrial activation at different cycle lengths was studied in the swine heart using high-resolution noncontact mapping (Endocardial Solutions). The location of the block was tagged and correlated with postmortem anatomical findings. Eight pigs were studied using noncontact mapping to obtain right atrial geometry and detailed sequence of activation using noncontact endocardial mapping. During sinus rhythm, activation proceeded uninterrupted craniocaudally along the sinus venosa and crista terminalis with similar conduction velocities (1.08+/-0.17 and 1.17+/-0.14 m/sec, respectively). Proximal coronary sinus stimulation was used to create transverse activation of the posterior right atrial wall. A rate-dependent decrease in conduction velocity occurred in the sinus venosa region (0.93+/-0.21, 0.82+/-0.14, and 0.52+/-0.09 m/sec at 500, 400, and 300 ms, respectively; P<0.05). The line of block verified by isopotential mapping and double potentials was obtained at cycle lengths of 240+/-30 ms. This line of the block was tagged with radiofrequency current lesions. Postmortem, all lesions were located in the sinus venosa region, 9.8+/-4.1 mm from the posteromedial edge of the crista terminalis. This region showed abrupt changes in muscle fiber thickness and orientation as well as in collagen content. The sinus venosa and not the crista terminalis results in a rate-dependent line of block during transverse right atrial activation. The morphologic characteristics of the sinus venosa appear to facilitate block in this region.

Initiation and Maintenance Mechanism of Atrial Fibrillation Assessed by 3-Dimensional Non-Contact Mapping System

Background and Objectives：We undertook this study 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). Subjects and Methods：Thirty-seven patients (33 men, mean age 50, 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 enrolled. The multielectrode array and ablation catheter were positioned in the LA via the double transseptal approach. Atrial premature beats (APBs) which triggered initiation of AF that lasted longer than 1 min were mapped and the activation sequence was analyzed on isopotential color maps. Wave front dynamics and the relationship with the underlying structures were assessed. Results：More than half, 56.4%, of APBs from PV were related to the initiation of AF, but not related to the maintenance of AF. A quarter, 25.6%, of APBs from PV not only initiated AF, but also maintained AF without continuous triggering. Mixed type and indeterminate type of AF was 5.0% and 12.8%, respectively. During AF, the mean number of wavelets was 1.45 (maximum 3 in 76.5%). Anatomical structures showing slow conduction and wavebreaks were mostly located at the septopulmonary bundle (86.5%) and the posterior roof of the LA between the left superior PV and right superior PV (54.1%). Conclusion：Focal repetitive activity from PV played an important role in both the initiation and maintenance of AF. Specific anatomical structures such as septopulmonary bundle or posterior roof of the LA were related to the heterogeneous conduction delay and spontaneous wavebreak,

Mechanisms responsible for the initiation and maintenance of atrial fibrillation assessed by noncontact endocardial mapping system

Mechanisms responsible for the initiation and maintenance of atrial fibrillation assessed by noncontact endocardial mapping system