The safety and efficacy of electroanatomical mapping (EAM)-guided device implantation.

BACKGROUND: The conventional method of device implantation requires fluoroscopic guidance. With the guidance of three-dimensional (3-D) navigation systems, devices can be implanted with minimal use of fluoroscopy. To date, this technique has been reported in several case reports in young, pregnant patients. However, this technique has not been widely utilized by electrophysiologists, despite offering several benefits, including reduced radiation exposure for the patient and the operator. METHODS: In this study, we evaluated 18 patients who successfully underwent device implantation with limited use of fluoroscopy under the guidance of the EnSite Precision 3-D mapping navigation system (Abbott, St. Paul, MN, USA). In most of the patients, the total fluoroscopy time was 1 s, accounted by a single postprocedural frame to insure appropriate lead placement. RESULTS: A total of 19 leads were implanted in 18 patients (14 male, four female) using the electroanatomical mapping (EAM)-guided technique. A total of 19 leads were implanted in 15 patients (10 male, five female) using the conventional method. The average length of stay was 1.20 days in the EAM group compared to 1.47 days in the conventional group (P = .10). Majority of the devices implanted in both groups were single-chamber implantable cardiac defibrillators (VVI ICD, Abbott) implanted for cardiomyopathy with left ventricular ejection fraction persistently below 35%, including 88% (16/18) in the EAM group compared to 73% (11/15) in the conventional group. No periprocedural or immediate postprocedure complications were reported in either group. Device parameters, including impedance, capture time, and capture voltage, showed no significant difference in either group. Total radiation time and radiation dose were markedly lower in the EAM-guided implantation group. CONCLUSIONS: In patients who meet appropriate criteria for device implantation, the use of EAM system offers a safe, practical, efficacious alternative method to device implantation, with significant reduction in radiation time and dose.

Characteristics, Mechanism and Long-Term Ablation Outcome of Atrial Tachycardias After Mitral Valvular Surgery and Concomitant Cox-MAZE IV Procedure.

The incidence of atrial tachycardia (AT) after rheumatic mitral valvular (RMV) surgery has been well described. However, there have been few reports on the characteristics, mechanism, and long-term ablation outcome of ATs after RMV surgery and concomitant Cox-MAZE IV procedure.The present study reviewed consecutive patients who underwent AT ablation between May 2008 and July 2013. All patients were refractory to antiarrhythmic drugs (AADs) and had a history of RMV surgery and Cox-MAZE IV procedure. A total of 34 patients underwent AT ablation after RMV surgery and concomitant Cox-MAZE IV procedure, and presented 57 mappable and 2 unmappable ATs. The 57 mappable ATs included 14 focal-ATs and 43 reentry-ATs. Ten of the 14 focal-like ATs were located at the pulmonary vein (PV) antrum and border of a box lesion. Of the 43 reentry-ATs, 16 were marco-reentrant around the mitral annulus (MA) and 16 around the tricuspid annulus. There were 41 atypical ATs (non-cavotricuspid isthmus related) including 16 ATs related to the box lesion and 21 ATs related to other Cox-MAZE IV lesions. The AT were successfully terminated in 33 (97.1%) patients. After mean follow-up of 46.9 ± 15.7 months, 25 (73.5%) patients maintained sinus rhythm without AADs after a single procedure and 28 (82.4%) patients after repeated procedures.The recurrent ATs after RMV surgery and concomitant Cox-MAZE IV were mainly reentry mechanism, and largely related to LA. An incomplete lesion or re-conductive gaps in a prior lesion might be the predominant mechanisms for these ATs. Catheter-based mapping and ablation of these ATs seems to be effective and safe during a long-term follow-up.

Development of simulation combining a physical heart model and three-dimensional system for electrophysiology training.

BACKGROUND: A new three-dimensional heart anatomical simulator (3D HAS) has been created combining a physical heart model with an electroanatomic mapping (EAM) system. The aim of this study is to describe the development and the validation process of this device. METHODS: We developed the 3D HAS combining a physical heart model with an EAM system. This simulator was then validated by 10 electrophysiologists, subdivided in two groups based on their experience in electrophysiology procedures. The performance of the experts was compared to the one of the novices in achieving three different tasks: fluoroless reconstruction of the right atrium, coronary sinus cannulation, and deployment of a linear ablation lesion in the cavotricuspid isthmus. For each operator, a score was calculated based on objective parameter for each task and for the overall performance. RESULTS: The 3D HAS was located in an environment that allowed use of the main features of the EAM system including contact force sensing. No technical issue was encountered during the validation process. The experts' performance was significantly better than the one of the novices both overall (P = 0.009) and in each task (right atrium reconstruction, P = 0.016; coronary sinus cannulation, P = 0.008; ablation lesion, P = 0.03). CONCLUSIONS: The 3D HAS is reliable and allows use of the main features of an EAM system in the right atrium. The ability to discriminate different levels of experience suggests that this simulator is enough realistic and could be useful for electrophysiology training.

Correlation of right ventricular multielectrode endocardial unipolar mapping and epicardial scar.

AIMS: Prior studies identified a relationship between epicardial bipolar and endocardial unipolar voltage. Whether the relationship is valid with smaller multielectrode mapping catheters has not been reported. We explored the association of right ventricular (RV) endocardial unipolar voltage mapping with epicardial bipolar voltage mapping using a multielectrode mapping catheter. METHODS: Electrograms from patients who underwent multielectrode endocardial and epicardial RV electroanatomical mapping during ablation procedures were analyzed. Each endocardial mapping point was matched to the corresponding nearest epicardial point. The correlation between unipolar endocardial voltage and epicardial bipolar voltage was determined. The optimal unipolar threshold to detect epicardial low voltage (< 1.0 mV) and dense scar (0.5 mV) was calculated. RESULTS: A total of 4,895 points were analyzed. There was a significant correlation between endocardial unipolar and epicardial bipolar voltage (Spearman rho  =  0.499, P  =  < 0.001). The extent of the correlation was inversely associated with wall thickness. The receiver operator characteristic analysis of endocardial unipolar voltage predicting epicardial bipolar voltage of < 1.0 mV and < 0.5 showed an area under the curve of 0.769 and 0.812, respectively. The endocardial unipolar voltage that had the highest sensitivity and specificity in detecting epicardial bipolar voltage of < 1.0 mV and < 0.5 mV was 3.3 mV (70.3% sensitivity, 70.3% specificity), and 2.8 mV (sensitivity 73.8%, specificity 73.3%), respectively. CONCLUSION: Epicardial low voltage of the RV can be assessed by unipolar endocardial voltage using small multielectrode catheters. The strength of the association was inversely correlated with the wall thickness.

Simultaneous Biatrial High-Density (510-512 Electrodes) Epicardial Mapping of Persistent and Long-Standing Persistent Atrial Fibrillation in Patients: New Insights Into the Mechanism of Its Maintenance.

BACKGROUND: The mechanism(s) of persistent and long-standing persistent (LSP) atrial fibrillation (AF) is/are poorly understood. We performed high-density, simultaneous, biatrial, epicardial mapping of persistent and LSP AF in patients undergoing open heart surgery (1) to test the hypothesis that persistent and LSP AF are due to ≥ 1 drivers, either focal or reentrant, and (2) to characterize associated atrial activation. METHODS AND RESULTS: Twelve patients with persistent and LSP AF (1 month to 9 years duration) were studied at open heart surgery. During AF, electrograms were recorded from both atria simultaneously for 1 to 5 minutes from 510 to 512 epicardial electrodes with ECG lead II. Thirty-two consecutive seconds of activation sequence maps were produced per patient. During AF, multiple foci (QS unipolar atrial electrograms) of different cycle lengths (mean, 175 ± 18 ms) were present in both atria in 11 of 12 patients. Foci (2-4 per patient, duration 5-32 s) were either sustained or intermittent, were predominantly found in the lateral left atrial free wall, and likely acted as drivers. Random and nonrandom breakthrough activation sites (initial r or R in unipolar atrial electrograms) were also found. In 1 of 12 patients, only breakthrough sites were found. All wave fronts emanated from foci and breakthrough sites, and largely either collided or merged with each other at variable sites. Repetitive focal QS activation occasionally generated repetitive wannabe reentrant activation in 5 of 12 patients. No actual reentry was found. CONCLUSIONS: During persistent and LSP AF in 12 patients, wave fronts emanating from foci and breakthrough sites maintained AF. No reentry was demonstrated.

Multielectrode contact mapping to assess scar modification in post-myocardial infarction ventricular tachycardia patients.

Substrate-based approaches for ablation of unmappable ventricular tachycardia (VT) are strictly dependent on high-density mapping of the scar. Ultra-high-density mapping with multielectrode catheters facilitates an accurate and faster definition of sites critical for re-entry, due to the possibility of simultaneous recordings of local potential from different pairs of electrodes. Multipolar catheters can be advanced to map the endocardial or the epicardial surface. A strong correlation between the scar area determined by electroanatomical mapping and the histopathological scar size has been demonstrated. A double-transeptal technique allows for an accurate definition of target sites. The complex scar architecture has been investigated by ultra-high-density mapping, let the identification of islets of heterogeneity where electrograms adjacent to the preserved myocardium have an higher incidence of late potentials. Pacing manoeuvres can easily be performed from any pair of electrode, to demonstrate the involvement of late potentials into the VT circuit. This strategy allows for a clear-cut validation of late potential abolishment, and may offer advantages to shorten procedural and fluoroscopy times. Large series are necessary to definitively assess the potential role of multielectrode mapping as a guide for the substrate ablation approach in post-myocardial infarction VT patients.

Endocardial-Epicardial Phase Mapping of Prolonged Persistent Atrial Fibrillation Recordings: High Prevalence of Dissociated Activation Patterns.

BACKGROUND: Endocardial-epicardial dissociation and focal breakthroughs in humans with atrial fibrillation (AF) have been recently demonstrated using activation mapping of short 10-second AF segments. In the current study, we used simultaneous endo-epi phase mapping to characterize endo-epi activation patterns on long segments of human persistent AF. METHODS: Simultaneous intraoperative mapping of endo- and epicardial lateral right atrium wall was performed in patients with persistent AF using 2 high-density grid catheters (16 electrodes, 3 mm spacing). Filtered unipolar and bipolar electrograms of continuous 2-minute AF recordings and electrodes locations were exported for phase analyses. We defined endocardial-epicardial dissociation as phase difference of ≥20 ms between paired endo-epi electrodes. Wavefronts were classified as rotations, single wavefronts, focal waves, or disorganized activity as per standard criteria. Endo-Epi wavefront patterns were simultaneously compared on dynamic phase maps. Complex fractionated electrograms were defined as bipolar electrograms with ≥5 directional changes occupying at least 70% of sample duration. RESULTS: Fourteen patients with persistent AF undergoing cardiac surgery were included. Endocardial-epicardial dissociation was seen in 50.3% of phase maps with significant temporal heterogeneity. Disorganized activity (Endo: 41.3% versus Epi: 46.8%, P=0.0194) and single wavefronts (Endo: 31.3% versus Epi: 28.1%, P=0.129) were the dominant patterns. Transient rotations (Endo: 22% versus Epi: 19.2%, P=0.169; mean duration: 590±140 ms) and nonsustained focal waves (Endo: 1.2% versus Epi: 1.6%, P=0.669) were also observed. Apparent transmural migration of rotational activations (n=6) from the epi- to the endocardium was seen in 2 patients. Electrogram fractionation was significantly higher in the epicardium than endocardium (61.2% versus 51.6%, P<0.0001). CONCLUSIONS: Simultaneous endo-epi phase mapping of prolonged human persistent AF recordings shows significant Endocardial-epicardial dissociation marked temporal heterogeneity, discordant and transitioning wavefronts patterns and complex fractionations. No sustained focal activity was observed. Such complex 3-dimensional interactions provide insight into why endocardial mapping alone may not fully characterize the AF mechanism and why endocardial ablation may not be sufficient. Graphic Abstract: A graphic abstract is available for this article.

The Future of Percutaneous Epicardial Interventions.

The pericardial space provides a unique vantage point to access different cardiac structures for diagnosis and treatment of arrhythmias and other nonelectrophysiologic conditions, such as heart failure. There have been notable innovations to improve safety of percutaneous pericardial access and its use for various procedures. Percutaneous pericardial device therapies for pacing and defibrillation have been in development, success of which will be a significant advance in treatment of bradyarrhythmias, cardiac resynchronization therapy, and prevention of arrhythmic deaths. There is need for continued efforts in development and expansion of this technique and a systematic approach to monitor efficacy and safety outcomes.

The use of a high-resolution mapping system may facilitate standard clinical practice in VE and VT ablation.

BACKGROUND: First experiences using a 64-electrode mini-basket catheter (BC) paired with an automatic mapping system (Rhythmia™) for catheter ablation (CA) of ventricular ectopy (VE) and ventricular tachycardia (VT) have been reported. OBJECTIVES: We aimed to evaluate (1) differences in ventricular access for the BC and (2) benefit of this technology in the setting of standard clinical practice. METHODS: Patients (pts) undergoing CA for VE or VT using the Intellamap Orion™ paired with the Rhythmia™ automated-mapping system were included in this study. For LV access, transseptal and retrograde access were compared. RESULTS: All 32 pts (29 men, age 63 ± 15 years) underwent CA for VE (17 pts) or VT (15 pts). For mapping of VE originating from the left ventricle (LV) in 10 out of 13 pts, a transaortic access was feasible. The predominant access for CA of VT was transaortic (5/7). Feasibility and safety seem to be equal. The total procedure time was 179.1 ± 21.2 min for VE ablation and 212.0 ± 71.7 min for VT ablation (p = 0.177). For VE, an acquisition of 1602 ± 1672 map points and annotation of 140 ± 98 automated mapping points sufficed to abolish VE in all pts. During a 6-month follow-up (FU) after CA for VE, a VE burden reduction from 18.5 ± 2.1% to 2.8 ± 2.2% (p = 0.019) was achieved. In VT pts, one patient showed recurrence of sustained VT episodes during FU. CONCLUSION: Use of a high-resolution mapping system for VE/VT CA potentially facilitates revelation of VE origin and VT circuits in the setting of standard clinical practice. Feasibility and safety of a venous, transaortic, transseptal, or a combined approach seem to be equal.

Detailed Analysis of the Relation Between Bipolar Electrode Spacing and Far- and Near-Field Electrograms.

OBJECTIVES: This study sought to evaluate the relation between bipolar electrode spacing and far- and near-field electrograms. BACKGROUND: The detailed effects of bipolar spacing on electrograms (EGMs) is not well described. METHODS: With a HD-Grid catheter, EGMs from different bipole pairs could be created in each acquisition. This study analyzed the effect of bipolar spacing on EGMs in 7 infarcted sheep. A segment was defined as a 2-mm center-to-center bipole. In total, 4,768 segments (2,020 healthy, 1,542 scar, and 1,206 in border areas, as defined by magnetic resonance imaging [MRI]) were covered with an electrode pair of spacing of 2 mm (Bi-2), 4 mm (Bi-4), and 8 mm (Bi-8). RESULTS: A total of 3,591 segments in Bi-2 were free from local abnormal ventricular activities (LAVAs); 1,630 segments were within the MRI-defined scar and/or border area. Among them, 172 (10.6%) segments in Bi-4 and 219 (13.4%) segments in Bi-8 showed LAVAs. In contrast, LAVAs were identified in 1,177 segments in Bi-2; 1,118 segments were within the MRI-defined scar and/or border area. Among them, LAVAs were missed in 161 (14.4%) segments in Bi-4 and in 409 (36.6%) segments in Bi-8. In segments with LAVAs, median far-field voltage increased from 0.09 mV (25th to 75th percentile: 0.06 to 0.14 mV) in Bi-2, to 0.16 mV (25th to 75th percentile: 0.10 to 0.24 mV) in Bi-4, and to 0.28 mV (25th to 75th percentile: 0.20 to 0.42 mV) in Bi-8 (p < 0.0001). Median near-field voltage increased from 0.14 mV (25th to 75th percentile: 0.08 to 0.25 mV) in Bi-2, to 0.21 mV (25th to 75th percentile: 0.12 to 0.35 mV) in Bi-4, and to 0.32 mV (25th to 75th percentile: 0.17 to 0.48 mV) in Bi-8 (p < 0.0001). The median near-/far-field voltage ratio decreased from 1.67 in Bi-2, to 1.43 in Bi-4, and 1.23 in Bi-8 (p < 0.0001). CONCLUSIONS: Closer spacing better discriminates surviving tissue from dead scar area. Although far-field voltage systematically increases with spacing, near-field voltages were more variable, depending on local surviving muscular bundles. Near-field EGMs are more easily observed with smaller spacing, largely due to the reduction of the far-field effect.

Epicardial Ventricular Tachycardia Ablation Guided by a Novel High-Resolution Contact Mapping System: A Multicenter Study.

Background Mapping using a multipolar catheter with small and closely spaced electrodes has been shown to improve the validity of electrograms to identify endocardial critical sites of reentry isthmus and foci of earliest activation. However, the feasibility, safety, and clinical outcome of using such technology to guide epicardial ventricular tachycardia (VT) ablation has not been reported. Methods and Results Thirty-three consecutive patients from 5 high-volume centers were studied. These patients had 43 epicardial maps using a novel 64-pole mini-basket catheter to guide VT ablation. Activation maps with 17 832 points per map (interquartile range: 7621-32 497 points per map) were acquired in 11 patients with tolerated VT (7 focal, 4 reentry). Substrate maps with 40149 points per map (interquartile range: 20926-49391 points per map) were acquired in 30 patients. Local abnormal ventricular activities were consistently demonstrated at the substrate regions of interest. Epicardial ablation was performed in 31 of 33 patients, with acute VT termination in 10 of 11 patients (91%). Complete elimination of local abnormal ventricular activities was achieved in 25 of 31 patients. At a median follow-up of 10 months (interquartile range: 4-14 months), 64% (7/11) of patients who had acute termination of VT and 55% (11/20) of those who had substrate modification alone were free of VT. There was no immediate complication following epicardial procedure. Conclusions Epicardial VT ablation guided by a mini-basket catheter is feasible and safe. Complete reentry VT circuits and foci of earliest activation were identified in all inducible stable VT. The longer term clinical outcome of ablation guided by this novel mapping technology utilizing small and closely spaced electrodes will have to be determined with a larger study.

Relevance of Conduction Disorders in Bachmann's Bundle During Sinus Rhythm in Humans.

BACKGROUND: Bachmann's bundle (BB) is considered to be the main route of interatrial conduction and to play a role in development of atrial fibrillation (AF). The goals of this study are to characterize the presence of conduction disorders in BB during sinus rhythm and to study their relation with AF. METHODS AND RESULTS: High-resolution epicardial mapping (192 unipolar electrodes, interelectrode distance: 2 mm) of sinus rhythm was performed in 185 patients during coronary artery bypass surgery of whom 13 had a history of paroxysmal AF. Continuous rhythm monitoring was used to detect postoperative AF during the first 5 postoperative days. In 67% of the patients, BB was activated from right to left; in the remaining patients from right and middle (21%), right, central, and left (8%), or central (4%) site. Mean effective conduction velocity was 89 cm/s. Conduction block was present in most patients (75%; median 1.1%, range 0-12.8) and was higher in patients with paroxysmal AF compared with patients without a history of AF (3.2% versus 0.9%; P=0.03). A high amount of conduction block (>4%) was associated with de novo postoperative AF (P=0.02). Longitudinal lines of conduction block >10 mm were also associated with postoperative AF (P=0.04). CONCLUSIONS: BB may be activated through multiple directions, but the predominant route of conduction is from right to left. Conduction velocity across BB is around 90 cm/s. Conduction is blocked in both longitudinal and transverse direction in the majority of patients. Conduction disorders, particularly long lines of longitudinal conduction block, are more pronounced in patients with AF episodes.

Resolving Myocardial Activation With Novel Omnipolar Electrograms.

BACKGROUND: With its inherent limitations, determining local activation times has been the basis of cardiac mapping for over a century. Here, we introduce omnipolar electrograms that originate from the natural direction of a travelling wave and from which instantaneous conduction velocity amplitude and direction can be computed at any single location without first determining activation times. We sought to validate omnipole-derived conduction velocities and explore potential application for localization of sources of arrhythmias. METHODS AND RESULTS: Electrograms from omnipolar mapping were derived and validated using 4 separate models and 2 independent signal acquisition methodologies. We used both electric signals and optical signals collected from monolayer cell preparations, 3-dimensional constructs built with cardiomyocytes derived from human embryonic stem cells, simultaneous optical and electric mapping of rabbit hearts, and in vivo pig electrophysiology studies. Conduction velocities calculated from omnipolar electrograms were compared with wavefront propagation from optical and electric-mapping studies with a traditional local activation time-based method. Bland-Altman analysis revealed that omnipolar measurements on optical data were in agreement with local activation time methods for wavefront direction and velocity within 25 cm/s and 30°, respectively. Similar agreement was also found on electric data. Furthermore, mathematical operations, such as curl and divergence, were applied to omnipole-derived velocity vector fields to locate rotational and focal sources, respectively. CONCLUSIONS: Electrode orientation-independent cardiac wavefront trajectory and speed at a single location for each cardiac activation can be determined accurately with omnipolar electrograms. Omnipole-derived vector fields, when combined with mathematical transforms may aid in real-time detection of cardiac activation sources.

Calm Before the Storm: An Uncomplicated Epicardial Lead Extraction Resulting in DIC and Patient Demise.

A previously stable 77-year-old man with significant cardiac history underwent an uneventful extraction of a Citrobacter-infected and eroded pacemaker lead. His postoperative course was acutely complicated by respiratory failure and quickly progressed into disseminated intravascular coagulation, acute renal failure, shock liver, and ventricular tachycardic arrest. I believe that this is the first case report of such a drastic turn of events after a routine pacemaker lead extraction.

The effect of electrode density on the interpretation of atrial activation patterns in epicardial mapping of human persistent atrial fibrillation.

BACKGROUND: Mechanisms sustaining human persistent atrial fibrillation (AF) remain debated, with significant differences between high-density epicardial and global endocardial mapping studies. A key difference is the density of recording electrodes. OBJECTIVE: We aimed to determine the differences in the prevalence of different atrial activation patterns, and specifically in the prevalence of rotational activations, with varying densities of bipolar electrodes. METHODS: Epicardial mapping was performed in 10 patients undergoing cardiac surgery, with bipolar electrograms recorded using a triangular plaque (6.75 cm(2) area; 117 bipoles; 2.5-mm inter-bipole spacing) applied to the left atrial posterior wall or right atrial free wall. Dynamic wavefront mapping based on the timing of atrial electrograms was applied to 2 discrete 10-second AF segments. The spacing between bipolar electrode locations was increased from 2.5 × 3.5 mm in the horizontal and oblique directions to 5.0 × 3.5, 5.0 × 7.1, and 7.5 × 10.6 mm, with wavefront mapping repeated at each density. RESULTS: As density reduced, there was a significant change in relative proportions of the various activation patterns (F=3.69; P < .001). Simple broad wavefront activations became more prevalent (20% ± 8% to 54% ± 8%; P < .05) and complex patterns became less prevalent (48% ± 8% to 9% ± 8%; P < .05) with reducing density. The prevalence of rotational activity declined with bipole density, from median 5.0% (range 0.9%-12.1%) to 0% (range 0%-1.5%) (P = .03). The largest change occurred between inter-bipole spacings of 5.0 × 3.5 and 5.0 × 7.1 mm. CONCLUSION: Apparent activation patterns in persistent AF vary significantly with electrode density. Low density underestimates the prevalence of complex and rotational patterns. The largest difference occurs between an inter-bipole spacing of 5.0 × 3.5 and a spacing of 5.0 × 7.1 mm. This may have important implications for mapping technology design.

Impact of New Technologies and Approaches for Post-Myocardial Infarction Ventricular Tachycardia Ablation During Long-Term Follow-Up.

BACKGROUND: During the past years, many innovations have been introduced to facilitate catheter ablation of post-myocardial infarction ventricular tachycardia. However, the predictors of outcome after ablation were not thoroughly studied. METHODS AND RESULTS: From 2009 to 2013, consecutive patients referred for post-myocardial infarction ventricular tachycardia ablation were included. The end point of the procedure was complete elimination of local abnormal ventricular activities (LAVA) and ventricular tachycardia (VT) noninducibility. The predictors of outcome with primary end point of VT recurrence were assessed. A total of 125 patients were included (age: 64±11 years; 7 women) for 142 procedures. The left ventricle was accessed via transseptal, retrograde aortic, and epicardial approaches in 87%, 33%, and 37% of patients, respectively. Three-dimensional electroanatomical mapping system was used in 70%, multipolar catheter in 51%, and real-time image integration in 38% (from magnetic resonance imaging in 39% and multidetector computed tomography in 93%) of patients. Before ablation, VT was inducible in 75%, and endocardial/epicardial LAVA were present in 88%/75%. After ablation, complete LAVA elimination was achieved in 60%, and VT noninducibility in 83%. During a median follow-up of 850 days (interquartile range, 439-1707), VT recurrence was observed in 36%. Multivariable analysis identified 3 independent outcome predictors: the ability to achieve complete LAVA elimination (R(2)=0.29; P<0.0001; risk ratio=0.52 [0.38-0.70]), the use of real-time image integration (R(2)=0.21; P=0.0006; risk ratio=0.49 [0.33-0.74]), and the use of multipolar catheters (R(2)=0.08; P=0.05; risk ratio=0.75 [0.56-1.00]). CONCLUSIONS: Achievement of complete LAVA elimination and use of scar integration from imaging and multipolar catheters to focus high-density mapping are independent predictors of VT-free survival after catheter ablation for post-myocardial infarction ventricular tachycardia.

The importance of Purkinje activation in long duration ventricular fibrillation.

BACKGROUND: The mechanisms that maintain long duration ventricular fibrillation (LDVF) are unclear. The difference in distribution of the Purkinje system in dogs and pigs was explored to determine if Purkinje activation propagates to stimulate working myocardium (WM) during LDVF and WM pacing. METHODS AND RESULTS: In-vivo extracellular recordings were made from 1044 intramural plunge and epicardial plaque electrodes in 6 pig and 6 dog hearts. Sinus activation propagated sequentially from the endocardium to the epicardium in dogs but not pigs. During epicardial pacing, activation propagated along the endocardium and traversed the LV wall almost parallel to the epicardium in dogs, but in pigs propagated away from the pacing site approximately perpendicular to the epicardium. After 1 minute of VF, activation rate near the endocardium was significantly faster than near the epicardium in dogs (P<0.01) but not pigs (P>0.05). From 2 to 10 minutes of LDVF, recordings exhibiting Purkinje activations were near the endocardium in dogs (P<0.01) but were scattered transmurally in pigs, and the WM activation rate in recordings in which Purkinje activations were present was significantly faster than the WM activation rate in recordings in which Purkinje activations were absent (P<0.01). In 10 isolated perfused dog hearts, the LV endocardium was exposed and 2 microelectrodes were inserted into Purkinje and adjacent myocardial cells. After 5 minutes of LDVF, mean Purkinje activation rate was significantly faster than mean WM activation rate (P<0.01). CONCLUSION: These extracellular and intracellular findings about activation support the hypothesis that Purkinje activation propagates to stimulate WM during sinus rhythm, pacing, and LDVF.

Transcoronary mapping of ventricular asynchrony due to left bundle branch block in a porcine model.

BACKGROUND: Optimal positioning of the left ventricular (LV) lead at the latest activated part of the left ventricle is one of the major challenges in implantation of cardiac resynchronization therapy (CRT) devices with respect to ascertaining an optimal resynchronization effect resulting in a high responder rate. In the present study, we evaluated the feasibility of transcoronary measurement of LV electrical activation by a coated guidewire in a porcine model. METHODS AND RESULTS: Transcoronary measurement of ventricular activation was performed in 16 pigs under general anesthesia. Left bundle branch block (LBBB) was induced by transvenous pacing in the right ventricular apex (RVA). A specially coated guidewire (Vision Wire; Biotronik) serving as the different electrode was positioned subsequently in the proximal and distal part of each coronary main vessel. A cutaneous skin patch electrode was placed at the back of the thorax of the animal to act as the indifferent electrode. Both electrodes were connected to a portable electrophysiology lab system (EP Tracer 38; CardioTek). Mean QRS width during transvenous right ventricular pacing was 83 ± 5 ms with a typical LBBB pattern. The measured time interval between the beginning of the QRS complex in the surface electrocardiogram (ECG) and the local signal derived from the tip of the guidewire (QRS-EGM) was 32 ± 9 ms in the distal ramus circumflex (RCX) coronary artery and 51 ± 6 ms in the proximal RCX, yielding a mean delay of 18 ± 8 ms within this vessel. In the left anterior descending (LAD) coronary artery, the local signal was 23 ± 10 ms in the distal part and 41 ± 10 ms in the proximal part of the vessel, with an identical mean delay of 18 ± 8 ms. The QRS-EGM interval within the right coronary artery (RCA) was 14 ± 8 ms in the distal part and 40 ± 9 ms in the proximal part of the vessel, resulting in a mean delay of 25 ± 7 ms. The delay between the activation of the distal RCA and the activation of the distal LAD and RCX was statistically significant (P<.001). Within the proximal guidewire positions, the latest electrical activation of the left ventricle during pacing-induced LBBB could be observed in the RCX with 51.4 ± 6.3 ms (P<.01). CONCLUSION: Transcoronary measurement of LV excitation by a specially coated guidewire is feasible and could confirm the electrical asynchrony induced by LBBB. Since coronary angiography is a mandatory part of the evaluation of patients for CRT implantation, a "transcoronary mapping procedure" can be easily performed, thereby evaluating the latest activated part of the left ventricle in advance of the implantation procedure, aiming to improve the responder rate in CRT therapy.