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RETRO‐mapping was developed to automate activation mapping of atrial fibrillation (AF). We used the algorithm to study the effect of pulmonary vein isolation (PVI) on the frequency of focal, planar, and colliding wavefronts in persistent AF. An AFocusII catheter was placed on the left atrial endocardium to record 3 s of AF at six sites pre and post‐PVI in patients undergoing wide circumferential PVI for persistent AF. RETRO‐mapping analyzed each segment in 2 ms time windows for evidence of focal, planar, and colliding waveforms and the automated categorizations manually validated. Ten patients were recruited. A total of 360 s of data in 120 segments of 3 s from 60 left atrial locations were analyzed. RETRO‐map was highly effective at identifying focal waves and collisions during AF. PVI significantly reduced collision frequency but not focal and planar activation frequency. However, there was a significant reduction in the dispersion of activation directions. Larger studies may help determine factors associated with successful clinical outcome. [ABSTRACT FROM AUTHOR]

Background: The use of left bundle branch area pacing (LBBAP) for bradycardia pacing and cardiac resynchronization is increasing, but implants are not always successful. We prospectively studied consecutive patients to determine whether septal scar contributes to implant failure. Methods: Patients scheduled for bradycardia pacing or cardiac resynchronization therapy were prospectively enrolled. Recruited patients underwent preprocedural scar assessment by cardiac MRI with late gadolinium enhancement imaging. LBBAP was attempted using a lumenless lead (Medtronic 3830) via a transeptal approach. Results: Thirty‐five patients were recruited: 29 male, mean age 68 years, 10 ischemic, and 16 non‐ischemic cardiomyopathy. Pacing indication was bradycardia in 26% and cardiac resynchronization in 74%. The lead was successfully deployed to the left ventricular septum in 30/35 (86%) and unsuccessful in the remaining 5/35 (14%). Septal late gadolinium enhancement was significantly less extensive in patients where left septal lead deployment was successful, compared those where it was unsuccessful (median 8%, IQR 2%–18% vs. median 54%, IQR 53%–57%, p <.001). Conclusions: The presence of septal scar appears to make it more challenging to deploy a lead to the left ventricular septum via the transeptal route. Additional implant tools or alternative approaches may be required in patients with extensive septal scar. [ABSTRACT FROM AUTHOR]

[Figure: see text]. [ABSTRACT FROM AUTHOR]

Aims: Rate adaptation of the action potential ensures spatial heterogeneities in conduction across the myocardium are minimized at different heart rates providing a protective mechanism against ventricular fibrillation (VF) and sudden cardiac death (SCD), which can be quantified by the ventricular conduction stability (V-CoS) test previously described. We tested the hypothesis that patients with a history of aborted SCD due to an underlying channelopathy or cardiomyopathy have a reduced capacity to maintain uniform activation following exercise.Methods and Results: Sixty individuals, with (n = 28) and without (n = 32) previous aborted-SCD event underwent electro-cardiographic imaging recordings following exercise treadmill test. These included 25 Brugada syndrome, 13 hypertrophic cardiomyopathy, 12 idiopathic VF, and 10 healthy controls. Data were inputted into the V-CoS programme to calculate a V-CoS score that indicate the percentage of ventricle that showed no significant change in ventricular activation, with a lower score indicating the development of greater conduction heterogeneity. The SCD group, compared to those without, had a lower median (interquartile range) V-CoS score at peak exertion [92.8% (89.8-96.3%) vs. 97.3% (94.9-99.1%); P < 0.01] and 2 min into recovery [95.2% (91.1-97.2%) vs. 98.9% (96.9-99.5%); P < 0.01]. No significant difference was observable later into recovery at 5 or 10 min. Using the lowest median V-CoS scores obtained during the entire recovery period post-exertion, SCD survivors had a significantly lower score than those without for each of the different underlying aetiologies.Conclusion: Data from this pilot study demonstrate the potential use of this technique in risk stratification for the inherited cardiac conditions. [ABSTRACT FROM AUTHOR]

Background: Recent studies have demonstrated conflicting mechanisms underlying atrial fibrillation (AF), with the spatial resolution of data often cited as a potential reason for the disagreement. The purpose of this study was to investigate whether the variation in spatial resolution of mapping may lead to misinterpretation of the underlying mechanism in persistent AF.Methods and Results: Simulations of rotors and focal sources were performed to estimate the minimum number of recording points required to correctly identify the underlying AF mechanism. The effects of different data types (action potentials and unipolar or bipolar electrograms) and rotor stability on resolution requirements were investigated. We also determined the ability of clinically used endocardial catheters to identify AF mechanisms using clinically recorded and simulated data. The spatial resolution required for correct identification of rotors and focal sources is a linear function of spatial wavelength (the distance between wavefronts) of the arrhythmia. Rotor localization errors are larger for electrogram data than for action potential data. Stationary rotors are more reliably identified compared with meandering trajectories, for any given spatial resolution. All clinical high-resolution multipolar catheters are of sufficient resolution to accurately detect and track rotors when placed over the rotor core although the low-resolution basket catheter is prone to false detections and may incorrectly identify rotors that are not present.Conclusions: The spatial resolution of AF data can significantly affect the interpretation of the underlying AF mechanism. Therefore, the interpretation of human AF data must be taken in the context of the spatial resolution of the recordings. [ABSTRACT FROM AUTHOR]

Background: The activation pattern of localized reentry (LR) in atrial tachycardia remains incompletely understood. We used the ultra-high density Rhythmia mapping system to study activation patterns in LR.Methods and Results: LR was suggested by small rotatory activations (carousels) containing the full spectrum of the color-coded map. Twenty-three left-sided atrial tachycardias were mapped in 15 patients (age: 64±11 years). 16 253±9192 points were displayed per map, collected over 26±14 minutes. A total of 50 carousels were identified (median 2; quartiles 1-3 per map), although this represented LR in only n=7 out of 50 (14%): here, rotation occurred around a small area of scar (<0.03 mV; 12±6 mm diameter). In LR, electrograms along the carousel encompassed the full tachycardia cycle length, and surrounding activation moved away from the carousel in all directions. Ablating fractionated electrograms (117±18 ms; 44±13% of tachycardia cycle length) within the carousel interrupted the tachycardia in every LR case. All remaining carousels were pseudo-reentrant (n=43/50 [86%]) occurring in areas of wavefront collision (n=21; median 0.5; quartiles 0-2 per map) or as artifact because of annotation of noise or interpolation in areas of incomplete mapping (n=22; median 1, quartiles 0-2 per map). Pseudo-reentrant carousels were incorrectly ablated in 5 cases having been misinterpreted as LR.Conclusions: The activation pattern of LR is of small stable rotational activations (carousels), and this drove 30% (7/23) of our postablation atrial tachycardias. However, this appearance is most often pseudo-reentrant and must be differentiated by interpretation of electrograms in the candidate circuit and activation in the wider surrounding region. [ABSTRACT FROM AUTHOR]

Background: Post-infarct ventricular tachycardia is associated with channels of surviving myocardium within scar characterized by fractionated and low-amplitude signals usually occurring late during sinus rhythm. Conventional automated algorithms for 3-dimensional electro-anatomic mapping cannot differentiate the delayed local signal of conduction within the scar from the initial far-field signal generated by surrounding healthy tissue. Ripple mapping displays every deflection of an electrogram, thereby providing fully informative activation sequences. We prospectively used CARTO-based ripple maps to identify conducting channels as a target for ablation.Methods and Results: High-density bipolar left ventricular endocardial electrograms were collected using CARTO3v4 in sinus rhythm or ventricular pacing and reviewed for ripple mapping conducting channel identification. Fifteen consecutive patients (median age 68 years, left ventricular ejection fraction 30%) were studied (6 month preprocedural implantable cardioverter defibrillator therapies: median 19 ATP events [Q1-Q3=4-93] and 1 shock [Q1-Q3=0-3]). Scar (<1.5 mV) occupied a median 29% of the total surface area (median 540 points collected within scar). A median of 2 ripple mapping conducting channels were seen within each scar (length 60 mm; initial component 0.44 mV; delayed component 0.20 mV; conduction 55 cm/s). Ablation was performed along all identified ripple mapping conducting channels (median 18 lesions) and any presumed interconnected late-activating sites (median 6 lesions; Q1-Q3=2-12). The diastolic isthmus in ventricular tachycardia was mapped in 3 patients and colocated within the ripple mapping conducting channels identified. Ventricular tachycardia was noninducible in 85% of patients post ablation, and 71% remain free of ventricular tachycardia recurrence at 6-month median follow-up.Conclusions: Ripple mapping can be used to identify conduction channels within scar to guide functional substrate ablation. [ABSTRACT FROM AUTHOR]

Background Patients postpacemaker implant can undergo a full assessment by pacing system programmer (PSP) or a magnet check. The former takes longer, but provides more detailed information; a magnet-mode assessment is faster, but provides only capture data in an asynchronous pacing mode. A magnet-mode assessment alone may be sufficient in most cases, and current clinical practice varies considerably. Methods A retrospective single-center assessment of all pacemaker implants receiving PSP and magnet checks between September 2009 and April 2010. Patient records were reviewed. The results of PSP and magnet checks and any subsequent device-related management were noted. Results A total of 168 patients underwent pacemaker implantation, magnet-mode assessment, and then PSP interrogation during this period. Magnet-mode assessment revealed a problem in only one patient-failure of atrial capture, leading to subsequent atrial lead repositioning. None of the remaining 167 patients have a serious problem at PSP interrogation; six had minor issues at PSP check, none of which required repeat surgical intervention. Conclusions The magnet-mode test only provides information on lead capture in an asynchronous pacing mode, which is the most essential data postoperatively. Our study has suggested that a magnet-mode assessment without PSP interrogation may be sufficient in the immediate postimplant assessment of these patients. Routine postimplant PSP interrogation is time consuming, labor intensive, and adds only minimal additional benefit to the safe management of these patients above and beyond a magnet check, coupled with informed assessment of the associated electrocardiogram/rhythm strip, clinical examination, and chest x-ray. [ABSTRACT FROM AUTHOR]

Left Atrial Linear Cryoablation Background Left atrial linear lesions are part of the ablation strategy for persistent atrial fibrillation. Radiofrequency (RF) energy is the standard energy modality. Pulmonary vein (PV) balloon cryoablation has similar success rates to RF energy but is unsuitable for linear lesions. This study assessed the feasibility and safety of left atrial linear lesions using an 8 mm tip cryoablation catheter. Methods and Results Consecutive patients undergoing left atrial ablation procedures for paroxysmal or persistent atrial fibrillation were studied. An 8 mm tip focal cryoablation catheter was used to create mitral isthmus and left atrial roof linear lesions and compared to a matched cohort undergoing RF ablation. A total of 21 patients (54 ± 11 years, 14 male), 15 undergoing de novo procedures using a dual console technique (simultaneous focal catheter and cryoballoon PV ablation) and 6 redo procedures (single console and focal catheter) were studied. Mitral isthmus ablation was successful in 19/21 (91%) with a mean total ablation time of 32.5 ± 2.9 minutes. Roof line ablation was successful in 18/19 with a mean ablation time of 15.6 ± 6.0 minutes. Success rates were similar but ablation times were longer than those in the matched RF group. Epicardial ablation in the coronary sinus was required less often with cryoablation (11/21 vs 17/21, P < 0.05). There were no complications. Conclusion Left atrial linear lesions with an 8 mm tip cryoablation catheter are feasible and safe with a high acute success rate. The need for coronary sinus ablation is reduced. A dual console technique is possible. Long-term durability of linear lesions remains to be determined. [ABSTRACT FROM AUTHOR]