Effects of haemodynamically atrio-ventricular optimized His bundle pacing on heart failure symptoms and exercise capacity: the His Optimized Pacing Evaluated for Heart Failure (HOPE-HF) randomized, double-blind, cross-over trial.

AIMS: Excessive prolongation of PR interval impairs coupling of atrio-ventricular (AV) contraction, which reduces left ventricular pre-load and stroke volume, and worsens symptoms. His bundle pacing allows AV delay shortening while maintaining normal ventricular activation. HOPE-HF evaluated whether AV optimized His pacing is preferable to no-pacing, in a double-blind cross-over fashion, in patients with heart failure, left ventricular ejection fraction (LVEF) ≤40%, PR interval ≥200 ms and either QRS ≤140 ms or right bundle branch block. METHODS AND RESULTS: Patients had atrial and His bundle leads implanted (and an implantable cardioverter-defibrillator lead if clinically indicated) and were randomized to 6 months of pacing and 6 months of no-pacing utilizing a cross-over design. The primary outcome was peak oxygen uptake during symptom-limited exercise. Quality of life, LVEF and patients' holistic symptomatic preference between arms were secondary outcomes. Overall, 167 patients were randomized: 90% men, 69 ± 10 years, QRS duration 124 ± 26 ms, PR interval 249 ± 59 ms, LVEF 33 ± 9%. Neither peak oxygen uptake (+0.25 ml/kg/min, 95% confidence interval [CI] -0.23 to +0.73, p = 0.3) nor LVEF (+0.5%, 95% CI -0.7 to 1.6, p = 0.4) changed with pacing but Minnesota Living with Heart Failure quality of life improved significantly (-3.7, 95% CI -7.1 to -0.3, p = 0.03). Seventy-six percent of patients preferred His bundle pacing-on and 24% pacing-off (p < 0.0001). CONCLUSION: His bundle pacing did not increase peak oxygen uptake but, under double-blind conditions, significantly improved quality of life and was symptomatically preferred by the clear majority of patients. Ventricular pacing delivered via the His bundle did not adversely impact ventricular function during the 6 months.

A Multicenter External Validation of a Score Model to Predict Risk of Events in Patients With Brugada Syndrome.

A multivariate risk score model was proposed by Sieira et al in 2017 for sudden death in Brugada syndrome; their validation in 150 patients was highly encouraging, with a C-index of 0.81; however, this score is yet to be validated by an independent group. A total of 192 records of patients with Brugada syndrome were collected from 2 centers in the United Kingdom and retrospectively scored according to a score model by Sieira et al. Data were compiled summatively over follow-up to mimic regular risk re-evaluation as per current guidelines. Sudden cardiac death survivor data were considered perievent to ascertain the utility of the score before cardiac arrest. Scores were compared with actual outcomes. Sensitivity in our cohort was 22.7%, specificity was 57.6%, and C-index was 0.58. In conclusion, up to 75% of cardiac arrest survivors in this cohort would not have been offered a defibrillator if evaluated before their event. This casts doubt on the utility of the score model for primary prevention of sudden death. Inherent issues with modern risk scoring strategies decrease the likelihood of success even in robustly designed tools such as the Sieira score model.

Postinfarct ventricular tachycardia substrate: Characterization and ablation of conduction channels using ripple mapping.

BACKGROUND: Conduction channels have been demonstrated within the postinfarct scar and seem to be co-located with the isthmus of ventricular tachycardia (VT). Mapping the local scar potentials (SPs) that define the conduction channels is often hindered by large far-field electrograms generated by healthy myocardium. OBJECTIVE: The purpose of this study was to map conduction channel using ripple mapping to categorize SPs temporally and anatomically. We tested the hypothesis that ablation of early SPs would eliminate the latest SPs without direct ablation. METHODS: Ripple maps of postinfarct scar were collected using the PentaRay (Biosense Webster) during normal rhythm. Maps were reviewed in reverse, and clusters of SPs were color-coded on the geometry, by timing, into early, intermediate, late, and terminal. Ablation was delivered sequentially from clusters of early SPs, checking for loss of terminal SPs as the endpoint. RESULTS: The protocol was performed in 11 patients. Mean mapping time was 65 ± 23 minutes, and a mean 3050 ± 1839 points was collected. SP timing ranged from 98.1 ± 60.5 ms to 214.8 ± 89.8 ms post QRS peak. Earliest SPs were present at the border, occupying 16.4% of scar, whereas latest SPs occupied 4.8% at the opposing border or core. Analysis took 15 ± 10 minutes to locate channels and identify ablation targets. It was possible to eliminate latest SPs in all patients without direct ablation (mean ablation time 16.3 ± 11.1 minutes). No VT recurrence was recorded (mean follow-up 10.1 ± 7.4 months). CONCLUSION: Conduction channels can be located using ripple mapping to analyze SPs. Ablation at channel entrances can eliminate the latest SPs and is associated with good medium-term results.

Worldwide Survey of COVID-19-Associated Arrhythmias.

[Figure: see text].

Quantification of Electromechanical Coupling to Prevent Inappropriate Implantable Cardioverter-Defibrillator Shocks.

OBJECTIVES: This study sought to test specialized processing of laser Doppler signals for discriminating ventricular fibrillation (VF) from common causes of inappropriate therapies. BACKGROUND: Inappropriate implantable cardioverter-defibrillator (ICD) therapies remain a clinically important problem associated with morbidity and mortality. Tissue perfusion biomarkers, implemented to assist automated diagnosis of VF, sometimes mistake artifacts and random noise for perfusion, which could lead to shocks being inappropriately withheld. METHODS: The study tested a novel processing algorithm that combines electrogram data and laser Doppler perfusion monitoring as a method for assessing circulatory status. Fifty patients undergoing VF induction during ICD implantation were recruited. Noninvasive laser Doppler and continuous electrograms were recorded during both sinus rhythm and VF. Two additional scenarios that might have led to inappropriate shocks were simulated for each patient: ventricular lead fracture and T-wave oversensing. The laser Doppler was analyzed using 3 methods for reducing noise: 1) running mean; 2) oscillatory height; and 3) a novel quantification of electromechanical coupling which gates laser Doppler relative to electrograms. In addition, the algorithm was tested during exercise-induced sinus tachycardia. RESULTS: Only the electromechanical coupling algorithm found a clear perfusion cut off between sinus rhythm and VF (sensitivity and specificity of 100%). Sensitivity and specificity remained at 100% during simulated lead fracture and electrogram oversensing. (Area under the curve running mean: 0.91; oscillatory height: 0.86; electromechanical coupling: 1.00). Sinus tachycardia did not cause false positive results. CONCLUSIONS: Quantifying the coupling between electrical and perfusion signals increases reliability of discrimination between VF and artifacts that ICDs may interpret as VF. Incorporating such methods into future ICDs may safely permit reductions of inappropriate shocks.

Evaluation of a new algorithm for tracking activation during atrial fibrillation using multipolar catheters in humans.

BACKGROUND: Conventional mapping techniques during atrial fibrillation (AF) are difficult to apply because of cycle length irregularity. Mapping studies are usually restricted to short durations of AF in limited regions because of the laborious manual annotation of local activation time (LAT). The purpose of this study was to test an automated algorithm to map activation during AF, with comparable accuracy to manual annotation. METHODS: Left atrial (LA) mapping was performed using a 20-pole double loop catheter (AFocusII) in 30-second data segments from 16 patients. The new algorithm (RETRO-Mapping) was designed to detect wavefront propagation between electrodes, and display activating wavefronts on a two-dimensional representation of the catheter. Activation patterns were validated against their bipolar electrograms and with isochronal maps. The mapping protocol was approved by the research ethics committee (13/LO1169 and 14/LO1367). RESULTS: During AF, uniform wavefront activation direction (mean ± SD, degrees) from manually constructed isochronal maps was comparable to RETRO-Propagation Map (RETRO-PM) and RETRO-Automated Direction (RETRO-AD): 1 ± 6.9 for RETRO-PM; and 2 ± 6.6 for RETRO-AD. There was no significant difference in activation direction assigned to 1373 uniform wavefronts during AF when comparing RETRO-PM with RETRO-AD (Bland-Altman mean difference: -0.1 degrees; limits of agreement: -8.0 to 8.3; 95% CI -0.4 to 0.2; (r = 0.01) R2 = < 0.005; P = .77). CONCLUSION: We have developed and validated a new technique to map activation during AF. This technique shows comparable accuracy to that of conventional isochronal mapping with careful manual adjustment of LAT.

Voltage during atrial fibrillation is superior to voltage during sinus rhythm in localizing areas of delayed enhancement on magnetic resonance imaging: An assessment of the posterior left atrium in patients with persistent atrial fibrillation.

BACKGROUND: Bipolar electrogram voltage during sinus rhythm (VSR) has been used as a surrogate for atrial fibrosis in guiding catheter ablation of persistent atrial fibrillation (AF), but the fixed rate and wavefront characteristics present during sinus rhythm may not accurately reflect underlying functional vulnerabilities responsible for AF maintenance. OBJECTIVE: The purpose of this study was determine whether, given adequate temporal sampling, the spatial distribution of mean AF voltage (VmAF) better correlates with delayed-enhancement magnetic resonance imaging (MRI-DE)-detected atrial fibrosis than VSR. METHODS: AF was mapped (8 seconds) during index ablation for persistent AF (20 patients) using a 20-pole catheter (660 ± 28 points/map). After cardioversion, VSR was mapped (557 ± 326 points/map). Electroanatomic and MRI-DE maps were co-registered in 14 patients. RESULTS: The time course of VmAF was assessed from 1-40 AF cycles (∼8 seconds) at 1113 locations. VmAF stabilized with sampling >4 seconds (mean voltage error 0.05 mV). Paired point analysis of VmAF from segments acquired 30 seconds apart (3667 sites; 15 patients) showed strong correlation (r = 0.95; P <.001). Delayed enhancement (DE) was assessed across the posterior left atrial (LA) wall, occupying 33% ± 13%. VmAF distributions were (median [IQR]) 0.21 [0.14-0.35] mV in DE vs 0.52 [0.34-0.77] mV in non-DE regions. VSR distributions were 1.34 [0.65-2.48] mV in DE vs 2.37 [1.27-3.97] mV in non-DE. VmAF threshold of 0.35 mV yielded sensitivity of 75% and specificity of 79% in detecting MRI-DE compared with 63% and 67%, respectively, for VSR (1.8-mV threshold). CONCLUSION: The correlation between low-voltage and posterior LA MRI-DE is significantly improved when acquired during AF vs sinus rhythm. With adequate sampling, mean AF voltage is a reproducible marker reflecting the functional response to the underlying persistent AF substrate.

Optimum lesion set and predictors of outcome in persistent atrial fibrillation ablation: a meta-regression analysis.

AIMS: Ablation of persistent atrial fibrillation (PsAF) has been performed by many techniques with varying success rates. This may be due to ablation techniques, patient demographics, comorbidities, and trial design. We conducted a meta-regression of studies of PsAF ablation to elucidate the factors affecting atrial fibrillation (AF) recurrence. METHODS AND RESULTS: Databases were searched for prospective studies of PsAF ablation. A meta-regression was performed. Fifty-eight studies (6767 patients) were included. Complex fractionated atrial electrogram (CFAE) ablation reduced freedom from AF by 8.9% [95% confidence interval (CI) -15 to -2.3, P = 0.009). Left atrial appendage [LAA isolation (three study arms)] increased freedom from AF by 39.5% (95% CI 9.1-78.4, P = 0.008). Posterior wall isolation (PWI) (eight study arms) increased freedom from AF by 19.4% (95% CI 3.3-38.1, P = 0.017). Linear ablation or ganglionated plexi ablation resulted in no significant effect on freedom from AF. More extensive ablation increased intraprocedural AF termination; however, intraprocedural AF termination was not associated with improved outcomes. Increased left atrial diameter was associated with a reduction in freedom from AF by 4% (95% CI -6.8% to -1.1%, P = 0.007) for every 1 mm increase in diameter. CONCLUSION: Linear ablation, PWI, and CFAE ablation improves intraprocedural AF termination, but such termination does not predict better long-term outcomes. Study arms including PWI or LAA isolation in the lesion set were associated with improved outcomes in terms of freedom from AF; however, further randomized trials are required before these can be routinely recommended. Left atrial size is the most important marker of AF chronicity influencing outcomes.

Isthmus sites identified by Ripple Mapping are usually anatomically stable: A novel method to guide atrial substrate ablation?

BACKGROUND: Postablation reentrant ATs depend upon conducting isthmuses bordered by scar. Bipolar voltage maps highlight scar as sites of low voltage, but the voltage amplitude of an electrogram depends upon the myocardial activation sequence. Furthermore, a voltage threshold that defines atrial scar is unknown. We used Ripple Mapping (RM) to test whether these isthmuses were anatomically fixed between different activation vectors and atrial rates. METHODS: We studied post-AF ablation ATs where >1 rhythm was mapped. Multipolar catheters were used with CARTO Confidense for high-density mapping. RM visualized the pattern of activation, and the voltage threshold below which no activation was seen. Isthmuses were characterized at this threshold between maps for each patient. RESULTS: Ten patients were studied (Map 1 was AT1; Map 2: sinus 1/10, LA paced 2/10, AT2 with reverse CS activation 3/10; AT2 CL difference 50 ± 30 ms). Point density was similar between maps (Map 1: 2,589 ± 1,330; Map 2: 2,214 ± 1,384; P  =  0.31). RM activation threshold was 0.16 ± 0.08 mV. Thirty-one isthmuses were identified in Map 1 (median 3 per map; width 27 ± 15 mm; 7 anterior; 6 roof; 8 mitral; 9 septal; 1 posterior). Importantly, 7 of 31 (23%) isthmuses were unexpectedly identified within regions without prior ablation. AT1 was treated following ablation of 11/31 (35%) isthmuses. Of the remaining 20 isthmuses, 14 of 16 isthmuses (88%) were consistent between the two maps (four were inadequately mapped). Wavefront collision caused variation in low voltage distribution in 2 of 16 (12%). CONCLUSIONS: The distribution of isthmuses and nonconducting tissue within the ablated left atrium, as defined by RM, appear concordant between rhythms. This could guide a substrate ablative approach.

Repolarization abnormalities unmasked with exercise in sudden cardiac death survivors with structurally normal hearts.

BACKGROUND: Models of cardiac arrhythmogenesis predict that nonuniformity in repolarization and/or depolarization promotes ventricular fibrillation and is modulated by autonomic tone, but this is difficult to evaluate in patients. We hypothesize that such spatial heterogeneities would be detected by noninvasive ECG imaging (ECGi) in sudden cardiac death (SCD) survivors with structurally normal hearts under physiological stress. METHODS: ECGi was applied to 11 SCD survivors, 10 low-risk Brugada syndrome patients (BrS), and 10 controls undergoing exercise treadmill testing. ECGi provides whole heart activation maps and >1,200 unipolar electrograms over the ventricular surface from which global dispersion of activation recovery interval (ARI) and regional delay in conduction were determined. These were used as surrogates for spatial heterogeneities in repolarization and depolarization. Surface ECG markers of dispersion (QT and Tpeak-end intervals) were also calculated for all patients for comparison. RESULTS: Following exertion, the SCD group demonstrated the largest increase in ARI dispersion compared to BrS and control groups (13 ± 8 ms vs. 4 ± 7 ms vs. 4 ± 5 ms; P = 0.009), with baseline dispersion being similar in all groups. In comparison, surface ECG markers of dispersion of repolarization were unable to discriminate between the groups at baseline or following exertion. Spatial heterogeneities in conduction were also present following exercise but were not significantly different between SCD survivors and the other groups. CONCLUSION: Increased dispersion of repolarization is apparent during physiological stress in SCD survivors and is detectable with ECGi but not with standard ECG parameters. The electrophysiological substrate revealed by ECGi could be the basis of alternative risk-stratification techniques.

Ripple mapping: Initial multicenter experience of an intuitive approach to overcoming the limitations of 3D activation mapping.

BACKGROUND: Ripple mapping (RM) displays electrograms as moving bars over a three-dimensional surface displaying bipolar voltage, and has shown in a single-center series to be effective for atrial tachycardia (AT) mapping without annotation of local activation time or window-of-interest assignment. We tested the reproducibility of these findings in operators naïve to RM, using it for the first time in postablation AT. METHODS: Maps were collected with multielectrode catheters and CARTO ConfiDENSE. A diagnosis of the tachycardia mechanism was made using RM and an assessment of operator confidence was made according to a three-grade scale (1 highest-3 lowest). RESULTS: The first 20 patients (64 ± 9 years, median two previous ablations) undergoing RM-guided AT ablation across five sites were studied. High-density maps (2,935 ± 1,328 points) in AT (CL = 296 ± 95 milliseconds) were collected. Macroreentrant ATs bordered by scar or anatomical obstacles were identified in n = 12 (60%), small reentrant ATs around scar in n = 3 (15%), and focal ATs from scar in n = 5 (25%). Diagnostic confidence with RM was grade 1 in n = 13 (65%), where operators felt confident to proceed to ablation without entrainment. Ablation offered the correct diagnosis n = 18 (90%). Retrospective review of the accompanying LAT maps demonstrated potential sources for error related to the window of interest selection, interpolation, and differentiating regions of scar during tachycardia on the voltage map. CONCLUSION: RM was easy to adopt by operators using it for the first time, and identified the correct target for ablation with high diagnostic confidence in most cases of complex AT.

Spatial Resolution Requirements for Accurate Identification of Drivers of Atrial Fibrillation.

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.

Characterization and consistency of interactions of triggers and substrate at the onset of paroxysmal atrial fibrillation.

AIMS: Initiating mechanisms of atrial fibrillation (AF) remain poorly understood, involving complex interaction between triggers and the atrial substrate. This study sought to classify the transitional phenomena, hypothesizing that there is consistency within and between patients in trigger-substrate interaction during transition to AF. METHODS AND RESULTS: Non-contact left atrial (LA) mapping was performed in 17 patients undergoing ablation for paroxysmal AF. All had spontaneous ectopy. Left atrial activation from the first ectopic to established AF was examined offline to characterize the initiating and transitional sequence of activation. In 57 fully mapped spontaneous AF initiations in 8 patients, all involved interaction of pulmonary venous/LA triggers with a septopulmonary line of block (SP-LOB) also evident in sinus rhythm, by 4 different transitional mechanisms characterized by (i) continuous focal firing: AF resulted from fragmentation of each ectopic wavefront through gaps in the SP-LOB and persisted only while focal firing continued (n = 18/32%) (ii) transient focal firing, wavefront fragmentation at the SP-LOB produced wavelet re-entry that persisted after cessation of an initiating ectopic source (n = 12/21%), (iii) of two separate interacting ectopic foci (n = 15/26%), or from (iv) transiently stable macroreentry (n = 12/21%), around the SP-LOB extending to the LA roof, resulting in progressive wavefront fragmentation. It was found that 79 ± 22% of each of the initiations in individual patients showed the same triggering mechanism. CONCLUSION: Onset of paroxysmal AF can be described by discrete mechanistic categories, all involving interaction of ectopic activity with a common SP-LOB. Within/between-patient consistency of initiations suggests constancy of the interacting triggers and substrate, and supports the concept of mechanistically tailored treatment.

A Prospective Study of Ripple Mapping the Post-Infarct Ventricular Scar to Guide Substrate Ablation for Ventricular Tachycardia.

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.

A Prospective Study of Ripple Mapping in Atrial Tachycardias: A Novel Approach to Interpreting Activation in Low-Voltage Areas.

BACKGROUND: Post ablation atrial tachycardias are characterized by low-voltage signals that challenge current mapping methods. Ripple mapping (RM) displays every electrogram deflection as a bar moving from the cardiac surface, resulting in the impression of propagating wavefronts when a series of bars move consecutively. RM displays fractionated signals in their entirety thereby helping to identify propagating activation in low-voltage areas from nonconducting tissue. We prospectively used RM to study tachycardia activation in the previously ablated left atrium. METHODS AND RESULTS: Patients referred for atrial tachycardia ablation underwent dense electroanatomic point collection using CARTO3v4. RM was played over a bipolar voltage map and used to determine the voltage "activation threshold" that differentiated functional low voltage from nonconducting areas for each map. Ablation was guided by RM, but operators could perform entrainment or review the isochronal activation map for diagnostic uncertainty. Twenty patients were studied. Median RM determined activation threshold was 0.3 mV (0.19-0.33), with nonconducting tissue covering 33±9% of the mapped surface. All tachycardias crossed an isthmus (median, 0.52 mV, 13 mm) bordered by nonconducting tissue (70%) or had a breakout source (median, 0.35 mV) moving away from nonconducting tissue (30%). In reentrant circuits (14/20) the path length was measured (87-202 mm), with 9 of 14 also supporting a bystander circuit (path lengths, 147-234 mm). In breakout tachycardias, splitting of wavefronts resulted in 2 to 4 incomplete circuits. RM-guided ablation interrupted the tachycardia in 19 of 20 cases with the first ablation set. CONCLUSIONS: RM helps to define activation through low-voltage regions and aids ablation of atrial tachycardias.

A diagnostic algorithm to optimize data collection and interpretation of Ripple Maps in atrial tachycardias.

BACKGROUND: Ripple Mapping (RM) is designed to overcome the limitations of existing isochronal 3D mapping systems by representing the intracardiac electrogram as a dynamic bar on a surface bipolar voltage map that changes in height according to the electrogram voltage-time relationship, relative to a fiduciary point. OBJECTIVE: We tested the hypothesis that standard approaches to atrial tachycardia CARTO™ activation maps were inadequate for RM creation and interpretation. From the results, we aimed to develop an algorithm to optimize RMs for future prospective testing on a clinical RM platform. METHODS: CARTO-XP™ activation maps from atrial tachycardia ablations were reviewed by two blinded assessors on an off-line RM workstation. Ripple Maps were graded according to a diagnostic confidence scale (Grade I - high confidence with clear pattern of activation through to Grade IV - non-diagnostic). The RM-based diagnoses were corroborated against the clinical diagnoses. RESULTS: 43 RMs from 14 patients were classified as Grade I (5 [11.5%]); Grade II (17 [39.5%]); Grade III (9 [21%]) and Grade IV (12 [28%]). Causes of low gradings/errors included the following: insufficient chamber point density; window-of-interest<100% of cycle length (CL); <95% tachycardia CL mapped; variability of CL and/or unstable fiducial reference marker; and suboptimal bar height and scar settings. CONCLUSIONS: A data collection and map interpretation algorithm has been developed to optimize Ripple Maps in atrial tachycardias. This algorithm requires prospective testing on a real-time clinical platform.

Evidence that conflict regarding size of haemodynamic response to interventricular delay optimization of cardiac resynchronization therapy may arise from differences in how atrioventricular delay is kept constant.

AIMS: Whether adjusting interventricular (VV) delay changes haemodynamic efficacy of cardiac resynchronization therapy (CRT) is controversial, with conflicting results. This study addresses whether the convention for keeping atrioventricular (AV) delay constant during VV optimization might explain these conflicts. METHOD AND RESULTS: Twenty-two patients in sinus rhythm with existing CRT underwent VV optimization using non-invasive systolic blood pressure. Interventricular optimization was performed with four methods for keeping the AV delay constant: (i) atrium and left ventricle delay kept constant, (ii) atrium and right ventricle delay kept constant, (iii) time to the first-activated ventricle kept constant, and (iv) time to the second-activated ventricle kept constant. In 11 patients this was performed with AV delay of 120 ms, and in 11 at AV optimum. At AV 120 ms, time to the first ventricular lead (left or right) was the overwhelming determinant of haemodynamics (13.75 mmHg at ±80 ms, P < 0.001) with no significant effect of time to second lead (0.47 mmHg, P = 0.50), P < 0.001 for difference. At AV optimum, time to first ventricular lead again had a larger effect (5.03 mmHg, P < 0.001) than time to second (2.92 mmHg, P = 0.001), P = 0.02 for difference. CONCLUSION: Time to first ventricular activation is the overwhelming determinant of circulatory function, regardless of whether this is the left or right ventricular lead. If this is kept constant, the effect of changing time to the second ventricle is small or nil, and is not beneficial. In practice, it may be advisable to leave VV delay at zero. Specifying how AV delay is kept fixed might make future VV delay research more enlightening.

Focal Arrhythmia Ablation Determined by High-Resolution Noninvasive Maps: Multicenter Feasibility Study.

INTRODUCTION: A noninvasive 3D mapping technique (ECVUE™, CardioInsight Inc., Cleveland) maps the origin and mechanisms of various arrhythmias without catheterizing the heart. METHODS: Thirty-three patients (3 centers, mean 45.0 ± 14.6 years,) with symptomatic premature ventricular complexes (24 PVCs), focal atrial tachycardias (2 ATs), and manifest accessory pathways (7 WPW syndromes) were prospectively explored using 3D, noninvasive bedside electrocardiomapping. The location of origin of the focal arrhythmia was first determined using noninvasive mapping. Subsequently, a stimulus artifact was delivered at this site to confirm and evaluate the precise location of the mapped focal origin. The procedural parameters and clinical efficacy were studied. RESULTS: Ablation was successful in 32/33 (97%) patients (PVCs: 13 right, 10 left, 1 septal; WPW: 3 left, 3 right; ATs: 2 left) without complications. The time from catheterization to permanent arrhythmia elimination/termination, RF duration, skin-to-skin procedural duration, and fluoroscopic exposure were median 16, 3.98, 71, and 11.9 minutes (for n = 29), respectively. At mean 24.7 ± 3.7 months of follow-up, 31 patients remain arrhythmia-free after a single procedure. One patient (right WPW syndrome) required repeat ablation 1 month later. One patient had recurrence of PVCs and is now deceased. The cumulative radiation (CT scan and fluoroscopy) exposure was median 7.57 mSv. CONCLUSION: ECVUE(TM) is a noninvasive tool allowing rapid preprocedural localization of focal arrhythmia and enables the electrophysiologist with highly specific information to direct RF delivery at the source of the arrhythmia with minimal intracardiac mapping.