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Aims: The randomized, double‐blind, placebo‐controlled HOPE‐HF trial assessed the benefit of atrio‐ventricular (AV) delay optimization delivered using His bundle pacing. It recruited patients with left ventricular ejection fraction ≤40%, PR interval ≥200 ms, and baseline QRS ≤140 ms or right bundle branch block. Overall, there was no significant increase in peak oxygen uptake (VO2max) but there was significant improvement in heart failure specific quality of life. In this pre‐specified secondary analysis, we evaluated the impact of baseline PR interval, echocardiographic E‐A fusion, and the magnitude of acute high‐precision haemodynamic response to pacing, on outcomes. Methods and results: All 167 randomized participants underwent measurement of PR interval, acute haemodynamic response at optimized AV delay, and assessment of presence of E‐A fusion. We tested the impact of these baseline parameters using a Bayesian ordinal model on VO2max, quality of life and activity measures. There was strong evidence of a beneficial interaction between the baseline acute haemodynamic response and the blinded benefit of pacing for VO2 (Pr 99.9%), Minnesota Living With Heart Failure (MLWHF) (Pr 99.8%), MLWHF physical limitation score (Pr 98.9%), EQ‐5D visual analogue scale (Pr 99.6%), and exercise time (Pr 99.4%). The baseline PR interval and the presence of baseline E‐A fusion did not have this reliable ability to predict the clinical benefit of pacing over placebo across multiple endpoints. Conclusions: In the HOPE‐HF trial, the acute haemodynamic response to pacing reliably identified patients who obtained clinical benefit. Patients with a long PR interval (≥200 ms) and left ventricular impairment who obtained acute haemodynamic improvement with AV‐optimized His bundle pacing were likely to obtain clinical benefit, consistent across multiple endpoints. Importantly, this gradation can be reliably tested for before randomization, but does require high‐precision AV‐optimized haemodynamic assessment to be performed. [ABSTRACT FROM AUTHOR]

Background: Ventricular tachycardia (VT) reduces cardiac output through high heart rates, loss of atrioventricular synchrony, and loss of ventricular synchrony. We studied the contribution of each mechanism and explored the potential therapeutic utility of His bundle pacing to improve cardiac output during VT. Methods: Study 1 aimed to improve the understanding of mechanisms of harm during VT (using pacing simulated VT). In 23 patients with left ventricular impairment, we recorded continuous ECG and beat-by-beat blood pressure measurements. We assessed the hemodynamic impact of heart rate and restoration of atrial and biventricular synchrony. Study 2 investigated novel pacing interventions during clinical VT by evaluating the hemodynamic effects of His bundle pacing at 5 bpm above the VT rate in 10 patients. Results: In Study 1, at progressively higher rates of simulated VT, systolic blood pressure declined: at rates of 125, 160, and 190 bpm, -22.2%, -42.0%, and -58.7%, respectively (ANOVA p < 0.0001). Restoring atrial synchrony alone had only a modest beneficial effect on systolic blood pressure (+ 3.6% at 160 bpm, p = 0.2117), restoring biventricular synchrony alone had a greater effect (+ 9.1% at 160 bpm, p = 0.242), and simultaneously restoring both significantly increased systolic blood pressure (+ 31.6% at 160 bpm, p = 0.0003). In Study 2, the mean rate of clinical VT was 143 ± 21 bpm. His bundle pacing increased systolic blood pressure by + 14.2% (p = 0.0023). In 6 of 10 patients, VT terminated with His bundle pacing. Conclusions: Restoring atrial and biventricular synchrony improved hemodynamic function in simulated and clinical VT. Conduction system pacing could improve VT tolerability and treatment. [ABSTRACT FROM AUTHOR]

Introduction: Patients with hypertrophic cardiomyopathy (HCM) are at risk for lethal ventricular arrhythmia, but the electrophysiological substrate behind this is not well-understood. We used non-invasive electrocardiographic imaging to characterize patients with HCM, including cardiac arrest survivors. Methods: HCM patients surviving ventricular fibrillation or hemodynamically unstable ventricular tachycardia (n = 17) were compared to HCM patients without a personal history of potentially lethal arrhythmia (n = 20) and a pooled control group with structurally normal hearts. Subjects underwent exercise testing by non-invasive electrocardiographic imaging to estimate epicardial electrophysiology. Results: Visual inspection of reconstructed epicardial HCM maps revealed isolated patches of late activation time (AT), prolonged activation-recovery intervals (ARIs), as well as reversal of apico-basal trends in T-wave inversion and ARI compared to controls (p < 0.005 for all). AT and ARI were compared between groups. The pooled HCM group had longer mean AT (60.1 ms vs. 52.2 ms, p < 0.001), activation dispersion (55.2 ms vs. 48.6 ms, p = 0.026), and mean ARI (227 ms vs. 217 ms, p = 0.016) than structurally normal heart controls. HCM ventricular arrhythmia survivors could be differentiated from HCM patients without a personal history of life-threatening arrhythmia by longer mean AT (63.2 ms vs. 57.4 ms, p = 0.007), steeper activation gradients (0.45 ms/mm vs. 0.36 ms/mm, p = 0.011), and longer mean ARI (234.0 ms vs. 221.4 ms, p = 0.026). A logistic regression model including whole heart mean activation time and activation recovery interval could identify ventricular arrhythmia survivors from the HCM cohort, producing a C statistic of 0.76 (95% confidence interval 0.72-0.81), with an optimal sensitivity of 78.6% and a specificity of 79.8%. Discussion: The HCM epicardial electrotype is characterized by delayed, dispersed conduction and prolonged, dispersed activation-recovery intervals. Combination of electrophysiologic measures with logistic regression can improve differentiation over single variables. Future studies could test such models prospectively for risk stratification of sudden death due to HCM. [ABSTRACT FROM AUTHOR]

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: Patients with atrial fibrillation (AF) and likelihood of bleeding can undergo left atrial appendage occlusion (LAAO) as an alternative method of stroke prophylaxis. Short‐term anti‐thrombotic drugs are used postprocedure to offset the risk of device‐related thrombus, evidence for this practice is limited. Objectives: To investigate optimal postimplant antithrombotic strategy in high bleeding‐risk patients. Methods: Patients with AF and high‐risk for both stroke and bleeding undergoing LAAO were advised their perioperative drug therapy by a multidisciplinary physician panel. Those deemed to be at higher risk of bleeding from anti‐thrombotic drugs were assigned to minimal treatment with no antithrombotics or Aspirin‐alone. The remaining patients received standard care (STG) with a 12 week course of dual‐antiplatelets or anticoagulation postimplant. We compared mortality, device‐related thrombus, ischemic stroke, and bleeding events during the 90 days postimplant and long‐term. Event‐free survival was assessed using Kaplan−Meier survival analysis, with logrank testing for statistical significance. Results: Seventy‐five patients underwent LAAO of whom 63 patients (84%) had a prior serious bleeding event. The 42 patients on minimal treatment were older (74.3 ± 7.7 vs. 71.2 ± 7.2) with higher HASBLED score (3.6 ± 0.9 vs. 3.3 ± 1.2) than the 33 patients having standard care. There were no device‐related thrombi or strokes in either group at 90 days postprocedure; STG had more bleeding events (5/33 vs. 0/42, p = 0.01) with associated deaths (3/33 vs. 0/42, p = 0.05). During long‐term follow‐up (median 2.2 years), all patients transitioned onto no antithrombotic drugs (43 patients [61%]) or a single‐antiplatelet (29 patients [39%]). There was no evidence of early minimal treatment adversely affecting long‐term outcomes. Conclusions: Short‐term anti‐thrombotic drugs may not be needed after LAAO implant in patients with high bleeding risk and could be harmful. Larger, prospective studies would be warranted to test these findings. [ABSTRACT FROM AUTHOR]

Aims Left bundle branch pacing (LBBP) can deliver physiological left ventricular activation, but typically at the cost of delayed right ventricular (RV) activation. Right ventricular activation can be advanced through anodal capture, but there is uncertainty regarding the mechanism by which this is achieved, and it is not known whether this produces haemodynamic benefit. Methods and results We recruited patients with LBBP leads in whom anodal capture eliminated the terminal R -wave in lead V1. Ventricular activation pattern, timing, and high-precision acute haemodynamic response were studied during LBBP with and without anodal capture. We recruited 21 patients with a mean age of 67 years, of whom 14 were males. We measured electrocardiogram timings and haemodynamics in all patients, and in 16, we also performed non-invasive mapping. Ventricular epicardial propagation maps demonstrated that RV septal myocardial capture, rather than right bundle capture, was the mechanism for earlier RV activation. With anodal capture, QRS duration and total ventricular activation times were shorter (116 ± 12 vs. 129 ± 14 ms, P < 0.01 and 83 ± 18 vs. 90 ± 15 ms, P = 0.01). This required higher outputs (3.6 ± 1.9 vs. 0.6 ± 0.2 V, P < 0.01) but without additional haemodynamic benefit (mean difference −0.2 ± 3.8 mmHg compared with pacing without anodal capture, P = 0.2). Conclusion Left bundle branch pacing with anodal capture advances RV activation by stimulating the RV septal myocardium. However, this requires higher outputs and does not improve acute haemodynamics. Aiming for anodal capture may therefore not be necessary. [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]

Aims Left bundle branch area pacing (LBBAP) is a promising method for delivering cardiac resynchronization therapy (CRT), but its relative physiological effectiveness compared with His bundle pacing (HBP) is unknown. We conducted a within-patient comparison of HBP, LBBAP, and biventricular pacing (BVP). Methods and results Patients referred for CRT were recruited. We assessed electrical response using non-invasive mapping, and acute haemodynamic response using a high-precision haemodynamic protocol. Nineteen patients were recruited: 14 male, mean LVEF of 30%. Twelve had time for BVP measurements. All three modalities reduced total ventricular activation time (TVAT), (ΔTVATHBP -43 ± 14 ms and ΔTVATLBBAP −35 ± 20 ms vs. ΔTVATBVP −19 ± 30 ms, P = 0.03 and P = 0.1, respectively). HBP produced a significantly greater reduction in TVAT compared with LBBAP in all 19 patients (−46 ± 15 ms, −36 ± 17 ms, P = 0.03). His bundle pacing and LBBAP reduced left ventricular activation time (LVAT) more than BVP (ΔLVATHBP −43 ± 16 ms, P < 0.01 vs. BVP, ΔLVATLBBAP −45 ± 17 ms, P < 0.01 vs. BVP, ΔLVATBVP −13 ± 36 ms), with no difference between HBP and LBBAP (P = 0.65). Acute systolic blood pressure was increased by all three modalities. In the 12 with BVP, greater improvement was seen with HBP and LBBAP (6.4 ± 3.8 mmHg BVP, 8.1 ± 3.8 mmHg HBP, P = 0.02 vs. BVP and 8.4 ± 8.2 mmHg for LBBAP, P = 0.3 vs. BVP), with no difference between HBP and LBBAP (P = 0.8). Conclusion HBP delivered better ventricular resynchronization than LBBAP because right ventricular activation was slower during LBBAP. But LBBAP was not inferior to HBP with respect to LV electrical resynchronization and acute haemodynamic response. [ABSTRACT FROM AUTHOR]

Aims: Excessive prolongation of PR interval impairs coupling of 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 double-blind cross-over fashion, in patients with heart failure, left ventricular ejection fraction (LVEF) ≤40%, PR interval ≥200ms and either QRS ≤140ms or right BBB.Methods and Results: Patients had atrial and His-bundle leads implanted (and an ICD 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. 167 patients were randomized: 90% men, 69±10 years, QRS duration 124±26ms, PR interval 249±59ms, LVEF 33±9%. Neither peak VO2 (+0.25 ml/min/kg, 95% 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). 76% 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. This article is protected by copyright. All rights reserved. [ABSTRACT FROM AUTHOR]

Purpose: Left atrial (LA) rapid AF activity has been shown to co-localise with areas of successful atrial fibrillation termination by catheter ablation. We describe a technique that identifies rapid and regular activity. Methods: Eight-second AF electrograms were recorded from LA regions during ablation for psAF. Local activation was annotated manually on bipolar signals and where these were of poor quality, we inspected unipolar signals. Dominant cycle length (DCL) was calculated from annotation pairs representing a single activation interval, using a probability density function (PDF) with kernel density estimation. Cumulative annotation duration compared to total segment length defined electrogram quality. DCL results were compared to dominant frequency (DF) and averaging. Results: In total 507 8 s AF segments were analysed from 7 patients. Spearman's correlation coefficient was 0.758 between independent annotators (P < 0.001), 0.837–0.94 between 8 s and ≥ 4 s segments (P < 0.001), 0.541 between DCL and DF (P < 0.001), and 0.79 between DCL and averaging (P < 0.001). Poorer segment organization gave greater errors between DCL and DF. Conclusion: DCL identifies rapid atrial activity that may represent psAF drivers. This study uses DCL as a tool to evaluate the dynamic, patient specific properties of psAF by identifying rapid and regular activity. If automated, this technique could rapidly identify areas for ablation in psAF. [ABSTRACT FROM AUTHOR]

Background: Atrial fibrillation (AF) and ventricular fibrillation (VF) are complex heart rhythm disorders and may be sustained by distinct electrophysiological mechanisms. Disorganised self-perpetuating multiple-wavelets and organised rotational drivers (RDs) localising to specific areas are both possible mechanisms by which fibrillation is sustained. Determining the underlying mechanisms of fibrillation may be helpful in tailoring treatment strategies. We investigated whether global fibrillation organisation, a surrogate for fibrillation mechanism, can be determined from electrocardiograms (ECGs) using band-power (BP) feature analysis and machine learning. Methods: In this study, we proposed a novel ECG classification framework to differentiate fibrillation organisation levels. BP features were derived from surface ECGs and fed to a linear discriminant analysis classifier to predict fibrillation organisation level. Two datasets, single-channel ECGs of rat VF (n = 9) and 12-lead ECGs of human AF (n = 17), were used for model evaluation in a leave-one-out (LOO) manner. Results: The proposed method correctly predicted the organisation level from rat VF ECG with the sensitivity of 75%, specificity of 80%, and accuracy of 78%, and from clinical AF ECG with the sensitivity of 80%, specificity of 92%, and accuracy of 88%. Conclusion: Our proposed method can distinguish between AF/VF of different global organisation levels non-invasively from the ECG alone. This may aid in patient selection and guiding mechanism-directed tailored treatment strategies. [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: His bundle pacing (HBP) is an alternative to biventricular pacing (BVP) for delivering cardiac resynchronization therapy (CRT) in patients with heart failure and left bundle branch block (LBBB). It is not known whether ventricular activation times and patterns achieved by HBP are equivalent to intact conduction systems and not all patients with LBBB are resynchronized by HBP. Objective: To compare activation times and patterns of His‐CRT with BVP‐CRT, LBBB and intact conduction systems. Methods: In patients with LBBB, noninvasive epicardial mapping (ECG imaging) was performed during BVP and temporary HBP. Intrinsic activation was mapped in all subjects. Left ventricular activation times (LVAT) were measured and epicardial propagation mapping (EPM) was performed, to visualize epicardial wavefronts. Normal activation pattern and a normal LVAT range were determined from normal subjects. Results: Forty‐five patients were included, 24 with LBBB and LV impairment, and 21 with normal 12‐lead ECG and LV function. In 87.5% of patients with LBBB, His‐CRT successfully shortened LVAT by ≥10 ms. In 33.3%, His‐CRT resulted in complete ventricular resynchronization, with activation times and patterns indistinguishable from normal subjects. EPM identified propagation discontinuity artifacts in 83% of patients with LBBB. This was the best predictor of whether successful resynchronization was achieved by HBP (logarithmic odds ratio, 2.19; 95% confidence interval, 0.07–4.31; p =.04). Conclusion: Noninvasive electrocardiographic mapping appears to identify patients whose LBBB can be resynchronized by HBP. In contrast to BVP, His‐CRT may deliver the maximum potential ventricular resynchronization, returning activation times, and patterns to those seen in normal hearts. [ABSTRACT FROM AUTHOR]

Background: Conduction velocity (CV) heterogeneity and myocardial fibrosis both promote re-entry, but the relationship between fibrosis as determined by left atrial (LA) late-gadolinium enhanced cardiac magnetic resonance imaging (LGE-CMRI) and CV remains uncertain. Objective: Although average CV has been shown to correlate with regional LGE-CMRI in patients with persistent AF, we test the hypothesis that a localized relationship exists to underpin LGE-CMRI as a minimally invasive tool to map myocardial conduction properties for risk stratification and treatment guidance. Method: 3D LA electroanatomic maps during LA pacing were acquired from eight patients with persistent AF following electrical cardioversion. Local CVs were computed using triads of concurrently acquired electrograms and were co-registered to allow correlation with LA wall intensities obtained from LGE-CMRI, quantified using normalized intensity (NI) and image intensity ratio (IIR). Association was evaluated using multilevel linear regression. Results: An association between CV and LGE-CMRI intensity was observed at scales comparable to the size of a mapping electrode: −0.11 m/s per unit increase in NI (P < 0.001) and −0.96 m/s per unit increase in IIR (P < 0.001). The magnitude of this change decreased with larger measurement area. Reproducibility of the association was observed with NI, but not with IIR. Conclusion: At clinically relevant spatial scales, comparable to area of a mapping catheter electrode, LGE-CMRI correlates with CV. Measurement scale is important in accurately quantifying the association of CV and LGE-CMRI intensity. Importantly, NI, but not IIR, accounts for changes in the dynamic range of CMRI and enables quantitative reproducibility of the association. [ABSTRACT FROM AUTHOR]

Aims: A prolonged PR interval may adversely affect ventricular filling and, therefore, cardiac function. AV delay can be corrected using right ventricular pacing (RVP), but this induces ventricular dyssynchrony, itself harmful. Therefore, in intermittent heart block, pacing avoidance algorithms are often implemented. We tested His‐bundle pacing (HBP) as an alternative. Methods: Outpatients with a long PR interval (>200 ms) and intermittent need for ventricular pacing were recruited. We measured within‐patient differences in high‐precision hemodynamics between AV‐optimized RVP and HBP, as well as a pacing avoidance algorithm (Managed Ventricular Pacing [MVP]). Results: We recruited 18 patients. Mean left ventricular ejection fraction was 44.3 ± 9%. Mean intrinsic PR interval was 266 ± 42 ms and QRS duration was 123 ± 29 ms. RVP lengthened QRS duration (+54 ms, 95% CI 42–67 ms, p <.0001) while HBP delivered a shorter QRS duration than RVP (−56 ms, 95% CI −67 to −46 ms, p <.0001). HBP did not increase QRS duration (−2 ms, 95% CI −8 to 13 ms, p =.6). HBP improved acute systolic blood pressure by mean of 5.0 mmHg (95% CI 2.8–7.1 mmHg, p <.0001) compared to RVP and by 3.5 mmHg (95% CI 1.9–5.0 mmHg, p =.0002) compared to the pacing avoidance algorithm. There was no significant difference in hemodynamics between RVP and ventricular pacing avoidance (p =.055). Conclusions: HBP provides better acute cardiac function than pacing avoidance algorithms and RVP, in patients with prolonged PR intervals. HBP allows normalization of prolonged AV delays (unlike pacing avoidance) and does not cause ventricular dyssynchrony (unlike RVP). Clinical trials may be justified to assess whether these acute improvements translate into longer term clinical benefits in patients with bradycardia indications for pacing. [ABSTRACT FROM AUTHOR]

Aims: Abnormal rate adaptation of the action potential is proarrhythmic but is difficult to measure with current electro-anatomical mapping techniques. We developed a method to rapidly quantify spatial discordance in whole heart activation in response to rate cycle length changes. We test the hypothesis that patients with underlying channelopathies or history of aborted sudden cardiac death (SCD) have a reduced capacity to maintain uniform activation following exercise.Methods and Results: Electrocardiographical imaging (ECGI) reconstructs >1200 electrograms (EGMs) over the ventricles from a single beat, providing epicardial whole heart activation maps. Thirty-one individuals [11 SCD survivors; 10 Brugada syndrome (BrS) without SCD; and 10 controls] with structurally normal hearts underwent ECGI vest recordings following exercise treadmill. For each patient, we calculated the relative change in EGM local activation times (LATs) between a baseline and post-exertion phase using custom written software. A ventricular conduction stability (V-CoS) score calculated to indicate the percentage of ventricle that showed no significant change in relative LAT (<10 ms). A lower score reflected greater conduction heterogeneity. Mean variability (standard deviation) of V-CoS score over 10 consecutive beats was small (0.9 ± 0.5%), with good inter-operator reproducibility of V-CoS scores. Sudden cardiac death survivors, compared to BrS and controls, had the lowest V-CoS scores post-exertion (P = 0.011) but were no different at baseline (P = 0.50).Conclusion: We present a method to rapidly quantify changes in global activation which provides a measure of conduction heterogeneity and proof of concept by demonstrating SCD survivors have a reduced capacity to maintain uniform activation following exercise. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: A spontaneous type I electrocardiogram (ECG) pattern and/or unheralded syncope are conventionally used as risk markers for primary prevention of sudden cardiac arrest/death (SCA/SCD) in Brugada syndrome (BrS). In this study, we determine the prevalence of conventional and newer markers of risk in those with and without previous aborted SCA events. Methods: All patients with BrS were identified at our institute. History of symptoms was obtained from medical tests or from interviews. Other markers of risk were also obtained, such as presence of (1) spontaneous type I pattern, (2) fractionated QRS (fQRS), (3) early repolarization (ER) pattern, (4) late potentials on signal‐averaged ECG (SAECG), and (5) response to programmed electrical stimulation. Results: In 133 patients with Bars, 10 (7%) patients (mean age = 39 ± 11 years; nine males) were identified with a previous ventricular fibrillation/ventricular tachycardia episode (n = 8) or requiring cardio‐pulmonary resuscitation (n = 2). None of these patients had a prior history of syncope before their SCA event. Only two (20%) patients reported a history of palpitations or dizziness. None had apneic breathing and three (30%) patients had a family history of SCA. From their ECGs, a spontaneous pattern was only found in one (10%) of these patients. Further, 10% of patients had fQRS, 17% had late potentials on SAECG, 20% had deep S waves in lead I, and 10% had an ER pattern in the peripheral leads. No significant differences were observed in the non‐SCA group. Conclusion: The majority of BrS patients with previous aborted SCA events did not have a spontaneous type I and/or prior history of syncope. Conventional and newer markers of risk appear to only have limited ability to predict SCA. [ABSTRACT FROM AUTHOR]

Aims Atrial fibrillation (AF) wavefront dynamics are complex and difficult to interpret, contributing to uncertainty about the mechanisms that maintain AF. We aimed to investigate the interplay between rotors, wavelets, and focal sources during fibrillation. Methods and results Arrhythmia wavefront dynamics were analysed for four optically mapped canine cholinergic AF preparations. A bilayer computer model was tuned to experimental preparations, and varied to have (i) fibrosis in both layers or the epicardium only, (ii) different spatial acetylcholine distributions, (iii) different intrinsic action potential duration between layers, and (iv) varied interlayer connectivity. Phase singularities (PSs) were identified and tracked over time to identify rotational drivers. New focal wavefronts were identified using phase contours. Phase singularity density and new wavefront locations were calculated during AF. There was a single dominant mechanism for sustaining AF in each of the preparations, either a rotational driver or repetitive new focal wavefronts. High-density PS sites existed preferentially around the pulmonary vein junctions. Three of the four preparations exhibited stable preferential sites of new wavefronts. Computational simulations predict that only a small number of connections are functionally important in sustaining AF, with new wavefront locations determined by the interplay between fibrosis distribution, acetylcholine concentration, and heterogeneity in repolarization within layers. Conclusion We were able to identify preferential sites of new wavefront initiation and rotational activity, in order to determine the mechanisms sustaining AF. Electrical measurements should be interpreted differently according to whether they are endocardial or epicardial recordings. [ABSTRACT FROM AUTHOR]

Aims: Atrial fibrillation (AF) wavefront dynamics are complex and difficult to interpret, contributing to uncertainty about the mechanisms that maintain AF. We aimed to investigate the interplay between rotors, wavelets, and focal sources during fibrillation.Methods and Results: Arrhythmia wavefront dynamics were analysed for four optically mapped canine cholinergic AF preparations. A bilayer computer model was tuned to experimental preparations, and varied to have (i) fibrosis in both layers or the epicardium only, (ii) different spatial acetylcholine distributions, (iii) different intrinsic action potential duration between layers, and (iv) varied interlayer connectivity. Phase singularities (PSs) were identified and tracked over time to identify rotational drivers. New focal wavefronts were identified using phase contours. Phase singularity density and new wavefront locations were calculated during AF. There was a single dominant mechanism for sustaining AF in each of the preparations, either a rotational driver or repetitive new focal wavefronts. High-density PS sites existed preferentially around the pulmonary vein junctions. Three of the four preparations exhibited stable preferential sites of new wavefronts. Computational simulations predict that only a small number of connections are functionally important in sustaining AF, with new wavefront locations determined by the interplay between fibrosis distribution, acetylcholine concentration, and heterogeneity in repolarization within layers.Conclusion: We were able to identify preferential sites of new wavefront initiation and rotational activity, in order to determine the mechanisms sustaining AF. Electrical measurements should be interpreted differently according to whether they are endocardial or epicardial recordings. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Introduction We hypothesized that very high-density mapping of typical atrial flutter (AFL) would facilitate a more complete understanding of its circuit. Such very high-density mapping was performed with the RhythmiaTM (Boston Scientific) mapping system using its 64 electrode basket catheter. Methods and results Data were acquired from 13 patients in AFL. Functional anatomy of the right atrium (RA) was readily identified during mapping including the Crista Terminalis and Eustachian ridge. The leading edge of the activation wavefront was identified without interruption and its conduction velocity (CV) was calculated. CV was not different at the cavotricuspid isthmus (CTI) compared to the remainder of the RA (1.02 vs. 1.03 m/s, P = 0.93). The sawtooth pattern of the surface electrocardiogram (EKG) flutter waves was compared to the position of the dominant wavefront. The downslope of the surface EKG flutter waves represented on average 73% ± 9% of the total flutter cycle length. During the downslope, the activation wavefront traveled significantly further than during the upslope (182 ± 21 milliseconds vs. 68 ± 29 milliseconds, P < 0.0001) with no change in CV between the two phases (0.88 vs. 0.91 m/s, P = 0.79). Conclusion CV at the CTI is not slower than other RA regions during typical AFL. The gradual downslope of the sawtooth EKG is not due to slow conduction at the CTI suggesting that success of ablation at this site relates to anatomical properties rather than the presence of a 'slow isthmus.' [ABSTRACT FROM AUTHOR]

Extracellular electrograms recorded during atrial fibrillation (AF) are challenging to interpret due to the inherent beat-to-beat variability in amplitude and duration. Phase mapping represents these voltage signals in terms of relative position within the cycle, and has been widely applied to action potential and unipolar electrogram data of myocardial fibrillation. To date, however, it has not been applied to bipolar recordings, which are commonly acquired clinically. The purpose of this study is to present a novel algorithm for calculating phase from both unipolar and bipolar electrograms recorded during AF. A sequence of signal filters and processing steps are used to calculate phase from simulated, experimental, and clinical, unipolar and bipolar electrograms. The algorithm is validated against action potential phase using simulated data (trajectory centre error <0.8 mm); between experimental multi-electrode array unipolar and bipolar phase; and for wavefront identification in clinical atrial tachycardia. For clinical AF, similar rotational content ( R = 0.79) and propagation maps (median correlation 0.73) were measured using either unipolar or bipolar recordings. The algorithm is robust, uses standard signal processing techniques, and accurately quantifies AF wavefronts and sources. Identifying critical sources, such as rotors, in AF, may allow for more accurate targeting of ablation therapy and improved patient outcomes. [ABSTRACT FROM AUTHOR]

Background: Adenosine is the first-line pharmacotherapy for termination of supraventricular tachycardia through its action on the atrioventricular node. However, pro-arrhythmic effects of adenosine are also recognised, most notably in the presence of pre-excited atrial fibrillation. In this case report, we describe the induction of ventricular fibrillation in a patient with no demonstrable accessory pathway, nor any other structural heart disease. This rare, idiosyncratic reaction has never previously been reported and is of relevance given the widespread and routine use of adenosine in clinical practice.Case Presentation: A 26-year-old woman of Cypriot origin presented to our emergency department with a sudden onset of palpitations and chest discomfort. She was healthy, with no previous medical history and no regular medications. An electrocardiogram demonstrated a narrow complex tachycardia with a rate of 194 beats per minute. Following failure of vagal maneuvers to terminate the tachycardia, the assessing physician administered a single intravenous dose of 6 mg adenosine. Our patient instantaneously developed coarse ventricular fibrillation and circulatory collapse. Cardiopulmonary resuscitation was initiated and our patient was rapidly defibrillated to sinus rhythm with a single 150 J direct current shock. A 900-mg loading dose of intravenous amiodarone was commenced and our patient was managed in the cardiac high dependency unit. No further arrhythmias were identified on continuous cardiac monitoring. On review, her presenting electrocardiogram had demonstrated rapidly conducted atrial fibrillation with no evidence of ventricular pre-excitation. Concordantly, her resting electrocardiogram was not suggestive of any accessory pathway. This was conclusively excluded on invasive electrophysiology study, with negative programmed ventricular stimulation up to three extrastimuli. Extensive laboratory investigations were unremarkable and failed to identify an underlying cause for her episode of atrial fibrillation. Furthermore, cardiac magnetic resonance imaging demonstrated a structurally normal heart, with no edema, fibrosis or infarction as well as normal coronary artery anatomy.Conclusions: Adenosine remains a safe and highly efficacious therapy for supraventricular tachycardia. However, this unusual case demonstrates the ability of adenosine to induce circulatory collapse and reminds the clinician that prompt access to resuscitation, defibrillation, and transcutaneous pacing equipment is mandatory with every administration of this drug. [ABSTRACT FROM AUTHOR]

Background Quadripolar left ventricular pacing leads permit a variety of pacing configurations from different sites within a coronary vein. There may be advantages to selecting a specific pacing vector. This study examines whether the range of cardiac outputs obtained at cardiac resynchronization therapy (CRT) implantation is greater between different poles within a vein, or greater between two different veins. Methods and Results The cardiac index (CI, L/min/m2) was measured during CRT implantation using a noninvasive cardiac output monitor (NICOM™, Cheetah Medical Inc., Newton Center, MA, USA) and a quadripolar left ventricle (LV) lead, in 22 patients with sinus rhythm. CI was recorded during right atrial-biventricular pacing at 70/min with fixed atrioventricular and ventriculo-ventricular delay, from each LV electrode in one vein, and then from an alternate vein. Phrenic nerve stimulation (PNS) occurred in nine of 15 posterior and three of 21 anterior veins (P = 0.005). At least one electrode in each vein had no PNS. The mean (standard deviation [SD]) difference between best and worst CI within any one vein was 13.1% (±9%). The mean (SD) difference between the best CI in one vein compared to the other was 9.8% (±8%; P = 0.043). In 16 of 22 patients, the range of CI was greater between poles within one vein, rather than between two veins (best of one vein compared to best from the other). In four of 22 patients, the range was greater between veins (P = 0.0003). Conclusion A greater range of CI is found within a single vein than between two different veins. This finding has implications both for the approach to implant technique and postimplant programming and optimization. [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]

Introduction: We sought to investigate the use of tissue contact monitoring by means of the electrical coupling index (ECI) in a prospective randomised control trial of patients undergoing cavotricuspid isthmus (CTI) ablation for atrial flutter. Methods: Patients with ECG-documented typical flutter undergoing their first CTI ablation were randomised to ECI™-guided or non-ECI™-guided ablation. An irrigated-tip ablation catheter was used in all cases. Consecutive 50-W, 60-s radiofrequency lesions were applied to the CTI, from the tricuspid valve to inferior vena cava, with no catheter movement permitted during radiofrequency (RF) delivery. The ablation endpoint was durable CTI block at 20 min post-ablation. Patients underwent routine clinic follow-up post-operatively. Results: A total of 101 patients (79 male), mean age 66 (+/−11), 50 ECI-guided and 51 control cases were enrolled in the study. CTI block was achieved in all. There were no acute complications. All patients were alive at follow-up. CTI block was achieved in a single pass in 36 ECI-guided and 30 control cases ( p = 0.16), and at 20 min post-ablation, re-conduction was seen in 5 and 12 cases, respectively ( p = 0.07). There was no significant difference in total procedure time (62.7 ± 33 vs. 62.3 ± 33 min, p = 0.92), RF requirement (580 ± 312 vs. 574 ± 287 s, p = 0.11) or fluoroscopy time (718 ± 577 vs. 721 ± 583 s, p = 0.78). After 6 ± 4 months, recurrence of flutter had occurred in 1 (2 %) ECI vs. 8 (16 %) control cases (OR 0.13, 95 % CI 0.01-1.08, p = 0.06). Conclusions: ECI-guided CTI ablation demonstrated a non-statistically significant reduction in late recurrence of atrial flutter, at no cost to procedural time, radiation exposure or RF requirement. [ABSTRACT FROM AUTHOR]

Introduction: We sought to investigate the use of tissue contact monitoring by means of the electrical coupling index (ECI) in a prospective randomised control trial of patients undergoing cavotricuspid isthmus (CTI) ablation for atrial flutter.Methods: Patients with ECG-documented typical flutter undergoing their first CTI ablation were randomised to ECI™-guided or non-ECI™-guided ablation. An irrigated-tip ablation catheter was used in all cases. Consecutive 50-W, 60-s radiofrequency lesions were applied to the CTI, from the tricuspid valve to inferior vena cava, with no catheter movement permitted during radiofrequency (RF) delivery. The ablation endpoint was durable CTI block at 20 min post-ablation. Patients underwent routine clinic follow-up post-operatively.Results: A total of 101 patients (79 male), mean age 66 (+/-11), 50 ECI-guided and 51 control cases were enrolled in the study. CTI block was achieved in all. There were no acute complications. All patients were alive at follow-up. CTI block was achieved in a single pass in 36 ECI-guided and 30 control cases (p = 0.16), and at 20 min post-ablation, re-conduction was seen in 5 and 12 cases, respectively (p = 0.07). There was no significant difference in total procedure time (62.7 ± 33 vs. 62.3 ± 33 min, p = 0.92), RF requirement (580 ± 312 vs. 574 ± 287 s, p = 0.11) or fluoroscopy time (718 ± 577 vs. 721 ± 583 s, p = 0.78). After 6 ± 4 months, recurrence of flutter had occurred in 1 (2 %) ECI vs. 8 (16 %) control cases (OR 0.13, 95 % CI 0.01-1.08, p = 0.06).Conclusions: ECI-guided CTI ablation demonstrated a non-statistically significant reduction in late recurrence of atrial flutter, at no cost to procedural time, radiation exposure or RF requirement. [ABSTRACT FROM AUTHOR]

Background: Radiation exposure is a major concern in cardiac device implantation, especially cardiac resynchronization therapy (CRT) procedures. The RadPad™ (Worldwide Innovations & Technologies, Inc., Kansas City, MO, USA), a radiation-attenuating adhesive drape, has been shown to be beneficial in several clinical settings involving fluoroscopy, but less is known about the actual benefits in CRT procedures. Methods: Consecutive CRT implants performed with and without a RadPad™ drape over a 10-month period were analyzed. Two thermoluminescent dosimeters (TLDs) were attached to each implanting physician at several locations (adjacent to eyes, center abdomen [outside lead apron], left and right index fingers, and dorsum of the right foot). Results were corrected for background using control TLDs, and normalized to dose-area product (DAP). Results: Thirty-six patients (31 male), 16 with and 20 without the RadPad™, were included in the study. No technical problems were caused by the presence of the radiation-absorbing drape. Time required to position the drape never exceeded 30 seconds, no acute skin reactions were noted, and no radiationabsorbing drape became displaced. Despite a trend toward longer fluoroscopy times and higher DAPs in the radiation-absorbing drape group, radiation exposure was significantly reduced: 65% in the case of the hands and body (P < 0.001), and 40% the eyes (P < 0.01). Conclusion: The use of a radiation-absorbing drape results in a significant reduction in radiation dose to the implanting physician during CRT procedures. Not only is the dose to the hands reduced, but also the eye and body doses are significantly reduced. The routine use of radiation-absorbing drapes should be considered for all CRT implant procedures in the light of these findings. [ABSTRACT FROM AUTHOR]

Background There are limited data on the use of a remote robotic catheter system (RCS) for mitral isthmus (MI) ablation. Methods This single-center, prospective, matched control study included 45 patients who underwent atrial fibrillation ablation using a remote RCS compared to 45 patients who underwent conventional ablation. All patients had circumferential pulmonary vein isolation (PVI), roof, and MI ablation. Results There were no significant differences in baseline clinical characteristics. There were no significant differences in MI block (RCS: 44/45 [98%] vs Control: 43/45 [96%], P = 1.0), roof block (RCS: 45/45 [100%] vs Control: 44/45 [98%], P = 1.0), and PVI (RCS: 45/45 [100%] vs Control: 45/45 [100%], P = 1.0). Ablation and procedural times were similar in both arms. Using RCS, mean total MI ablation and procedure times were 13 ± 6 minutes and 23 ± 15 minutes, respectively. Coronary sinus (CS) ablation was significantly less in the RCS arm (48% vs 72%, P = 0.03). It was possible to 'drive' the ablation catheter into the distal CS using the RCS in 19/22 (86%) patients. There was a significant trend of reduction in mean MI ablation (P = 0.008) and procedural times (P = 0.004) over the course of the study period. There was a significant reduction in fluoroscopy time in the RNS arm (33 ± 17 minutes vs 49 ± 20 minutes, P = 0.0004). Conclusion It is feasible and safe to use a remote RCS for MI ablation, including 'driving into the CS.' MI block was achieved in 98% with a significant reduction in the need for CS ablation (48%). There is a short learning curve. [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]

Case Series of Mitral Isthmus Ablation. Background: Mitral isthmus ablation is challenging. The use of steerable sheath and high ablation power may improve success rate. Methods: This single-center, prospective study enrolled 200 patients who underwent ablation for atrial fibrillation (AF), including mitral isthmus ablation. Mitral isthmus ablation was performed using an irrigated ablation catheter via a steerable sheath (endocardium: maximum power: 40/50 W limited to annular end, maximum temperature: 48 °C; coronary sinus [CS]: maximum power: 25/30 W, maximum temperature: 48 °C). Endpoint was bidirectional mitral isthmus block. Results: Mitral isthmus block was acutely achieved in 182/200 patients (91%). Sixty-nine percent of patients required CS ablation. Mean total ablation time was 13 ± 6 minutes. There was 1 case of acute circumflex artery occlusion. Mean left atrium (LA) diameter was significantly bigger in patients with unsuccessful mitral isthmus ablation (49 ± 4 mm vs. 43 ± 6 mm; P = 0.0007). In redo procedures, the incidence of reconduction at the mitral isthmus, roof and cavotricuspid isthmus was 44%, 37%, and 29%, respectively. Overall incidence of perimitral flutter was 9%. Prior complex fractionated atrial electrogram ablation was a predictor for microreentrant atrial tachycardia (AT) whereas gaps in linear lesions predicted macroreentrant flutters. After a mean follow-up of 20 ± 9 months, 73% of patients remained free from AF or AT. Conclusion: We reported on a series of mitral isthmus ablation using steerable sheath and high ablation power (50 W). Larger LA diameter was a predictor of failure to achieve mitral isthmus block. The mitral isthmus had a moderately high incidence of re-conduction but was only associated with a relatively low incidence of perimitral flutter. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1193-1200, November 2012) [ABSTRACT FROM AUTHOR]

Aims Ensuring complete block after left atrial (LA) linear lesions is important as partial block may be pro-arrhythmic. Techniques to confirm roof line block may be time consuming and challenging and have not been well described. This study investigates whether local activation times (LAT) during left atrial appendage (LAA) pacing help in the assessment of roof line block. Methods and results Forty-five patients underwent ablation for atrial fibrillation (AF) including circumferential pulmonary vein isolation, roof, and mitral isthmus lines. Local activation times were measured at pre-defined points on the posterior wall and high anterior wall during LAA pacing at the following stages: (i) baseline; (ii) incomplete roof line; (iii) roof block; and (iv) roof and mitral isthmus block. Time from pacing at high posterior wall to LAA was also recorded at each stage. Receiver operator curve analyses were performed on different parameters to assess if they could confirm roof line block. There was a stepwise increase in mean high posterior wall LAT: 83 ± 16 ms (baseline); 105 ± 20 ms (incomplete roof block); 133 ± 26 ms (roof block), and 152 ± 35 ms (roof and MI block; one way analysis of variance, P< 0.0001). Increased LA diameter, amiodarone use, and adjunctive complex fractionated atrial electrogram ablation were associated with longer LATs. For patients with persistent AF, LAA to high posterior wall times of >133 ms, high posterior wall to LAA times of >125 ms and double potential >77 ms predict roof line block with high specificity and sensitivity especially if there was also mitral isthmus block. Conclusion Parameters derived from the measurement of LAT of the high posterior and anterior LA wall help guide the assessment of roof line block. [ABSTRACT FROM PUBLISHER]

Aims Mitral isthmus (MI) ablation is technically challenging, requiring long endocardial ablation times and frequently coronary sinus (CS) ablation. The circumflex artery lies in the epicardium in close proximity to the CS and the mitral annulus and may potentially be injured during radiofrequency ablation. Methods and results Fifty-four patients underwent catheter ablation procedures that included MI ablation for treatment of atrial fibrillation. Irrigated ablation catheters were used with the following settings: endocardial surface (max power: 40/50 W at the annular end; max temperature: 48°C); CS (max power: 25/30 W; max temperature: 48°C). Coronary angiography was performed pre- and post-ablation and analysed by two cardiologists with quantitative coronary angiography. Mitral isthmus block was achieved in 89% of patients (60% required CS ablation). Fifteen patients (28%) had angiographic changes following ablation: eight had mid-circumflex narrowing only, one had circumflex and obtuse marginal (OM) artery narrowing, one had OM narrowing only, and five had distal circumflex occlusion/narrowing. Five patients had significant narrowing (50–84%), which resolved with intracoronary glycerine trinitrate. Fourteen (93%) of the patients with circumflex ‘injury’ had CS ablation and a longer mean CS ablation time (5.0 ± 3.0 vs. 2.6 ± 3.3 min, P = 0.03). Patients with distal circumflex occlusion had significantly smaller vessel diameter (1.0 ± 0.1 vs. 2.1 ± 0.2 mm, P = 0.03). A shorter distance between the circumflex and the CS was also associated with circumflex ‘injury’ (3.2 ± 1.9 vs. 5.6 ± 3.2 mm, P = 0.04). There were no electrocardiographic or echocardiographic abnormalities and no angina symptoms during follow-up. Conclusion Acute sub-clinical circumflex ‘injury’ following MI ablation is not uncommon. Ablation within the CS, proximity of the circumflex and the CS, and a small distal circumflex were risk factors for ‘injury’. [ABSTRACT FROM PUBLISHER]

Aims Mitral isthmus ablation is technically challenging, often requiring both endocardial and epicardial coronary sinus (CS) ablation. Blood flow in the CS and circumflex artery may act as a ‘heat sink’ and reduce the efficacy of radiofrequency ablation. This study investigates how the CS and circumflex artery diameters affect mitral isthmus ablation. Methods and results Thirty-five patients underwent ablation for atrial fibrillation. Irrigated-tip catheters were used during mitral isthmus ablation with the following settings: endocardial surface (maximum power: 40–50 W at the annular end of line; maximum temperature: 48°C); CS (maximum power: 25–30 W; maximum temperature: 48°C). The absence of block after 10 min of endocardial ablation led to CS ablation for up to 5 min. If there was still no block, further ablation was at the discretion of the physician. Coronary angiography and CS venography were performed and analysed with quantitative coronary angiography. Mitral isthmus block was achieved in 31 patients (89%). Twenty-three patients (74%) required CS ablation to achieve block. These patients were found to have significantly larger CS diameters (6.5 ± 1.2 vs. 5.4 ± 0.5 mm, P< 0.02). Coronary sinus diameter >59 mm predicted the need for CS ablation (specificity: 100%; sensitivity: 78%). Coronary sinus diameter correlated significantly with total mitral isthmus ablation time (r= 0.52, P< 0.003) and CS ablation time (r= 0.59, P< 0.0005), whereas circumflex diameter did not. Conclusion Larger-diameter CS is associated with a need for CS ablation during mitral isthmus ablation. Coronary sinus but not circumflex diameter was significantly correlated with total and CS ablation time, supporting the hypothesis that the CS but not the circumflex artery acts as a heat sink. [ABSTRACT FROM PUBLISHER]