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Aims Cardiac resynchronization therapy programmed to dynamically fuse pacing with intrinsic conduction using atrioventricular (AV) timing algorithms (e.g. SyncAV) has shown promise; however, mechanistic data are lacking. This study assessed the impact of SyncAV on electrical dyssynchrony across various pacing modalities using non-invasive epicardial electrocardiographic imaging (ECGi). Methods and results Twenty-five patients with left bundle-branch block (median QRS duration (QRSd) 162.7 ms) and intact AV conduction (PR interval 174.0 ms) were prospectively enrolled. ECGi was performed acutely during biventricular pacing with fixed nominal AV delays (BiV) and using SyncAV (optimized for the narrowest QRSd) during: BiV + SyncAV, LV-only single-site (LVSS + SyncAV), MultiPoint pacing (MPP + SyncAV), and LV-only MPP (LVMPP + SyncAV). Dyssynchrony was quantified via ECGi (LV activation time, LVAT; RV activation time, RVAT; LV electrical dispersion index, LVEDi; ventricular electrical uncoupling index, VEU; and biventricular total activation time, VVtat). Intrinsic conduction LVAT (124 ms) was significantly reduced by BiV pacing (109 ms) (P = 0.001) and further reduced by LVSS + SyncAV (103 ms), BiV + SyncAV (103 ms), LVMPP + SyncAV (95 ms), and MPP + SyncAV (90 ms). Intrinsic RVAT (93 ms), VVtat (130 ms), LVEDi (36 ms), VEU (50 ms), and QRSd (163 ms) were reduced by SyncAV across all pacing modes. More patients exhibited minimal LVAT, VVtat, LVEDi, and QRSd with MPP + SyncAV than any other modality. Conclusion Dynamic AV delay programming targeting fusion with intrinsic conduction significantly reduced dyssynchrony, as quantified by ECGi and QRSd for all evaluated pacing modes. MPP + SyncAV achieved the greatest synchrony overall but not for all patients, highlighting the value of pacing mode individualization during fusion optimization. [ABSTRACT FROM AUTHOR]

Aims: Optimum timing of pacemaker implantation following cardiac surgery is a clinical challenge. European and American guidelines recommend observation, to assess recovery of atrioventricular block (AVB) (up to 7 days) and sinus node (5 days to weeks) after cardiac surgery. This study aims to determine rates of cardiac implantable electronic devices (CIEDs) implants post-surgery at a high-volume tertiary centre over 3 years. Implant timing, patient characteristics and outcomes at 6 months including pacemaker utilization were assessed.Methods and Results: All cardiac operations (n = 5950) were screened for CIED implantation following surgery, during the same admission, from 2015 to 2018. Data collection included patient, operative, and device characteristics; pacing utilization and complications at 6 months. A total of 250 (4.2%) implants occurred; 232 (3.9%) for bradycardia. Advanced age, infective endocarditis, left ventricle systolic impairment, and valve surgery were independent predictors for CIED implants (P < 0.0001). Relative risk (RR) of CIED implants and proportion of AVB increased with valve numbers operated (single-triple) vs. non-valve surgery: RR 5.4 (95% CI 3.9-7.6)-21.0 (11.4-38.9) CIEDs. Follow-up pacing utilization data were available in 91%. Significant utilization occurred in 82% and underutilization (<1% A and V paced) in 18%. There were no significant differences comparing utilization rates in early (≤day 5 post-operatively) vs. late implants (P = 0.55).Conclusion: Multi-valve surgery has a particularly high incidence of CIED implants (14.9% double, 25.6% triple valve). Age, left ventricle systolic impairment, endocarditis, and valve surgery were independent predictors of CIED implants. Device underutilization was infrequent and uninfluenced by implant timing. Early implantation (≤5 days) should be considered in AVB post-multi-valve surgery. [ABSTRACT FROM AUTHOR]

Background: A novel active fixation coronary sinus (CS) lead, Attain Stability (AS), has been released aiming to improve targeted lead positioning. Rather than being wedged into the distal vessel, it relies on a side helix for fixation. We aimed to compare implant procedure parameters and electromechanical stability of the AS lead with passive CS leads. Methods: A retrospective study involving six major UK cardiac centers. Patients who received active fixation leads were compared with passive fixation lead recipients in a 1:2 ratio. The primary outcome was total lead displacements (combined macrodisplacement/microdisplacement, defined as displacements requiring repositioning procedures, an increase in threshold ≥0.5 V or pulse width ≥0.5 ms, or a change in pacing polarity). Results: A total of 761 patients were included (253 AS leads and 508 passive fixation leads), of which 736 had follow‐up data. The primary endpoint rate was 31% (75/241) in the active and 43% (214/495) in the passive group (p =.002). Six patients (2.5%) in the active group and 14 patients (2.8%) in the passive group required CS lead repositioning procedures (p = 0.981). On multivariable analysis, active leads were associated with a reduction in lead displacements, odds ratio 0.66 (95% confidence interval: 0.46–0.95), p =.024. There were differences in favor of passive leads in procedure duration, 120 (96–149) versus 127 (105–155) min (p =.008), and fluoroscopy time, 17 (11–26) versus 18.5 (13–27) min (p =.0022). The median follow‐up duration was similar (active vs. passive): 31 (17–47) versus 34 (16–71) weeks, (p =.052). Conclusion: AS CS leads had improved electromechanical stability compared with passive fixation leads, with only minimal increases in implant procedure and fluoroscopy times. [ABSTRACT FROM AUTHOR]

Introduction: Atrial fibrillation (AF)-induced cardiomyopathy (AIC) is retrospectively defined after normalisation of left ventricular ejection fraction (LVEF) in sinus rhythm. It is unclear why some patients develop AIC., Hypothesis: Patients with AIC have a subtle cardiomyopathic process that precedes their AF-mediated LVEF reduction. Detailed assessment of cardiac function after successful catheter ablation will reveal this., Objective: To evaluate the utility of measures to identify cardiomyopathic features that persist after LVEF normalisation in AIC., Methods: Patients with rate-controlled persistent AF and LVEF<50% undergoing catheter ablation (CA) were prospectively evaluated using echocardiography, cardio-pulmonary exercise testing and serum N-terminal pro b-type natriuretic peptide (NT-proBNP) at baseline and 6 months after CA. Participants with AIC, (LVEF recovery (≥50%) and no other cause for cardiac dysfunction) were evaluated using left ventricular (LV) longitudinal strain and left atrial (LA) reservoir strain (LARS). Changes in peak oxygen consumption and the minute ventilation/carbon dioxide production slope were measured as markers of functional capacity and ventilatory inefficiency. A control group of patients with persistent AF with preserved LVEF were also enrolled., Results: 34/41 (82.9%) participants recovered LVEF in sinus rhythm; defined as AIC. NT-proBNP levels were elevated in 18 (52.9%), and 16 reported ongoing heart failure (HF) symptoms. 10 (29.4%) had no improvement in functional capacity, and seven (20.6%) showed persistent ventilatory inefficiency. 20 (58.8%) had impaired global LV longitudinal strain with a relative apical sparing pattern. Nine (26.5%) had impaired LARS. There was an overlap of these abnormalities. 32 (94.1%) demonstrated at least one, 17 (50.0%) having no cardiovascular risk factors. Patients with preserved LVEF during persistent AF had similar demographics but a lower burden of short R-R intervals (<660 ms) on Holter monitoring., Discussion: Abnormal structural, metabolic and HF biomarkers are seen in patients with AIC in sinus rhythm. These features may represent a precedent subtle cardiomyopathic process predisposing them to left ventricular systolic dysfunction in AF., Trial Registration Number: NCT04987723., Competing Interests: Competing interests: RJH has received research grants and educational grants from Medtronic and Biosense Webster, and speaker fees and travel grants from Abbott and Biosense Webster and Medtronic. RS has received research grants and educational grants from Abbott and Biosense Webster and Medtronic, and speaker fees and travel grants from Abbott and Biosense Webster and Medtronic. RJH, SH and RS were inventors of the STAR mapping system and are shareholders in Rhythm AI. The remaining authors have nothing to disclose., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: In ventricular tachycardia (VT), optimal substrate mapping strategies identifying arrhythmogenic sites are not established., Objectives: This study sought to evaluate multidirectional pacing on the distribution of specific conduction and repolarization metrics to localize re-entrant VT sites in a porcine infarct model., Methods: Substrate maps were created in 13 pigs with chronic myocardial infarction using the Advisor HD Grid (Abbott) during right ventricular (RV), left ventricular, biventricular pacing (BIV), and sinus rhythm (SR). Critical VT sites of early-, mid-, and late-diastolic signals were delineated. Vulnerable sites to re-entry were defined as sites of latest activation timing within and post-QRS complex, largest activation and activation-recovery interval gradients. Distances between the 20 most vulnerable sites and diastolic VT points were measured, and identification of VT points was assessed using the area under the receiver-operating characteristic curve., Results: A total of 34 VTs were mapped, and 48 sinus and pacing maps were obtained (10 BIV, 13 left ventricular, 13 RV, 12 SR). Late potential mapping in SR was taken as the established clinical standard for comparison. Latest activation time with BIV pacing provided the closest localization for VT isthmus (median 5.5 mm; IQR: 7.15 mm; P < 0.005). The gradient of activation-recovery interval using RV pacing had closest localization for VT exit and entrance (median 10.6 mm; IQR: 5.0 mm; P < 0.005 and 9.4 mm; IQR: 8.0 mm; P < 0.05). Global sensitivity and specificity analysis showed that gradient of activation-recovery interval in SR achieved the highest area under the receiver-operating characteristic curve, with similar results from the gradient of activation timing., Conclusions: Multidirectional pacing in combination with conduction and repolarization parameters enables better localization of VT diastolic critical sites vs SR late potentials., Competing Interests: Funding Support and Author Disclosures This study was supported with research funding from Abbott UK. Dr Lambiase is supported by UCL/UCLH Biomedicine National Institute for Health and Care Research, Barts BRC, and the Stephen Lyness Memorial Fund. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Aims: Cardiac resynchronization therapy programmed to dynamically fuse pacing with intrinsic conduction using atrioventricular (AV) timing algorithms (e.g. SyncAV) has shown promise; however, mechanistic data are lacking. This study assessed the impact of SyncAV on electrical dyssynchrony across various pacing modalities using non-invasive epicardial electrocardiographic imaging (ECGi)., Methods and Results: Twenty-five patients with left bundle-branch block (median QRS duration (QRSd) 162.7 ms) and intact AV conduction (PR interval 174.0 ms) were prospectively enrolled. ECGi was performed acutely during biventricular pacing with fixed nominal AV delays (BiV) and using SyncAV (optimized for the narrowest QRSd) during: BiV + SyncAV, LV-only single-site (LVSS + SyncAV), MultiPoint pacing (MPP + SyncAV), and LV-only MPP (LVMPP + SyncAV). Dyssynchrony was quantified via ECGi (LV activation time, LVAT; RV activation time, RVAT; LV electrical dispersion index, LVEDi; ventricular electrical uncoupling index, VEU; and biventricular total activation time, VVtat). Intrinsic conduction LVAT (124 ms) was significantly reduced by BiV pacing (109 ms) (P = 0.001) and further reduced by LVSS + SyncAV (103 ms), BiV + SyncAV (103 ms), LVMPP + SyncAV (95 ms), and MPP + SyncAV (90 ms). Intrinsic RVAT (93 ms), VVtat (130 ms), LVEDi (36 ms), VEU (50 ms), and QRSd (163 ms) were reduced by SyncAV across all pacing modes. More patients exhibited minimal LVAT, VVtat, LVEDi, and QRSd with MPP + SyncAV than any other modality., Conclusion: Dynamic AV delay programming targeting fusion with intrinsic conduction significantly reduced dyssynchrony, as quantified by ECGi and QRSd for all evaluated pacing modes. MPP + SyncAV achieved the greatest synchrony overall but not for all patients, highlighting the value of pacing mode individualization during fusion optimization., Competing Interests: Conflict of interest: N.B., L.C.M., and J.O.M. are employees of Abbott., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Aims: To determine the incidence, clinical features, management, and outcomes of pacemaker (PM) and implantable cardioverter-defibrillator (ICD) lead cardiac perforation. Cardiac perforations due to PM and ICD leads are rare but serious complications. Clinical features vary widely and may cause diagnostic delay. Management strategies are non-guideline based due to paucity of data., Methods and Results: A multicentre retrospective series including 3 UK cardiac tertiary centres from 2016 to 2020. Patient, device, and lead characteristics were obtained including 6-month outcomes. Seventy cases of perforation were identified from 10 631 procedures; perforation rate was 0.50% for local implants. Thirty-nine (56%) patients were female, mean ( ± standard deviation) age 74 ( ± 13.8) years. Left ventricular ejection fraction 51 ( ± 13.2) %. Median time to diagnosis was 9 (range: 0-989) days. Computed tomography (CT) diagnosed perforation with 97% sensitivity. Lead parameter abnormalities were present in 86% (whole cohort) and 98.6% for perforations diagnosed >24 h. Chest pain was the commonest symptom, present in 46%. The management strategy was percutaneous in 98.6% with complete procedural success in 98.6%. Pericardial effusion with tamponade was present in 17% and was associated with significantly increased mortality and major complications. Anticoagulation status was associated with tamponade by multivariate analysis (odds ratio 21.7, 95% confidence interval: 1.7-275.5, P = 0.018)., Conclusions: Perforation was rare (0.50%) and managed successfully by a percutaneous strategy with good outcomes. Tamponade was associated with increased mortality and major complications. Anticoagulation status was an independent predictor of tamponade. Case complexity is highly variable and requires skilled operators with a multi-disciplinary approach to achieve good outcomes., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Aims: Optimum timing of pacemaker implantation following cardiac surgery is a clinical challenge. European and American guidelines recommend observation, to assess recovery of atrioventricular block (AVB) (up to 7 days) and sinus node (5 days to weeks) after cardiac surgery. This study aims to determine rates of cardiac implantable electronic devices (CIEDs) implants post-surgery at a high-volume tertiary centre over 3 years. Implant timing, patient characteristics and outcomes at 6 months including pacemaker utilization were assessed., Methods and Results: All cardiac operations (n = 5950) were screened for CIED implantation following surgery, during the same admission, from 2015 to 2018. Data collection included patient, operative, and device characteristics; pacing utilization and complications at 6 months. A total of 250 (4.2%) implants occurred; 232 (3.9%) for bradycardia. Advanced age, infective endocarditis, left ventricle systolic impairment, and valve surgery were independent predictors for CIED implants (P < 0.0001). Relative risk (RR) of CIED implants and proportion of AVB increased with valve numbers operated (single-triple) vs. non-valve surgery: RR 5.4 (95% CI 3.9-7.6)-21.0 (11.4-38.9) CIEDs. Follow-up pacing utilization data were available in 91%. Significant utilization occurred in 82% and underutilization (<1% A and V paced) in 18%. There were no significant differences comparing utilization rates in early (≤day 5 post-operatively) vs. late implants (P = 0.55)., Conclusion: Multi-valve surgery has a particularly high incidence of CIED implants (14.9% double, 25.6% triple valve). Age, left ventricle systolic impairment, endocarditis, and valve surgery were independent predictors of CIED implants. Device underutilization was infrequent and uninfluenced by implant timing. Early implantation (≤5 days) should be considered in AVB post-multi-valve surgery., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

A 73-year-old gentleman with dilated cardiomyopathy, left bundle branch block and a left ventricular (LV) ejection fraction of 20% was implanted with two LV leads in a tri-ventricular cardiac resynchronisation therapy defibrillator (CRT-D) trial. As a part of the trial he was programmed with fusion-based CRT therapy with dual LV lead only pacing. The patient presented to local heart failure service 12 years after implant, after a positive response to CRT therapy, with increase in fatigue, shortness of breath and bilateral pitting oedema. The patient sent a remote monitoring transmission that suggested loss of capture on one of the LV leads. This coupled with atrial ectopics was producing a high burden of pacemaker-mediated tachycardia (PMT) that was not seen when both LV leads had been capturing. What is the mechanism for this? Dual LV-lead tri-ventricular leads have been shown to have variable improvements in CRT response but with an increased complexity of implant procedure. This is the first case report of PMT-induced heart failure exacerbation in a tri-ventricular device following loss of LV capture of one lead., (© 2020 Wiley Periodicals LLC.)

Background: We describe a case series of patients for a gradual rise in daily, low-voltage sub-threshold measurement (LVSM) of shock (high-voltage, HV) impedance in a group of patients with Boston Scientific implantable cardioverter-defibrillators (ICDs) and investigate the cause of the abnormality., Case Summary: Six patients presented with a gradual rise in HV impedance above normal range (132.5 ± 20.8 Ω). Patients were young with a mean age of 29 ± 11 years, four patients had hypertrophic cardiomyopathy, one left ventricular non-compaction, and one long QT. All lead designs were silicon body with GORE polytetrafluoroethylene (ePTFE) coated coils, and a lower true shock impedance (TSI) was seen in all cases with full output synchronized shock. We compared the rate of HV impedance rise with our historical cohort of Boston ICDs using an unpaired t -test. The change in impedance per month was significantly higher amongst our six patients when compared with our cohort of Boston Scientific ICDs (3.2 ± 1.9 Ω/month vs. 0.0008 ± 0.005 Ω/month, P  < 0.001). Patients were individually investigated and management discussed in a dedicated device multi-disciplinary team meeting (MDT)., Discussion: There are distinct differences between TSI and LVSM. The TSI is derived from a full output shock, whilst LVSM is calculated from a small current output. These cases highlight the inaccuracies of the LVSM measurement. The gradual rise in LVSM is significantly higher than the value for TSI in these patients we propose the most likely mechanism is encapsulation fibrosis surrounding the right ventricular shock coil. Management for these patients requires vigorous testing to rule out electrical failure, and replacement maybe necessary., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Cardiology.)

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., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions please email: journals.permissions@oup.com.)

Objectives: The goal of this study was to assess the impact of triventricular pacing (Tri-V) on long-term survival., Background: Biventricular pacing (Bi-V) is an important adjunctive treatment in advanced heart failure, but almost one-third of patients experience no improvement with this therapy and are labeled as nonresponders. Adding a third ventricular lead (Tri-V) has been shown to be feasible and provides favorable acute results when assessed by using echocardiographic, hemodynamic, and clinical endpoints. However, the long-term effects of Tri-V pacing and how it affects long-term survival remains unknown., Methods: This single-center, propensity score-matched cohort study compared 34 patients with advanced heart failure who underwent implantation with Tri-V devices versus 34 control subjects treated with Bi-V pacing. Clinical outcomes during a median of 2,478 days (IQR: 1,183 to 3,214 days) were compared., Results: Tri-V-treated patients compared with Bi-V-treated patients presented with a trend for shorter battery longevity (time to box change, 1,758 ± 360 days vs. 1,993 ± 408 days; p = 0.072). Incidence of lead dislodgement (Tri-V vs. Bi-V, 0.86 vs. 1.10 per 100 patient-years; p = 0.742), device-related infection (Tri-V vs. Bi-V, 1.83 vs. 1.76 per 100 patient-years; p = 0.996), and refractory phrenic nerve capture (Tri-V vs. Bi-V, 0.48 vs. 1.84 per 100 patient-years; p = 0.341) was comparable in the 2 groups. Episodes of ventricular arrhythmia requiring implantable cardioverter-defibrillator intervention occurred more frequently in the Bi-V group versus the Tri-V group (6.55 vs. 16.88 per 100 patient-years; adjusted hazard ratio: 0.31; 95% confidence interval: 0.14 to 0.66; p = 0.002). Lower all-cause mortality and heart transplant was observed in the Tri-V group compared with the Bi-V group (6.99 vs. 11.92 per 100 patient-years; adjusted hazard ratio: 0.44; 95% confidence interval: 0.23 to 0.85; p = 0.015)., Conclusions: Tri-V displayed a similar safety profile compared with Bi-V and was associated with potential benefits regarding long-term survival and ventricular arrhythmia burden., (Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Aims: Despite the increasing number of device implants worldwide, little is known about the early and late complications of cardiac resynchronisation therapy (CRT) or the incidence of these complications in patients with different heart failure aetiologies. We aim to determine procedural success and early and late complications in CRT patients., Methods and Results: All early (<90 days) and late (>90 days) complications occurring over 490 consecutive CRT procedures in 402 patients, from a large single-centre registry between 2000 and 2009 were analysed. Mean follow-up duration was 1012 ± 610 days. In addition, procedural data and long-term left ventricular (LV) lead performance were examined. The mean age of patients was 65 ± 15 years, 31% were female. The majority of devices (70%) were CRT-defibrillators. Left ventricular lead implantation was achieved after one or more than one attempt in 96.7% of patients (first procedure was successful in 95.1%). The incidence of early and late complications was 9.4% and 6.1% respectively. Infection and lead displacement were the most common complications. Dilated cardiomyopathy (DCM) was associated with significantly more complications than ischaemic cardiomyopathy (P = 0.01) and these occurred later in the DCM population. Long-term LV lead performance was comparable with that of right atrial and ventricular leads., Conclusion: Transvenous implantation of the LV lead is safe and achievable for CRT with high procedural success rates. For the first time we describe the late complications from CRT in different heart failure populations. This group of patients must be kept under surveillance, not only for heart failure events but also for device-related issues. The reasons for higher complication rates in DCM patients require further evaluation.

Aims: A significant proportion of patients implanted with biventricular (BiV) devices fail to respond. Clinical response may be improved by additional ventricular stimulation sites. This single-centre, double-blinded randomized crossover trial aimed to determine whether long-term multisite ventricular pacing is superior to conventional BiV pacing in heart failure patients., Methods and Results: A total of 43 patients referred for cardiac resynchronization therapy (CRT) underwent transvenous implantation of a triventricular (TriV) device. Pacing leads were positioned in the right ventricular (RV) apex and a lateral coronary sinus (CS) branch, with a third ventricular lead implanted in a further lateral CS branch in 23 patients (group A) and on the high RV septum in 20 patients (group B). Devices were programmed in a randomized order to four pre-determined pacing configurations: conventional BiV, TriV, and dual-site and single-site left bentricular (LV) or RV pacing for 3-month periods with clinical and echo assessment at the end of each period. The primary endpoint was the comparison of 6 min walk distance (6MW) after 3 months of BiV vs. TriV pacing; secondary endpoints were Minnesota Living With Heart Failure (MLWHF) scores, and LV dimensions and function. The 12-month follow-up period was completed by 37 patients. Compared with BiV pacing, TriV pacing resulted in significant improvements in 6MW (451 ± 112 m vs. 425 ± 119 m, P = 0.008), MLWHF (32 ± 19 vs. 38 ± 24, P = 0.036), LV end-systolic volume (158 ± 79mL vs. 168 ± 76 mL, P < 0.05), and ejection fraction (30 ± 8% vs. 27 ± 8%, P < 0.05)., Conclusions: TriV pacing was associated with significant improvements in clinical and echocardiographic parameters compared with BiV pacing.

Aims: An increasing number of transseptal punctures (TSPs) are performed worldwide for atrial ablations. Transseptal punctures can be complex and can be associated with potentially life threatening complications. The purpose of the study was to evaluate the safety and efficacy of a novel transseptal guidewire (TSGW) designed to facilitate TSPs., Methods and Results: Transseptal punctures were performed using a SafeSept TSGW passed through a standard TSP apparatus. Transseptal punctures were performed by standard technique with additional use of a TSGW allowing probing of the interatrial septum without needle exposure and penetration of the fossa into the left atrium (LA). Transseptal puncture using the TSGW was performed in 210 patients. Left atrial access was achieved successfully in 205 of 210 patients (97.6%) and in 96.3% of patients undergoing repeat TSP. Left atrial access was achieved with the first pass in 81.2% (mean 1.4 ± 0.9 passes, range 1-6) using the TSGW. No serious complications were attributable to the use of the TSGW, even in cases of failed TSP., Conclusions: The TSGW is associated with a high success rate for TSP and may be a useful alternative to transoesophageal or intracardiac echocardiogram-guided TSP.

Background: Precise mechanisms that initiate ventricular tachycardia (VT) in the intact infarcted human heart have not been defined., Objective: The purpose of this study was to investigate the mechanisms that underlie human postinfarct VT initiation., Methods: Noncontact mapping of the left ventricle was performed in 9 patients (age 67.1 +/- 7.8 years, ejection fraction 34.4% +/- 5%) with previous myocardial infarction and sustained monomorphic VT., Results: Circuits in which >/=30% of the diastolic pathway (DP) could be defined were identified in 12 VTs (cycle length 357 +/- 60 ms). Eighteen VT episodes were initiated with pacing, and one occurred spontaneously. Ten complete and two partial circuits were mapped (89% +/- 25% of the DP). In all complete circuits, pacing led to the development of unidirectional conduction block at the location of the subsequent VT exit site and the formation of functional block creating a border(s) for subsequent DP. Wavefront velocity in the DP region slowed from 1.22 +/- 0.2 m/s during sinus rhythm to 0.59 +/- 0.14 m/s during VT (P <.005). In 11 initiation episodes, lines of functional block and areas of slow conduction developed progressively over one to six reentrant cycles before a stable DP was established and sustained monomorphic VT ensued. The formation of unidirectional or functional lines of block was not identified during identical pacing protocols that failed to initiate VT (n = 14)., Conclusion: Initiation of sustained monomorphic VT requires the development of unidirectional block and formation of lines of functional block creating borders for a DP in areas of slow conduction. A transitional stage often exists during the initiation process before a stable VT circuit is established.

We present a case of a 36-year-old woman with highly symptomatic persistent atrial fibrillation (AF) refractory to sotalol, flecainide, and external direct current (DC) cardioversion. The patient underwent biatrial mapping and ablation procedure for AF. Both atria were characterized by refractory properties which were much shorter than reported previously. Global fibrillatory activity was present with a median cycle length of 120 ms (range: 62-143). Extensive map-guided ablation sets had to be delivered to both left and right sides before effective DC cardioversion enabled sinus rhythm (SR) restoration. The patient remained in SR at 9 months of follow-up.

An increasing number of patients with congenital heart disease are surviving into adulthood and some have indications for device therapy. Complex anatomical abnormalities may hinder the operator and require the adaptation of standard implantation techniques. We present the first report of successful biventricular ICD implantation in a patient with mesocardia, congenitally corrected transposition of the great arteries, pulmonary atresia, and a left superior vena cava draining into the coronary sinus. This case posed challenges in lead placement due to both complex anatomy and the risk of inappropriate device therapies secondary to far-field oversensing.

Objectives: The purpose of this study was to examine the resetting response in human ventricular tachycardia (VT) circuits with 3-dimensional mapping., Background: In characterizing re-entry with the resetting response, inferences are made about interaction of single ventricular extrastimuli (SVE) with VT., Methods: Non-contact mapping was used to examine the effects of SVE from 25 sites on 10 infarct-related VT circuits., Results: The local temporal excitable gap (EGap) was 113.8 +/- 64.3 ms, 25.8 +/- 11.2% of VT cycle length. In 7 VT circuits there was a clear difference in the EGap at different points in the circuit. All circuits could be pre-excited over a range of SVEs, resulting in either: 1) premature activation throughout the circuit resulting in reset; 2) premature activation at entry, but subsequent interval dependent conduction slowing (IDCS) resulting in a fully compensatory return cycle; or 3) change to functional lines of block and return cycle QRS morphology. The principal determinant of whether SVE resulted in reset was the degree of IDCS within the diastolic pathway (DP) of the circuit. Resetting occurred from 9 sites (7 VT) but was absent from 15 sites despite pre-excitation of a sizeable EGap in the circuit in all cases., Conclusions: In infarct-related VT, all circuits can be pre-excited over a range of SVEs, the effect of which is dependent on the degree of IDCS within the DP or modification of functional block defining the circuit. Failure to reset does not therefore indicate the absence of an EGap or failure of entry to the circuit. The temporal and spatial properties of the EGap vary at different sites of entry to the circuit.

Introduction: Characteristics of the 12-lead ECG during VT are used to guide initial placement of mapping catheters in endocardial ventricular tachycardia (VT) ablation. Previously constructed algorithms for guidance in human infarct-related VT are limited to patients known to have anterior or inferior infarcts only. We hypothesized that 12-lead ECG characteristics could be used to determine VT exit site in patients with all types of infarction of unknown location., Methods and Results: From noncontact activation maps of 121 LV VT in 51 patients undergoing catheter ablation, VT exit sites were determined and correlated with ECG characteristics according to bundle branch block configuration, limb lead polarity and patterns of precordial R-wave transition. Eight ECG patterns were identified that accounted for 71% of all VT and gave a positive predictive value (PPV) > or =70% using the first two criteria. No correlation was found with patterns of R-wave transition. Using these criteria an algorithm was developed, which was then applied prospectively and blinded to a further 17 VT in 11 patients. Of the 15 VT (88%) to which the algorithm predicted an exit site location (with a PPV > or =70%), 14 VT (93%) were correctly predicted by the algorithm., Conclusion: This algorithm can be used to predict endocardial LV VT exit site location in patients undergoing catheter ablation of VT without knowledge of or reference to infarct location, and can be applied to patients with posterior and/or multiple sites of infarction.