Cardiac channelopathies are inherited cardiac disorders associated with potentially life-threatening ventricular arrhythmias. They are caused by genetic mutations of ion channels that alter cardiac cell membrane potential and intracellular haemostasis, and include long QT syndromes (LQTSs), Brugada syndrome and the much rarer catecholaminergic polymorphic ventricular tachycardia, idiopathic ventricular fibrillation, short QT syndrome and early repolarization syndrome. Presentation of these varies widely from sudden cardiac death to incidental diagnosis at the time of electrocardiography. While they are rare, diagnosis and subsequent familial screening can have significant results for both the index patient and family members. A clear understanding of the cardiac action potential helps to clarify the pathological mechanism of arrhythmogenesis that characterizes these conditions. Risk stratification of adverse outcomes from these conditions is complex and often imprecise. Medical therapy and implantable cardioverter-defibrillators have a potential role in patient management. It is recommended that complex decisions relating to these patients be discussed in a multidisciplinary team environment wherever possible. Most of this review focuses on LQTS and Brugada syndrome as these are the most common forms of cardiac channelopathies.

Abstract Funding Acknowledgements Type of funding sources: None. Background Pulmonary vein (PV) isolation is the cornerstone of atrial fibrillation (AF) management. However, AF recurrence is extremely common after a single procedure. The CLOSE protocol, which is the standardisation of radiofrequency catheter ablation by delivering a point-by-point lesion set defined by ablation index (AI), has demonstrated 80% freedom of AF. Yet PV reconnection is still up to 38% in these patients (1). A small decrease in generator impedance (GI), which is not part of the AI algorithm, has been associated with recovery of PV conduction. Purpose The study aimed to identify whether lesions having a poor impedance drop (PID) after wide area circumferential ablation (WACA) are associated with PV reconnection, despite adopting to the CLOSE protocol. Methods 120 consecutive patients who had both the index (i-AFA) and redo AF ablations (r-AFA) due to AF recurrence at our centre from Jan 2018 to Jun 2021 were screened. 18 patients who had WACA around PVs using high power (40 to 50W) with a minimum AI of 400, whilst adhering the CLOSE protocol during the i-AFA, and who had evidence of PV reconnection during r-AFA, were included in the study. Ones who had left atrial (LA) substrate or cryoablation were excluded. GI was measured between the skin patch and ablation catheter. CARTO® system was used to create LA electroanatomical maps (EAMs) and register ablation lesions. Each WACA around PVs was divided into eight anatomical segments (Figure). PID was defined as an impedance change of <8Ω, based on previous studies (2). These lesions were identified and categorised to the relevant anatomical segment in the i-AFA. Locations of the discrete ablation lesions that re-isolated PVs during the r-AFA, were used as a surrogate to denote areas of PV reconnection. These were also spatially matched to the relevant anatomical segment. Each EAM was reviewed by two electrophysiologists. Results 30 out of the 36 WACAs (83%) and on average, at least 2 segments per WACA (2.6; 95% confidence interval (CI): 2.2-3.1) had reconnected. 54% of the reconnected segments had at least one lesion with PID. Having a lesion with PID in a PV segment in the i-AFA was significantly associated with evidence of PV reconnection in the same segment in the r-AFA (odds ratio: 2.1 [95% CI: 1.3-3.6; p<0.01]). Right posterior/inferior (56%) and left anterior/superior (50%) PV segments were the most common areas to reconnect and these areas were also associated with a higher incidence of PID lesions in the i-AFA (94% and 67%, respectively). Conversely, 80% of segments with all lesions having an impedance drop of ≥8Ω had no PV reconnection. Conclusion Lesions with PID in the i-AFA could impact PV reconnection, despite lesion contiguity and an adequate AI. Identifying and targeting these areas of PID, in addition to the CLOSE protocol, could potentially reduce AF recurrence. Prospective studies are needed to validate this hypothesis and its safety.

Abstract Aims To determine whether triventricular (TriV) pacing is feasible and improves CRT response compared to conventional biventricular (BiV) pacing in patients with left bundle branch block (LBBB) and intermediate QRS prolongation (120–150 ms). Methods and results Between October 2015 and November 2019, 99 patients were recruited from 11 UK centres. Ninety-five patients were randomized 1:1 to receive TriV or BiV pacing systems. The primary endpoint was feasibility of TriV pacing. Secondary endpoints assessed symptomatic and remodelling response to CRT. Baseline characteristics were balanced between groups. In the TriV group, 43/46 (93.5%) patients underwent successful implantation vs. 47/49 (95.9%) in the BiV group. Feasibility of maintaining CRT at 6 months was similar in the TriV vs. BiV group (90.0% vs. 97.7%, P = 0.191). All-cause mortality was similar between TriV vs. BiV groups (4.3% vs. 8.2%, P = 0.678). There were no significant differences in echocardiographic LV volumes or clinical composite scores from baseline to 6-month follow-up between groups. Conclusion Implantation of two LV leads to deliver and maintain TriV pacing at 6 months is feasible without significant complications in the majority of patients. There was no evidence that TriV pacing improves CRT response or provides additional clinical benefit to patients with LBBB and intermediate QRS prolongation and cannot be recommended in this patient group. Clinical trial registration number Clinicaltrials.gov: NCT02529410.

BACKGROUND:Ablation of atrial arrhythmias in patients with congenital heart disease (CHD) has markedly improved with advanced mapping systems. However, recurrence rates remain high. The linear ablation strategy is not uncommonly practiced necessitating prolonged ablation times. We report the outcomes of adopting a strategy of minimal, cluster delivery of radiofrequency (RF) energy at critical substrates identified by ultrahigh-definition mapping for atrial arrhythmias in patients with CHD.METHODS:Non-cavotricuspid isthmus (non-CTI) atrial tachycardias were ablated with a targeted ablation cluster technique (TACT) using an ultrahigh-density mapping system combined with multielectrode monitoring and endpoint determination in preference to linear ablation. The arrhythmia substrates, RF times, and acute- and medium-term success rates were studied.RESULTS:Fifty-eight tachycardias were mapped and ablated in 42 procedures: 34 non-CTIs and 24 CTIs. A targeted ablation cluster was performed for non-CTI tachycardias, with a median ablation time of 3.1 min. In 53% of non-CTI tachycardias, arrhythmia termination was achieved with ≤2 RF applications. After a mean follow-up of 23.6 months, 27 (80%) patients were free of recurrent atrial arrhythmias. One of 34 targeted non-CTI tachycardia recurred, with a final success rate of 91%. Linear ablation was performed for CTI flutters with a median ablation time of 6.8 min (vs. non-CTIs, p = .006). Three of 21 tachycardias recurred due to reconnection of the ablation line but the final success rate was 100%.CONCLUSIONS:The TACT approach for non-CTI atrial arrhythmias in congenital patients as guided by the ultrahigh-density mapping is an effective method with short ablation times and excellent medium-term outcomes.

BACKGROUND:Patients who improve following cardiac resynchronization therapy (CRT) have left ventricular (LV) remodeling and improved cardiac output (CO). Effects on the systemic circulation are unknown. OBJECTIVE:To explore the effects of CRT on aortic and pulmonary blood flow and systemic afterload. METHODS:At CRT implant patients underwent a noninvasive assessment of central hemodynamics, including wave intensity analysis (n = 28). This was repeated at 6 months after CRT. A subsample (n = 11) underwent an invasive electrophysiological and hemodynamic assessment immediately following CRT. CRT response was defined as reduction in LV end-systolic volume ≥15% at 6 months. RESULTS:In CRT responders (75% of those in the noninvasive arm), there was a significant increase in CO (from 3 ± 2 L/min to 4 ± 2 L/min, P = .002) and LV dP/dtmax (from 846 ± 162 mm Hg/s to 958 ± 194 mm Hg/s, P = .001), immediately after CRT in those in the invasive arm. They demonstrated a significant increase in aortic forward compression wave (FCW) both acutely and at follow-up. The relative change in LV dP/dtmax strongly correlated with changes in the aortic FCW (R s 0.733, P = .025). CRT responders displayed a significant reduction in afterload, and a decrease in systemic vascular resistance and pulse wave velocity acutely; there was a significant decrease in acute pulmonary afterload measured by the pulmonary FCW and forward expansion wave. CONCLUSION:Improved cardiac function following CRT is attributable to a combination of changes in the cardiac and cardiovascular system. The relative importance of these 2 mechanisms may then be important for optimizing CRT.

BACKGROUND No periprocedural metric has demonstrated improved cardiac resynchronization therapy (CRT) outcomes in a multicenter setting. OBJECTIVE We sought to determine if left ventricular (LV) lead placement targeted to the coronary sinus (CS) branch generating the best acute hemodynamic response (AHR) results in improved outcomes at 6 months. METHODS In this multicenter randomized controlled trial, patients were randomized to guided CRT or conventional CRT. Patients in the guided arm had LV dP/dtmax measured during biventricular (BIV) pacing. Target CS branches were identified and the final LV lead position was the branch with the best AHR and acceptable threshold values. The primary endpoint was the proportion of patients with a reduction in LV end-systolic volume (LVESV) of >= 15% at 6 months. RESULTS A total of 281 patients were recruited across 12 centers. Mean age was 70.8 +/- 10.9 years and 54% had ischemic etiology. Seventy-three percent of patients in the guided arm demonstrated a reduction in LVESV of >= 15% at 6 months vs 60% in the conventional arm (P = .02). Patients with AHR >= 10% were more likely to demonstrate a reduction of ESV >= 15% (84% of patients with an AHR >= 10% vs 28% with an AHR < 10%; P < 0.001). Procedure duration and fluoroscopy times were longer in the pressure wire-guided arm (104 +/- 39 minutes vs 142 +/- 39 minutes; P <.001 and 20 +/- 16 minutes vs 28 +/- 15 minutes; P = .002). CONCLUSIONS AHR determined by invasively measuring LV dP/ dtmax during BIV pacing predicts reverse remodeling 6 months after CRT. Patients in whom LV dP/dtmax was used to guide LV lead placement demonstrated better rates of reverse remodeling.

Prior to ventricular tachycardia ablation, this patient's cardiac implantable electronic device (CIED) was temporarily programmed to backup pacing mode with tachycardia therapies disabled. During radiofrequency energy delivery, the patient developed ventricular fibrillation requiring emergent cardioversion. Electrogram interrogation showed that the CIED switched to noise reversion mode during ablation. The consequent asynchronous pacing resulted in a paced QRS landing on an intrinsic T wave, inducing ventricular fibrillation. This serves as an important reminder that asynchronous pacing consequent to CIED oversensing could occur in any procedure that could cause electromagnetic interference such as radiofrequency cathteter ablation.

Background: Cardiac resynchronization therapy (CRT) produces acute changes in electric resynchronization that can be measured noninvasively with electrocardiographic body surface mapping (ECGi). The relation between baseline acute electrophysiology metrics and their manipulation with CRT and reverse remodeling is unclear. Objective: To test (ECGi) derived parameters of electrical activation as predictors of volumetric response to CRT. Methods: ECGi was performed in 21 patients directly following CRT implant. Activation parameters (left ventricular total activation time [LVtat], global biventricular total activation time [VVtat], global left/right ventricular electrical synchrony [VVsync], and global left ventricular dispersion of activation times [LVdisp]) were measured at baseline and following echocardiographically optimized CRT. Remodeling response (>15% reduction left ventricular end-systolic volume) was assessed 6 months post CRT. Results: Patients were aged 68.9 ± 12.1 years, 81% were male, and 57% were ischemic. Baseline measures of dyssynchrony were more pronounced in left bundle branch block (LBBB) vs non-LBBB. ECGi demonstrated a trend of greater interventricular dyssynchrony between responders and nonresponders that did not reach statistical significance (VVsync: -45.7 ± 22.4 ms vs -25.1 ± 29.3 ms, P = .227). Remaining activation parameters were similar between responders and nonresponders (VVtat 101 ± 22.0 ms vs 98.9 ± 23.4 ms, P = .838; LVtat 86.4 ± 17.1 ms vs 85.1 ± 27.7 ms, P = .904; LVdisp 28.2 ± 6.3 ms vs 27.0 ± 8.7 ms, P = .726). In volumetric responders activation parameters were significantly improved with CRT compared to nonresponders: VV sync (-45.67 ± 22.41 ms vs 2.33±18.87 ms, P = .001), VVtat (101 ± 22.04 ms vs 71 ± 14.01 ms, P = .002), LVtat (86.44 ± 17.15 ms vs 67.67 ± 11.31 ms, P = .006), and LVdisp (28.22 ± 6.3 ms vs 21.56 ± 4.45 ms, P = .008). Conclusion: Baseline ECGi activation times did not predict CRT volumetric response. Volumetric responders exhibited significant improvements in ECGi-derived metrics with CRT. ECGi does not select CRT candidates but may be a useful adjunct to guide left ventricle lead implants and to perform postimplant CRT optimization.

Background Antitachycardia pacing (ATP), which may avoid unnecessary implantable cardioverter-defibrillator (ICD) shocks, does not always terminate ventricular arrhythmias (VAs). Mean entropy calculated using cardiac magnetic resonance texture analysis (CMR-TA) has been shown to predict appropriate ICD therapy. We examined whether scar heterogeneity, quantified by mean entropy, is associated with ATP failure and explore potential mechanisms using computer modeling. Methods A subanalysis of 114 patients undergoing CMR-TA where the primary endpoint was delivery of appropriate ICD therapy (ATP or shock therapy) was performed. Patients receiving appropriate ICD therapy (n = 33) were dichotomized into "successful ATP" versus "shock therapy" groups. In silico computer modeling was used to explore underlying mechanisms. Results A total of 16 of 33 (48.5%) patients had successful ATP to terminate VA, and 17 of 33 (51.5%) patients required shock therapy. Mean entropy was significantly higher in the shock versus successful ATP group (6.1 +/- 0.5 vs 5.5 +/- 0.7,P = .037). Analysis of patients receiving ATP (n = 22) showed significantly higher mean entropy in the six of 22 patients that failed ATP (followed by rescue ICD shock) compared to 16 of 22 that had successful ATP (6.3 +/- 0.7 vs 5.5 +/- 0.7,P = .048). Computer modeling suggested inability of the paced wavefront in ATP to successfully propagate from the electrode site through patchy fibrosis as a possible mechanism of failed ATP. Conclusions Our findings suggest lower scar heterogeneity (mean entropy) is associated with successful ATP, whereas higher scar heterogeneity is associated with more aggressive VAs unresponsive to ATP requiring shock therapy that may be due to inability of the paced wavefront to propagate through scar and terminate the VA circuit.

OBJECTIVES The aim of this study was to examine the value of first-phase ejection fraction (EF1), to predict response to cardiac resynchronization therapy (CRT) and clinical outcomes after CRT. BACKGROUND CRT is an important treatment for patients with chronic heart failure. However, even in carefully selected cases, up to 40% of patients fail to respond. EF1, the ejection fraction up to the time of maximal ventricular contraction, is a novel sensitive echocardiographic measure of early systolic function and might relate to response to CRT. METHODS An initial retrospective study was performed in 197 patients who underwent CRT between 2009 and 2018 and were followed to determine clinical outcomes at King's Health Partners in London. A validation study (n 1/4 100) was performed in patients undergoing CRT at Barts Heart Centre in London. RESULTS Volumetric response rate (reduction in end-systolic volume $15%) was 92.3% and 12.1% for those with EF1 in the highest and lowest tertiles (P < 0.001). A cutoff value of 11.9% for EF1 had >85% sensitivity and specificity for prediction of response to CRT; on multivariate binary logistic regression analysis incorporating previously defined predictors, EF1 was the strongest predictor of response (odds ratio [OR]: 1.56 per 1% change in EF1; 95% CI: 1.37-1.78; P < 0.001). EF1 was also the strongest predictor of improvement in clinical composite score (OR: 1.11; 95% CI: 1.04-1.19; P 1/4 0.001). Improvement in EF1 at 6 months after CRT implantation (6.5% +/- 5.8% vs 1.8% +/- 4.3% in responders vs nonresponders; P < 0.001) was the best predictor of heart failure rehospitalization and death after median follow-up period of 20.3 months (HR: 0.81; 95% CI: 0.73-0.90; P < 0.001). In the validation cohort, EF1 was a similarly 1strong predictor of response (OR: 1.45; 95% CI: 1.23-1.70; P < 0.001) as in the original cohort. CONCLUSIONS EF1 is a promising marker to identify patients likely to respond to CRT. (J Am Coll Cardiol Img

Abstract Purpose The conversion of synaptic glutamate to glutamine in astrocytes by glutamine synthetase (GS) is critical to maintaining healthy brain activity and may be disrupted in several brain disorders. As the GS catalysed conversion of glutamate to glutamine requires ammonia, we evaluated whether [13N]ammonia positron emission tomography (PET) could reliability quantify GS activity in humans. Methods In this test–retest study, eight healthy volunteers each received two dynamic [13N]ammonia PET scans on the morning and afternoon of the same day. Each [13N]ammonia scan was preceded by a [15O]water PET scan to account for effects of cerebral blood flow (CBF). Results Concentrations of radioactive metabolites in arterial blood were available for both sessions in five of the eight subjects. Our results demonstrated that kinetic modelling was unable to reliably distinguish estimates of the kinetic rate constant k 3 (related to GS activity) from K 1 (related to [13N]ammonia brain uptake), and indicated a non-negligible back-flux of [13N] to blood (k 2). Model selection favoured a reversible one-tissue compartmental model, and [13N]ammonia K 1 correlated reliably (r 2 = 0.72–0.92) with [15O]water CBF. Conclusion The [13N]ammonia PET method was unable to reliably estimate GS activity in the human brain but may provide an alternative index of CBF.

It is uncertain whether right ventricular (RV) lead position in cardiac resynchronization therapy impacts response. There has been little detailed analysis of the activation patterns in RV septal pacing (RVSP), especially in the CRT population. We compare left bundle branch block (LBBB) activation patterns with RV pacing (RVP) within the same patients with further comparison between RV apical pacing (RVAP) and RVSP. Body surface mapping was undertaken in 14 LBBB patients after CRT implantation. Nine patients had RVAP, 5 patients had RVSP. Activation parameters included left ventricular total activation time (LVtat), biventricular total activation time (VVtat), interventricular electrical synchronicity (VVsync), and dispersion of left ventricular activation times (LVdisp). The direction of activation wave front was also compared in each patient (wave front angle (WFA)). In silico computer modelling was applied to assess the effect of RVAP and RVSP in order to validate the clinical results. Patients were aged 64.6 ± 12.2 years, 12 were male, 8 were ischemic. Baseline QRS durations were 157 ± 18 ms. There was no difference in VVtat between RVP and LBBB but a longer LVtat in RVP (102.8 ± 19.6 vs. 87.4 ± 21.1 ms, p = 0.046). VVsync was significantly greater in LBBB (45.1 ± 20.2 vs. 35.9 ± 17.1 ms, p = 0.01) but LVdisp was greater in RVP (33.4 ± 5.9 vs. 27.6 ± 6.9 ms, p = 0.025). WFA did rotate clockwise with RVP vs. LBBB (82.5 ± 25.2 vs. 62.1 ± 31.7 op = 0.026). None of the measurements were different to LBBB with RVSP; however, the differences were preserved with RVAP for VVsync, LVdisp, and WFA. In silico modelling corroborated these results. RVAP activation differs from LBBB where RVSP appears similar. (ClinicalTrials.gov identifier: NCT01831518)

AIMS Transvenous lead extraction (TLE) may be necessary due to system infection/erosion or lead malfunction. Cardiac resynchronization therapy (CRT) patients undergoing TLE may be at greater risk due to increased comorbidities. We examined whether patients with CRT systems undergoing TLE had more comorbidities and higher 30-day mortality than those with non-CRT devices. METHODS AND RESULTS All TLEs between October 2000 and December 2016 were prospectively collected. During this period 925 TLEs occurred (CRT group 231, non-CRT group 694). Cardiac resynchronization therapy patients were older (68.1 ± 10.8 years vs. 64.3 ± 16.1 years, P = 0.024); more likely male (85.7% vs. 69%, P < 0.001); had lower mean left ventricular ejection fraction (34.1 ± 12.7% vs. 48.3 ± 12.9%, P < 0.001); had higher prevalence of renal impairment (33.8% vs. 13.7%, P < 0.001) and were more likely to have ≥2 comorbidities (84% vs. 40.1%, P < 0.001). Mean lead dwell time was lower in the CRT group (5.6 ± 5.5 years vs. 7.6 ± 7.1 years, P = 0.002). There was no significant difference in all-cause 30-day mortality rates between CRT (3.0%, n = 7) and non-CRT patients (2.0%, n = 14) (P = 0.443). The majority of deaths in both groups were due to sepsis. Univariate and multivariate analysis showed age, renal impairment and sepsis were associated with increased risk of 30-day mortality. Transvenous lead extraction of a CRT system did not predict 30-day mortality. CONCLUSION Transvenous lead extraction in CRT patients was not associated with increased 30-day mortality when compared with non-CRT patients. Age, renal impairment and sepsis were independent predictors of 30-day mortality. Sepsis was the main cause of 30-day mortality.

OBJECTIVES A new etectroanatomic mapping system (Rhythmia, Boston Scientific, Marlborough, Massachusetts) using a 64-electrode mapping basket is now available; we systematically assessed its use in complex congenital heart disease (CHD). BACKGROUND The incidence of atrial arrhythmias post-surgery for CHD is high. Catheter ablation has emerged as an effective treatment, but is hampered by limitations in the mapping system's ability to accurately define the tachycardia circuit. METHODS Mapping and ablation data of 61 patients with CHD (35 mates, age 45 +/- 14 years) from 8 tertiary centers were reviewed. RESULTS Causes were as follows: Transposition of Great Arteries (atrial switch) (n = 7); univentricutar physiology (Fontans) (n = 8); Tetralogy of Fattot (n = 10); atrial septat defect (ASD) repair (n = 15); tricuspid valve (TV) anomalies (n = 10); and other (n = 11). The total number of atrial arrhythmias was 86. Circuits were predominantly around the tricuspid valve (n = 37), atriotomy scar (n = 10), or ASD patch (n = 4). Although the majority of peri-tricuspid circuits were cavo-tricuspid-isthmus dependent (n = 30), they could follow a complex route between the annulus and septat resection, ASD patch, coronary sinus, or atriotomy. Immediate ablation success was achieved in all but 2 cases; with follow-up of 12 +/- 8 months, 7 patients had recurrence. CONCLUSIONS We demonstrate the feasibility of the basket catheter for mapping complex CHD arrhythmias, including with transbaffle and transhepatic access. Although the circuits often involve predictable anatomic landmarks, the precise critical isthmus is often difficult to predict empirically. Ultra-high-density mapping enables elucidation of circuits in this complex anatomy and allows successful treatment at the isthmus with a minimal lesion set. (C) 2019 by the American College of Cardiology Foundation.

INTRODUCTION:Cardiac resynchronisation therapy (CRT) corrects electrical dyssynchrony. However, the temporal changes in the electrical timing according to substrate are unclear. We used electrocardiographic imaging (ECGi) for serial non-invasive assessment of the underlying electrical substrate and its response to resynchronisation. MATERIAL AND METHODS:ECGi activation maps were constructed 1 day and 6 months post CRT implant. ECGi maps were analysed offline to determine the total ventricular activation time (TVaT) and the time for the bulk of ventricular activation (10th to 90th percentile activation; VaT10-90 Index). Statistical analysis was performed using repeated measures ANOVA with post-hoc pairwise comparisons using paired t-tests. The % relative change within each time point was also calculated and compared between the two time points. RESULTS:Eleven CRT patients were studied. Both total and bulk ventricular activation significantly decreased with CRT turned ON at day 1. Intrinsic (CRT OFF) TVaT and VaT10-90 Index at day 1 were 143 ± 23 and 84 ± 20 ms, respectively, and they significantly decreased post CRT to 115 ± 26 ms (P < 0.001) and 49 ± 17 ms (P < 0.05), respectively. The relative change at day 1 was also statistically significant for TVaT (19 ± 12%, P < 0.001) and VaT10-90 Index (39 ± 25%, P < 0.001). After 6 months, the relative decrease in TVaT with CRT ON remained stable (19% vs. 18% at day 1 and 6 months, respectively) whereas reduction the in VaT10-90 Index was decreased 39% vs. 26% at day 1 and 6 months, respectively. In non-ischaemic patients both total and bulk activation times reduced following CRT. Volumetric responders exhibited an electrical remodelling for bulk activation not apparent in Non-responders, after 6 months of CRT ON. CONCLUSIONS:Intrinsic bulk myocardium activation becomes more rapid and synchronous with CRT. The bulk activation time is more susceptible to improvement by CRT in ischaemic patients and volumetric responders. These observations are consistent with CRT causing reverse electrophysiological remodelling in the bulk myocardium, but not in late-activating ischaemic or fibrotic regions.

BACKGROUND Enhanced beat-to-beat variability of repolarization is strongly linked to arrhythmogenesis and is largely due to variation in ventricular action potential duration (APD). Previous studies in humans have relied on QT interval measurements; however, a direct relationship between beat-to-beat variability of APD and arrhythmogenesis in humans has yet to be demonstrated. OBJECTIVE This study aimed to explore the beat-to-beat repolarization dynamics in patients with heart failure at the level of ventricular APD. METHODS Forty-three patients with heart failure and implanted cardiac resynchronization therapy -defibrillator devices were studied. Activation-recovery intervals as a surrogate for APD were recorded from the left ventricular epicardial lead while pacing from the right ventricular lead to maintain a constant cycle length. RESULTS During a mean follow-up of 23.6 +/- 613.6 months, 11 patients sustained ventricular fibrillation/ventricular tachycardia (VT/VF) and received appropriate implantable cardioverter-defibrillator therapies (antitachycardia pacing or shock therapy). Activation-recovery interval variability (ARIV) was significantly greater in patients with subsequent VT/VF than in those without VT/VF (3.55 +/- 1.3 ms vs 2.77 +/- 1.09 ms; P=.047). Receiver operating characteristic curve analysis (area under the curve 0.71; P=.046) suggested high-and low-risk ARIV groups for VT/VF. Kaplan-Meier survival analysis demonstrated that the time until first appropriate therapy for VT/VF was significantly shorter in the high-risk ARIV group (P=.028). ARIV was a predictor for VT/VF in the multivariate Cox model (hazard ratio 1.623; 95% confidence interval 1.1-2.393; P=.015). CONCLUSION Increased left ventricular ARIV is associated with an increased risk of VT/VF in patients with heart failure.

Despite medical advancements, the prognosis of patients with heart failure remains poor. While echocardiography and cardiac magnetic resonance imaging remain at the forefront of diagnosing and monitoring patients with heart failure, cardiac computed tomography (CT) has largely been considered to have a limited role. With the advancements in scanner design, technology, and computer processing power, cardiac CT is now emerging as a valuable adjunct to clinicians managing patients with heart failure. In the current manuscript, we review the current applications of cardiac CT to patients with heart failure and also the emerging areas of research where its clinical utility is likely to extend into the realm of treatment, procedural planning, and advanced heart failure therapy implementation.

Study hypothesis. We sought to investigate the association between echocardiographic optimisation and ventricular activation time in cardiac resynchronisation therapy (CRT) patients, obtained through the use of electrocardiographic mapping (ECM). We hypothesised that echocardiographic optimisation of the pacing delay between the atrial and ventricular leadsatrioventricular delay (AVD)and the delay between ventricular leadsinterventricular pacing interval (VVD)would correlate with reductions in ventricular activation time. Background. Optimisation of AVD and VVD may improve CRT patient outcome. Optimal delays are currently set based on echocardiographic indices; however, acute studies have found that reductions in bulk ventricular activation time correlate with improvements in acute haemodynamic performance. Materials and methods. Twenty-one patients with established CRT criteria were recruited. After implantation, patients underwent echo-guided optimisation of the AVD and VVD. During this procedure, the participants also underwent noninvasive ECM. ECM maps were constructed for each AVD and VVD. ECM maps were analysed offline. Total ventricular activation time (TVaT) and a ventricular activation time index (VaT(10-90)) were calculated to identify the optimal AVD and VVD timings that gave the minimal TVaT and VaT(10-90) values. We correlated cardiac output with these electrical timings. Results. Echocardiographic programming optimisation was not associated with the greatest reductions in biventricular activation time (VaT(10-90) and TVaT). Instead, bulk activation times were reduced by a further 20% when optimised with ECM. A significant inverse correlation was identified between reductions in bulk ventricular activation time and improvements in LVOT VTI (p<0.001), suggesting that improved ventricular haemodynamics are a sequelae of more rapid ventricular activation. Conclusions. EAM-guided programming optimisation may achieve superior fusion of activation wave fronts leading to improvements in CRT response.

Aims The decision to abandon or extract superfluous leads remains controversial. We sought to compare procedural outcome of patients with and without abandoned leads undergoing transvenous lead extraction (TLE). Methods and results An analysis of the ESC-EHRA European Lead Extraction ConTRolled ELECTRa registry was conducted. Patients were stratified into two groups based on the presence (Group 1) or absence (Group 2) of abandoned leads at the time for extraction. Out of 3508 TLE procedures, 422 patients (12.0%) had abandoned leads (Group 1). Group 1 patients were older and more likely to have implantable cardioverter-defibrillator devices, infection indication (78.8% vs. 49.8%), and vegetations (24.6% vs. 15.3%). Oldest lead dwelling time was longer in Group 1 (10.9 vs. 6.3years) as was the number of extracted leads per patient (3.2 vs. 1.7). Manual traction failure (94.5% vs. 78.8%), powered sheath use (50.7% vs. 28.4%), and femoral approach were higher in Group 1 (P<0.0001). Procedural success rate and clinical success (89.8% vs. 96.6%, P<0.0001) were lower in Group 1. Major complication including deaths (5.5% vs. 2.3%, P=0.0007) and procedure related major complications (3.3% vs. 1.4%, P=0.0123) were higher in Group 1. The presence of abandoned leads at the time of TLE was an independent predictor of clinical failure [odds ratio (OR) 2.31, confidence interval (CI) 1.57-3.40] and complications [OR 1.69, CI 1.22-2.35](.) receiver-operating characteristic curve analysis showed a dwell time threshold of 9years for radiological failure and major complications. Conclusions Previously abandoned leads at the time of TLE were associated with increased procedural complexity, clinical failure, and major complication, which may have important implications for future studies regarding managing of lead failures.