Blood groups and Rhesus status as potential predictors of outcomes in patients with cardiac resynchronisation therapy.

Cardiac resynchronisation therapy (CRT) improves prognosis in patients with heart failure (HF) however the role of ABO blood groups and Rhesus factor are poorly understood. We hypothesise that blood groups may influence clinical and survival outcomes in HF patients undergoing CRT. A total of 499 patients with HF who fulfilled the criteria for CRT implantation were included. Primary outcome of all-cause mortality and/or heart transplant/left ventricular assist device was assessed over a median follow-up of 4.6 years (IQR 2.3-7.5). Online repositories were searched to provide biological context to the identified associations. Patients were divided into blood (O, A, B, and AB) and Rhesus factor (Rh-positive and Rh-negative) groups. Mean patient age was 66.4 ± 12.8 years with a left ventricular ejection fraction of 29 ± 11%. There were no baseline differences in age, gender, and cardioprotective medication. In a Cox proportional hazard multivariate model, only Rh-negative blood group was associated with a significant survival benefit (HR 0.68 [0.47-0.98], p = 0.040). No association was observed for the ABO blood group (HR 0.97 [0.76-1.23], p = 0.778). No significant interaction was observed with prevention, disease aetiology, and presence of defibrillator. Rhesus-related genes were associated with erythrocyte and platelet function, and cholesterol and glycated haemoglobin levels. Four drugs under development targeting RHD were identified (Rozrolimupab, Roledumab, Atorolimumab, and Morolimumab). Rhesus blood type was associated with better survival in HF patients with CRT. Further research into Rhesus-associated pathways and related drugs, namely whether there is a cardiac signal, is required.

The Role of Risk Factor Modification in Atrial Fibrillation: Outcomes in Catheter Ablation.

The management of atrial fibrillation has evolved significantly over the last ten years with advancements in medical and catheter ablation approaches, but these have limited success when used in isolation. Trends in the management of lifestyle modifications have surfaced, as it is now better understood that modifiable risk factors contribute significantly to the development and propagation of atrial fibrillation, as well as failure of treatment. International guidelines have integrated the role of lifestyle modification in the management of atrial fibrillation and specifically in the persistent form of atrial fibrillation; these guidelines must be addressed prior to considering catheter ablation. Effective risk factor modification is critical in increasing the likelihood of an arrhythmia-free survival following catheter ablation.

A cluster of inappropriate shocks in a pediatric S-ICD patient - how to troubleshoot?

We present the case of a 16-year-old male pediatric patient diagnosed with hypertrophic cardiomyopathy (HCM, identified as having a high risk of sudden cardiac death (SCD), who underwent a successful subcutaneous implantable cardiac defibrillator (S-ICD) implantation as a primary prevention measure in 2018. His past medical history included ADHD, Autism, and panic attacks. The patient experienced appropriate shocks that successfully terminated VF episodes. However, he also experienced multiple inappropriate shocks from the S-ICD, triggered by anxiety-induced tachycardia during panic episodes. Meticulous assessment of S-ICD tracings and electrocardiograms (ECGs) revealed the erroneous classification of sinus tachycardia as sustained ventricular tachycardia, leading to unwarranted therapeutic interventions. Clinical intervention involved reprogramming of the S-ICD, emphasizing the pivotal role of personalized device configuration in pediatric cases where fine margins matter. While literature on S-ICD use in pediatric populations remains limited, emerging registries underscore the efficacy and safety of S-ICDs in preventing sudden cardiac death while reducing complications associated with intravascular leads. This case underscores the critical nature of customized device programming in pediatric patients, underscoring S-ICDs as a practical defibrillation alternative that addresses distinct concerns within this cohort of patients.

Atrial fibrillation cryoablation is an effective day case treatment: the UK PolarX vs. Arctic Front Advance experience.

AIMS: Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation for atrial fibrillation (AF). There are limited data on the PolarX Cryoballoon. The study aimed to establish the safety, efficacy, and feasibility of same day discharge for Cryoballoon PVI. METHODS AND RESULTS: Multi-centre study across 12 centres. Procedural metrics, safety profile, and procedural efficacy of the PolarX Cryoballoon with the Arctic Front Advance (AFA) Cryoballoon were compared in a cohort large enough to provide definitive comparative data. A total of 1688 patients underwent PVI with cryoablation (50% PolarX and 50% AFA). Successful PVI was achieved with 1677 (99.3%) patients with 97.2% (n = 1641) performed as day case procedures with a complication rate of <1%. Safety, procedural metrics, and efficacy of the PolarX Cryoballoon were comparable with the AFA cohort. The PolarX Cryoballoon demonstrated a nadir temperature of -54.6 ± 7.6°C, temperature at 30 s of -38.6 ± 7.2°C, time to -40°C of 34.1 ± 13.7 s, and time to isolation of 49.8 ± 33.2 s. Independent predictors for achieving PVI included time to reach -40°C [odds ratio (OR) 1.34; P < 0.001] and nadir temperature (OR 1.24; P < 0.001) with an optimal cut-off of ≤34 s [area under the curve (AUC) 0.73; P < 0.001] and nadir temperature of ≤-54.0°C (AUC 0.71; P < 0.001), respectively. CONCLUSIONS: This large-scale UK multi-centre study has shown that Cryoballoon PVI is a safe, effective day case procedure. PVI using the PolarX Cryoballoon was similarly safe and effective as the AFA Cryoballoon. The cryoablation metrics achieved with the PolarX Cryoballoon were different to that reported with the AFA Cryoballoon. Modified cryoablation targets are required when utilizing the PolarX Cryoballoon.

A randomized sham-controlled study of pulmonary vein isolation in symptomatic atrial fibrillation (The SHAM-PVI study): Study design and rationale.

INTRODUCTION: Pulmonary vein (PV) isolation has been shown to reduce atrial fibrillation (AF) burden and symptoms in patients. However, to date previous studies have been unblinded raising the possibility of a placebo effect to account for differences in outcomes. HYPOTHESIS & METHODS: The objective of this study is to compare PV isolation to a sham procedure in patients with symptomatic AF. The SHAM-PVI study is a double blind randomized controlled clinical trial. 140 patients with symptomatic paroxysmal or persistent AF will be randomized to either PV isolation (with cryoballoon ablation) or a sham procedure (with phrenic nerve pacing). All patients will receive an implantable loop recorder. The primary outcome is total AF burden at 6 months postrandomisation (excluding the 3 month blanking period). Key secondary outcomes include (1) time to symptomatic and asymptomatic atrial tachyarrhythmia (2) total atrial tachyarrhythmia episodes and (3) patient reported outcome measures. RESULTS: Enrollment was initiated in January 2020. Through April 2023 119 patients have been recruited. Results are expected to be disseminated in 2024. CONCLUSION: This study compares PV isolation using cryoablation to a sham procedure. The study will estimate the effect of PV isolation on AF burden.

The value of functional substrate mapping in ventricular tachycardia ablation.

In the setting of structural heart disease, ventricular tachycardia (VT) is typically associated with a re-entrant mechanism. In patients with hemodynamically tolerated VTs, activation and entrainment mapping remain the gold standard for the identification of the critical parts of the circuit. However, this is rarely accomplished, as most VTs are not hemodynamically tolerated to permit mapping during tachycardia. Other limitations include noninducibility of arrhythmia or nonsustained VT. This has led to the development of substrate mapping techniques during sinus rhythm, eliminating the need for prolonged periods of mapping during tachycardia. Recurrence rates following VT ablation are high; therefore, new mapping techniques for substrate characterization are required. Advances in catheter technology and especially multielectrode mapping of abnormal electrograms has increased the ability to identify the mechanism of scar-related VT. Several substrate-guided approaches have been developed to overcome this, including scar homogenization and late potential mapping. Dynamic substrate changes are mainly identified within regions of myocardial scar and can be identified as local abnormal ventricular activities. Furthermore, mapping strategies incorporating ventricular extrastimulation, including from different directions and coupling intervals, have been shown to increase the accuracy of substrate mapping. The implementation of extrastimulus substrate mapping and automated annotation require less extensive ablation and would make VT ablation procedures less cumbersome and accessible to more patients.

Incidence of premature battery depletion in subcutaneous cardioverter-defibrillator patients: insights from a multicenter registry.

BACKGROUND: The subcutaneous ICD established its role in the prevention of sudden cardiac death in recent years. The occurrence of premature battery depletion in a large subset of potentially affected devices has been a cause of concern. The incidence of premature battery depletion has not been studied systematically beyond manufacturer-reported data. METHODS: Retrospective data and the most recent follow-up data on S-ICD devices from fourteen centers in Europe, the US, and Canada was studied. The incidence of generator removal or failure was reported to investigate the incidence of premature S-ICD battery depletion, defined as battery failure within 60 months or less. RESULTS: Data from 1054 devices was analyzed. Premature battery depletion occurred in 3.5% of potentially affected devices over an observation period of 49 months. CONCLUSIONS: The incidence of premature battery depletion of S-ICD potentially affected by a battery advisory was around 3.5% after 4 years in this study. Premature depletion occurred exclusively in devices under advisory. This is in line with the most recently published reports from the manufacturer. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04767516 .

PolarX Cryoballoon metrics predicting successful pulmonary vein isolation: targets for ablation of atrial fibrillation.

AIM: Evaluate the novel PolarX Cryoballoon in atrial fibrillation (AF) catheter ablation through a propensity-matched comparison with the Arctic Front Advance (AFA). The aim was also to identify cryoablation metrics that are predictive of successful pulmonary vein isolation (PVI) with the PolarX Cryoballoon. METHODS AND RESULTS: This prospective multi-centre study included patients that underwent cryoablation for AF. All patients underwent PVI with reconnection assessed after a 30-min waiting period and adenosine. Safety, efficacy, and cryoablation metrics were compared between PolarX and a propensity-matched AFA cohort. Seventy patients were included with 278 veins treated. In total, 359 cryoablations were performed (1.3 ± 0.6 per vein) to achieve initial PVI with 205 (73.7%) veins isolating with a single cryoablation. Independent predictors for achieving initial PVI included temperature at 30 s [odds ratio (OR) 1.26; P = 0.003] and time to reach -40°C (OR 1.88; P < 0.001) with an optimal cut-off of ≤-38.5°C at 30 s [area under the curve (AUC) 0.79; P < 0.001] and ≤-40°C at ≤32.5 s (AUC 0.77; P < 0.001), respectively. Of the 278 veins, 46 (16.5%) veins showed acute reconnection. Temperature at 30 s (≤-39.5°C, OR 1.24; P = 0.002), nadir temperature (≤-53.5°C, OR 1.35; P = 0.003), and time to isolation (≤38.0 s, OR 1.18; P = 0.009) were independent predictors of sustained PVI. Combining two of these three targets was associated with reconnection in only 2-5% of PVs. Efficacy and safety of the PolarX Cryoballoon were comparable to AFA Cryoballoon, however, cryoablation metrics were significantly different. CONCLUSIONS: The PolarX Cryoballoon has a different cryoablation profile to AFA Cryoballoon. Prospective testing of these proposed targets in large outcomes studies is required.

Initial experience of the High-Density Grid catheter in patients undergoing catheter ablation for atrial fibrillation.

PURPOSE: A significant proportion of patients undergoing catheter ablation for atrial fibrillation (AF) experience arrhythmia recurrence. This is mostly due to pulmonary vein reconnection (PVR). Whether mapping using High-Density Wave (HDW) technology is superior to standard bipolar (SB) configuration at detecting PVR is unknown. We aimed to evaluate the efficacy of HDW technology compared to SB mapping in identifying PVR. METHODS: High-Density (HD) multipolar Grid catheters were used to create left atrial geometries and voltage maps in 36 patients undergoing catheter ablation for AF (either due to recurrence of an atrial arrhythmia from previous AF ablation or de novo AF ablation). Nineteen SB maps were also created and compared. Ablation was performed until pulmonary vein isolation was achieved. RESULTS: Median time of mapping with HDW was 22.3 [IQR: 8.2] min. The number of points collected with HDW (13299.6±1362.8 vs 6952.8±841.9, p<0.001) and used (2337.3±158.0 vs 1727.5±163.8, p<0.001) was significantly higher compared to SB. Moreover, HDW was able to identify more sleeves (16 for right and 8 for left veins), where these were confirmed electrically silent by SB, with significantly increased PVR sleeve size as identified by HDW (p<0.001 for both right and left veins). Importantly, with the use of HDW, the ablation strategy changed in 23 patients (64% of targeted veins) with a significantly increased number of lesions required as compared to SB for right (p=0.005) and left veins (p=0.003). CONCLUSION: HDW technology is superior to SB in detecting pulmonary vein reconnections. This could potentially result into a significant change in ablation strategy and possibly to increased success rate following pulmonary vein isolation.

Dynamic spatial dispersion of repolarization is present in regions critical for ischemic ventricular tachycardia ablation.

BACKGROUND: The presence of dynamic substrate changes may facilitate functional block and reentry in ventricular tachycardia (VT). OBJECTIVE: We aimed to study dynamic ventricular repolarization changes in critical regions of the VT circuit during sensed single extrastimulus pacing known as the Sense Protocol (SP). METHODS: Twenty patients (aged 67 ± 9 years, 17 male) underwent VT ablation. A bipolar voltage map was obtained during sinus rhythm (SR) and right ventricular SP pacing at 20 ms above ventricular effective refractory period. Ventricular repolarization maps were constructed. Ventricular repolarization time (RT) was calculated from unipolar electrogram T waves, using the Wyatt method, as the dV/dtmax of the unipolar T wave. Entrainment or pace mapping confirmed critical sites for ablation. RESULTS: The median global repolarization range (max-min RT per patient) was 166 ms (interquartile range [IQR] 143-181 ms) during SR mapping vs 208 ms (IQR 182-234) during SP mapping (P = .0003 vs intrinsic rhythm). Regions of late potentials (LP) had a longer RT during SP mapping compared to regions without LP (mean 394 ± 40 ms vs 342 ± 25 ms, P < .001). In paired regions of normal myocardium there was no significant spatial dispersion of repolarization (SDR)/10 mm2 during SP mapping vs SR mapping (SDR 11 ± 6 ms vs 10 ± 6 ms, P = .54). SDR/10 mm2 was greater in critical areas of the VT circuit during SP mapping 63 ± 29 ms vs SR mapping 16 ± 9 ms (P < .001). CONCLUSION: Ventricular repolarization is prolonged in regions of LP and increases dynamically, resulting in dynamic SDR in critical areas of the VT circuit. These dynamic substrate changes may be an important factor that facilitates VT circuits.

Contemporary management of heart failure patients with reduced ejection fraction: the role of implantable devices and catheter ablation.

Heart failure (HF) is a complex clinical syndrome characterised by significant morbidity and mortality worldwide. Evidence-based therapies for the management of HF include several well-established neurohormonal antagonists and antiarrhythmic drug therapy to mitigate the onset of cardiac arrhythmia. However, the degree of rate and rhythm control achieved is often suboptimal and mortality rates continue to remain high. Implantable cardioverter-defibrillators (ICDs), cardiac resynchronization (CRT), and combined (CRT-D) therapies have emerged as integral and rapidly expanding technologies in the management of select patients with heart failure with reduced ejection fraction (HFrEF). ICDs treat ventricular arrhythmia and are used as primary prophylaxis for sudden cardiac death, while CRT resynchronizes ventricular contraction to improve left ventricular systolic function. Left ventricular assist device therapy has also been shown to provide clinically meaningful survival benefits in patients with advanced HF, and His-bundle pacing has more recently emerged as a safe, viable, and promising pacing modality for patients with CRT indication. Catheter ablation is another important and well-established strategy for managing cardiac arrhythmia in HF, demonstrating superior efficacy when compared with antiarrhythmic drug therapy alone. In this article, we provide a comprehensive and in-depth evaluation of the role of implantable devices and catheter ablation in patients with HFrEF, outlining current applications, recent advances, and future directions in practice.

Dynamic High-density Functional Substrate Mapping Improves Outcomes in Ischaemic Ventricular Tachycardia Ablation: Sense Protocol Functional Substrate Mapping and Other Functional Mapping Techniques.

Post-infarct-related ventricular tachycardia (VT) occurs due to reentry over surviving fibres within ventricular scar tissue. The mapping and ablation of patients in VT remains a challenge when VT is poorly tolerated and in cases in which VT is non-sustained or not inducible. Conventional substrate mapping techniques are limited by the ambiguity of substrate characterisation methods and the variety of mapping tools, which may record signals differently based on their bipolar spacing and electrode size. Real world data suggest that outcomes from VT ablation remain poor in terms of freedom from recurrent therapy using conventional techniques. Functional substrate mapping techniques, such as single extrastimulus protocol mapping, identify regions of unmasked delayed potentials, which, by nature of their dynamic and functional components, may play a critical role in sustaining VT. These methods may improve substrate mapping of VT, potentially making ablation safer and more reproducible, and thereby improving the outcomes. Further large-scale studies are needed.

Subcutaneous implantable cardioverter defibrillator lead displacement.

A 52-year-old gentleman with a subcutaneous implantable cardioverter defibrillator (S-ICD) implanted in 2015 for primary prevention and a background of hypertrophic cardiomyopathy presented via remote monitoring alert (Boston Scientific Latitude NXT) with an aborted charge episode. The episode showed myopotential noise with baseline wander, and an urgent outpatient follow-up was arranged. Upon investigation the S-ICD lead had retracted to the pocket of the generator via a reel mechanism, wrapping the lead around the can. This was likely to be caused by insufficient suturing of the lead collar at the base of xiphisternum. The device had automatically disabled the SmartPass filter, which does not currently have an alert mechanism. This case highlights the rare occurrence of S-ICD lead displacement and components of the SmartPass system which can provide an early warning to lead problems.

Multicenter Study of Dynamic High-Density Functional Substrate Mapping Improves Identification of Substrate Targets for Ischemic Ventricular Tachycardia Ablation.

OBJECTIVES: The goal of this study was to evaluate the role of dynamic substrate changes in facilitating conduction delay and re-entry in ventricular tachycardia (VT) circuits. BACKGROUND: The presence of dynamic substrate changes facilitate functional block and re-entry in VT but are rarely studied as part of clinical VT mapping. METHODS: Thirty patients (age 67 ± 9 years; 27 male subjects) underwent ablation. Mapping was performed with the Advisor HD Grid multipolar catheter. A bipolar voltage map was obtained during sinus rhythm (SR) and right ventricular sense protocol (SP) single extra pacing. SR and SP maps of late potentials (LP) and local abnormal ventricular activity (LAVA) were made and compared with critical sites for ablation, defined as sites of best entrainment or pace mapping. Ablation was then performed to critical sites, and LP/LAVA identified by the SP. RESULTS: At a median follow-up of 12 months, 90% of patients were free from antitachycardia pacing (ATP) or implantable cardioverter-defibrillator shocks. SP pacing resulted in a larger area of LP identified for ablation (19.3 mm2 vs. 6.4 mm2) during SR mapping (p = 0.001), with a sensitivity of 87% and a specificity of 96%, compared with 78% and 65%, respectively, in SR. CONCLUSIONS: LP and LAVA observed during the SP were able to identify regions critical for ablation in VT with a greater accuracy than SR mapping. This may improve substrate characterization in VT ablation. The combination of ablation to critical sites and SP-derived LP/LAVA requires further assessment in a randomized comparator study.

Evaluation of ECG Imaging to Map Hemodynamically Stable and Unstable Ventricular Arrhythmias.

BACKGROUND: ECG imaging (ECGI) has been used to guide treatment of ventricular ectopy and arrhythmias. However, the accuracy of ECGI in localizing the origin of arrhythmias during catheter ablation of ventricular tachycardia (VT) in structurally abnormal hearts remains to be fully validated. METHODS: During catheter ablation of VT, simultaneous mapping was performed using electroanatomical mapping (CARTO, Biosense-Webster) and ECGI (CardioInsight, Medtronic) in 18 patients. Sites of entrainment, pace-mapping, and termination during ablation were used to define the VT site of origin (SoO). Distance between SoO and the site of earliest activation on ECGI were measured using co-registered geometries from both systems. The accuracy of ECGI versus a 12-lead surface ECG algorithm was compared. RESULTS: A total of 29 VTs were available for comparison. Distance between SoO and sites of earliest activation in ECGI was 22.6, 13.9 to 36.2 mm (median, first to third quartile). ECGI mapped VT sites of origin onto the correct AHA segment with higher accuracy than a validated 12-lead ECG algorithm (83.3% versus 38.9%; P=0.015). CONCLUSIONS: This simultaneous assessment demonstrates that CardioInsight localizes VT circuits with sufficient accuracy to provide a region of interest for targeting mapping for ablation. Resolution is not sufficient to guide discrete radiofrequency lesion delivery via catheter ablation without concomitant use of an electroanatomical mapping system but may be sufficient for segmental ablation with radiotherapy.

Evaluation of the reentry vulnerability index to predict ventricular tachycardia circuits using high-density contact mapping.

BACKGROUND: Identifying arrhythmogenic sites to improve ventricular tachycardia (VT) ablation outcomes remains unresolved. The reentry vulnerability index (RVI) combines activation and repolarization timings to identify sites critical for reentrant arrhythmia initiation without inducing VT. OBJECTIVE: The purpose of this study was to provide the first assessment of RVI's capability to identify VT sites of origin using high-density contact mapping and comparison with other activation-repolarization markers of functional substrate. METHODS: Eighteen VT ablation patients (16 male; 72% ischemic) were studied. Unipolar electrograms were recorded during ventricular pacing and analyzed offline. Activation time (AT), activation-recovery interval (ARI), and repolarization time (RT) were measured. Vulnerability to reentry was mapped based on RVI and spatial distribution of AT, ARI, and RT. The distance from sites identified as vulnerable to reentry to the VT site of origin was measured, with distances <10 mm and >20 mm indicating accurate and inaccurate localization, respectively. RESULTS: The origins of 18 VTs (6 entrainment, 12 pace-mapping) were identified. RVI maps included 1012 (408-2098) (median, 1st-3rd quartiles) points per patient. RVI accurately localized 72.2% VT sites of origin, with median distance of 5.1 (3.2-10.1) mm. Inaccurate localization was significantly less frequent for RVI than AT (5.6% vs 33.3%; odds ratio 0.12; P = .035). Compared to RVI, distance to VT sites of origin was significantly larger for sites showing prolonged RT and ARI and were nonsignificantly larger for sites showing highest AT and ARI gradients. CONCLUSION: RVI identifies vulnerable regions closest to VT sites of origin. Activation-repolarization metrics may improve VT substrate delineation and inform novel ablation strategies.

A nurse-led implantable loop recorder service is safe and cost effective.

INTRODUCTION: Implantable loop recorders (ILR) are predominantly implanted by cardiologists in the catheter laboratory. We developed a nurse-delivered service for the implantation of LINQ (Medtronic; Minnesota) ILRs in the outpatient setting. This study compared the safety and cost-effectiveness of the introduction of this nurse-delivered ILR service with contemporaneous physician-led procedures. METHODS: Consecutive patients undergoing an ILR at our institution between 1st July 2016 and 4th June 2018 were included. Data were prospectively entered into a computerized database, which was retrospectively analyzed. RESULTS: A total of 475 patients underwent ILR implantation, 271 (57%) of these were implanted by physicians in the catheter laboratory and 204 (43%) by nurses in the outpatient setting. Six complications occurred in physician-implants and two in nurse-implants (P = .3). Procedural time for physician-implants (13.4 ± 8.0 minutes) and nurse-implants (14.2 ± 10.1 minutes) were comparable (P = .98). The procedural cost was estimated as £576.02 for physician-implants against £279.95 with nurse-implants, equating to a 57.3% cost reduction. In our center, the total cost of ILR implantation in the catheter laboratory by physicians was £10 513.13 p.a. vs £6661.55 p.a. with a nurse-delivered model. When overheads for running, cleaning, and maintaining were accounted for, we estimated a saving of £68 685.75 was performed by moving to a nurse-delivered model for ILR implants. Over 133 catheter laboratory and implanting physician hours were saved and utilized for other more complex procedures. CONCLUSION: ILR implantation in the outpatient setting by suitably trained nurses is safe and leads to significant financial savings.