Ablation Targets Research Articles

Evaluation of temperature dependent vortex pinning properties in strongly pinned YBa2Cu3O7-δ thin films with Y2BaCuO5 nanoinclusions

The pinning of quantized magnetic vortices in superconducting YBa2Cu3O7- δ(YBCO or Y123) thin films with Y2BaCuO5 (Y211) nanoinclusions have been investigated over wide temperature range (4.2–77 K). The concentration of Y211 nanoinclusions has been systematically varied inside YBCO thin films prepared by laser ablation technique using surface modified target approach. Large pinning force density values (Fp ∼ 0.5 TNm−3 at 4.2 K, 9 T) have been observed for the YBCO film with moderate concentration of Y211 nanoinclusions (3.6 area % on ablation target). In addition, uniform enhancement in critical current density (Jc) was observed in the angular dependent Jc measurement of YBCO+Y211 nanocomposite films. Y211 nanoinclusions have been found to be very efficient in pinning the quantized vortices thereby enhancing the in-field Jc values over a wide range of temperature. Increasing the concentration of Y211 secondary phase into Y123 film matrix results into agglomeration of Y211 phase and observed as increased Y211 nanoparticle size. These larger secondary phase nanoparticles are not as efficient pinning centers at lower temperatures as they are at higher temperatures due to substantial reduction of the coherence length at lower temperatures. Investigation of the temperature dependence of Jc for YBCO+Y211 nanocomposite films has been conducted and possible vortex pinning mechanism in these nanocomposite films has been discussed.

Subjective identification and ablation of drivers improves rhythm control in patients with persistent atrial fibrillation. The CHAOS-AF study

Introduction and objectivesThe optimal approach for persistent atrial fibrillation (AF) ablation remains unknown. In patients with persistent AF, we compared an ablation strategy based on pulmonary vein isolation (PVI) plus ablation of drivers (PVI+D), with a conventional PVI-only approach performed in a 1:1 propensity score-matched cohort. MethodsDrivers were subjectively identified using conventional high-density mapping catheters (IntellaMap ORION, PentaRay NAV or Advisor HD Grid), without dedicated software, as fractionated continuous or quasicontinuous electrograms on 1 to 2 adjacent bipoles, which were ablated first; and as sites with spatiotemporal dispersion (the entire cycle length comprised within the mapping catheter) plus noncontinuous fractionation, which were only targeted in patients without fractionated continuous electrograms, or without AF conversion after ablation of fractionated continuous electrograms. Ablation included PVI plus focal or linear ablation targeting drivers. ResultsA total of 50 patients were included in each group (61±10 years, 25% women). Fractionated continuous electrograms were found and ablated in 21 patients from the PVI+D group (42%), leading to AF conversion in 7 patients. In the remaining 43 patients, 143 sites with spatiotemporal dispersion plus noncontinuous fractionation were targeted. Globally, AF conversion was achieved in 21 patients (42%). The PVI+D group showed lower atrial arrhythmia recurrences at 1 year of follow-up (30.6% vs 48%; P=.048) and at the last follow-up (46% vs 72%; P=.013), and less progression to permanent AF (10% vs 40%; P=.001). ConclusionsSubjective identification and ablation of drivers, added to PVI, increased 1-year freedom from atrial arrhythmia and decreased long-term recurrences and progression to permanent AF.

Pulsed Field Mapping of Ventricular Tachycardia: Verifying the Ablation Target at a Critical Location

Pulsed Field Mapping of Ventricular Tachycardia: Verifying the Ablation Target at a Critical Location

Radiofrequency Catheter Septal Ablation via a Trans-Atrial Septal Approach Guided by Intracardiac Echocardiography in Hypertrophic Obstructive Cardiomyopathy: One-Year Follow-Up.

Percutaneous radiofrequency catheter ablation (RFA) in hypertrophic obstructive cardiomyopathy (HOCM) with intracardiac echocardiography (ICE) guidance is a novel method that has been proven to be safe and effective in a small sample size study. RFA of the interventricular septum through a trans-atrial septal approach in HOCM patients with a longer follow-up has not been reported. 62 consecutive patients from March 2019 to February 2022 were included in this study. The area between the hypertrophied septum and anterior mitral valve (MV) leaflet was established using the three-dimensional system (CARTO 3 system), and all patients received atrial septal puncture under the guidance of intracardiac echocardiography (ICE). Point-by-point ablation was performed to cover the contact area. After ablation, the patients were followed up for 1, 3, 6, and 12 months. Transthoracic echocardiography was performed at 1, 3, 6, and 12 months, and resting and exercise-provoked left ventricular outflow tract (LVOT) gradients were obtained. During the 1-year follow-up, most patients' symptoms improved. The NYHA grading of the patient decreased from 2 (2, 3) at baseline to 2 (1, 2) (p 0.001). LVOT peak gradient at rest was decreased from 59 ( 27) mmHg to 30 ( 24) mmHg (p 0.001), and the provoked peak gradient was decreased from 99 ( 33) mmHg to 59 ( 34) mmHg (p 0.001). The average maximum septal thickness was reduced from 21 ( 4) mm to 19 ( 4) mm (p 0.001). After a 1-year follow-up, ice-guided radiofrequency ablation for HOCM might be a safe, accurate, and effective method. The catheter might be reliably attached to the ablation target area via trans-atrial septal access.

Non-invasive detection of slow conduction with cardiac magnetic resonance imaging for ventricular tachycardia ablation.

Non-invasive myocardial scar characterization with cardiac magnetic resonance (CMR) has been shown to accurately identify conduction channels and can be an important aid for ventricular tachycardia (VT) ablation. A new mapping method based on targeting deceleration zones (DZs) has become one of the most commonly used strategies for VT ablation procedures. The aim of the study was to analyse the capability of CMR to identify DZs and to find predictors of arrhythmogenicity in CMR channels. Forty-four consecutive patients with structural heart disease and VT undergoing ablation after CMR at a single centre (October 2018 to July 2021) were included (mean age, 64.8 ± 11.6 years; 95.5% male; 70.5% with ischaemic heart disease; a mean ejection fraction of 32.3 ± 7.8%). The characteristics of CMR channels were analysed, and correlations with DZs detected during isochronal late activation mapping in both baseline maps and remaps were determined. Overall, 109 automatically detected CMR channels were analysed (2.48 ± 1.15 per patient; length, 57.91 ± 63.07 mm; conducting channel mass, 2.06 ± 2.67 g; protectedness, 21.44 ± 25.39 mm). Overall, 76.1% of CMR channels were associated with a DZ. A univariate analysis showed that channels associated with DZs were longer [67.81 ± 68.45 vs. 26.31 ± 21.25 mm, odds ratio (OR) 1.03, P = 0.010], with a higher border zone (BZ) mass (2.41 ± 2.91 vs. 0.87 ± 0.86 g, OR 2.46, P = 0.011) and greater protectedness (24.97 ± 27.72 vs. 10.19 ± 9.52 mm, OR 1.08, P = 0.021). Non-invasive detection of targets for VT ablation is possible with CMR. Deceleration zones found during electroanatomical mapping accurately correlate with CMR channels, especially those with increased length, BZ mass, and protectedness.

Case report: Para Hisian Atrial Tachycardia

Case report: Para Hisian Atrial Tachycardia

Outcomes of Focal Pulsed Field Ablation for Paroxysmal Supraventricular Tachycardia

BackgroundPulsed field ablation (PFA) is primarily used for treatment of atrial fibrillation as it provides better safety and efficacy. However, there are limited data available on the use of PFA for paroxysmal supraventricular tachycardia (PSVT). The study sought to describe the outcomes of PSVT ablation with a novel focal contact force (CF)-sensing PFA. MethodsIn this first-in-human pilot study, a focal CF-sensing PFA catheter was used for mapping and ablation navigated with an electroanatomic mapping system (EAMS). Pulsed field energy was delivered as biphasic/bipolar electrical pulse trains with 2000 V/delivery. CF was controlled from 2 g to 10 g during PFA. ResultsProcedural acute success was achieved without general anaesthesia or conscious sedation in all 10 patients, including 7 patients diagnosed with typical atrioventricular nodal re-entrant tachycardias and 3 patients with orthodromic reciprocating tachycardias. Successful target ablation time was 2.0 ± 0.5 seconds per patient, and the acute procedural success at the first single site was achieved in 5 patients. The mean skin-to-skin procedure time was 79.4 ± 15 minutes, PFA catheter dwell time was 50.1 ± 14 minutes, and fluoroscopy time was 6.2 ± 7 minutes. Maintenance of sinus rhythm was observed in all patients within 6-month follow-up. No serious adverse events occurred in any subjects during PFA or during the 6-month follow-up. ConclusionsA focal CF-sensing PFA catheter could effectively, rapidly, and safely ablate PSVT in conscious patients. Clinical Trial RegistrationNCT05770921

Cavotricuspid Isthmus-Dependent Atrial Flutter. Beyond Simple Linear Ablation.

The demonstration of a peritricuspid circular movement with a zone of slow conduction in the cavotricuspid isthmus, together with the high efficacy of linear ablation and widely accepted acute endpoints, has established typical flutter as a disease with a well-defined physiopathology and treatment. However, certain aspects regarding its deeper physiopathology, ablation targets, and methods for verifying the results remain to be clarified. While current research efforts have primarily been focused on the advancement of effective ablation techniques, it is crucial to continue exploring the intricate electrophysiological, ultrastructural, and pharmacological pathways that underlie the development of atrial flutter. This ongoing investigation is essential for the development of targeted preventive strategies that can act upon the specific mechanisms responsible for the initiation and maintenance of this arrhythmia. In this work, we will discuss less ascertained aspects alongside the most widely recognized general data, as well as the most recent or less commonly used contributions regarding the electrophysiological evaluation and ablation of typical atrial flutter. Regarding electrophysiological characteristics, one of the most intriguing findings is the presence of low voltage zones in some of these patients together with the presence of a functional, unidirectional line of block between the two vena cava. It is theorized that episodes of paroxysmal atrial fibrillation can trigger this line of block, which may then allow the onset of stable atrial flutter. Without this, the patient will either remain in atrial fibrillation or return to sinus rhythm. Another of the most important pending tasks is identifying patients at risk of developing post-ablation atrial fibrillation. Discriminating between individuals who will experience a complete arrhythmia cure and those who will develop atrial fibrillation after flutter ablation, remains essential given the important prognostic and therapeutic implications. From the initial X-ray guided linear cavotricuspid ablation, several alternatives have arisen in the last decade: electrophysiological criteria-directed point applications based on entrainment mapping, applications directed by maximum voltage criteria or by wavefront speed and maximum voltage criteria (omnipolar mapping). Electro-anatomical navigation systems offer substantial support in all three strategies. Finally, the electrophysiological techniques to confirm the success of the procedure are reviewed.

Left atrial posterior wall isolation using pulsed-field ablation: procedural characteristics, safety, and mid-term outcomes

BackgroundNon-pulmonary vein (PV) ablation targets such as posterior wall isolation (PWI) have been tested in patients with persistent atrial fibrillation (AF). Pulsed-field ablation (PFA) offers a novel ablation technology possibly able to overcome the obstacles of incomplete PWI and concerns of damage to adjacent structures compared to thermal energy sources. Our aim was to assess procedural characteristics, safety, and mid-term outcomes of patients undergoing PWI using PFA in a clinical setting.MethodsPatients undergoing PFA-PVI with PWI were included. First-pass isolation was controlled using a multipolar mapping catheter.ResultsOne hundred consecutive patients were included (median age 69 [IQR 63–75] years, 33 females (33%), left atrial size 43 [IQR 39–47] mm, paroxysmal AF 24%). Median procedure time was 66 (IQR 59–77) min, and fluoroscopy time was 11 (8–14) min. PWI using PFA was achieved in 100% of patients with a median of 19 applications (IQR 14–26). There were no major complications. Overall, in 15 patients (15%), recurrent AF/AT was noted during a median follow-up of 144 (94–279) days.ConclusionsPWI using PFA appears safe and results in high acute isolation rates and high arrhythmia survival during mid-term follow-up. Further randomized trials are essential and warranted.Graphical abstract

CO2 activation by copper oxide clusters: size, composition, and charge state dependence.

The interaction of CO2 with copper oxide clusters of different size, composition, and charge is investigated via infrared multiple-photon dissociation (IR-MPD) spectroscopy and density functional theory (DFT) calculations. Laser ablation of a copper target in the presence of an O2/He mixture leads to the preferred formation of oxygen-rich copper oxide cluster cations, CuxOy+ (y > x; x ≤ 8), while the anionic cluster distribution is dominated by stoichiometric (x = y) and oxygen-deficient (y < x; x ≤ 8) species. Subsequent reaction of the clusters with CO2 in a flow tube reactor results in the preferred formation of near-stoichiometric CuxOy(CO2)+/- complexes. IR-MPD spectroscopy of the formed complexes reveals the non-activated binding of CO2 to all cations while CO2 is activated by all anions. The great resemblance of spectra for all sizes investigated demonstrates that CO2 activation is largely independent of cluster size and Cu/O ratio but mainly determined by the cluster charge state. Comparison of the IR-MPD spectra with DFT calculations of the model systems Cu2O4(CO2)- and Cu3O4(CO2)- shows that CO2 activation exclusively results in the formation of a CO3 unit. Subsequent CO2 dissociation to CO appears to be unfavorable due to the instability of CO on the copper oxide clusters indicating that potential hydrogenation reactions will most likely proceed via formate or bicarbonate intermediates.

Irradiation modes and phase explosion during ablation of steel targets with a scanning beam of pulsed radiation of a nanosecond duration Yb:YAG laser

Irradiation modes and phase explosion during ablation of steel targets with a scanning beam of pulsed radiation of a nanosecond duration Yb:YAG laser

Best practices in robotic magnetic navigation-guided catheter ablation of cardiac arrhythmias, a position paper of the Society for Cardiac Robotic Navigation.

Robotic magnetic navigation (RMN)-guided catheter ablation (CA) technology has been used for the treatment of cardiac arrhythmias for almost 20 years. Various studies reported that RMN allows for high catheter stability, improved lesion formation and a superior safety profile. So far, no guidelines or recommendations on RMN-guided CA have been published. The aim of this consensus paper was to summarize knowledge and provide recommendations on management of arrhythmias using RMN-guided CA as treatment of atrial fibrillation (AF) and ventricular arrhythmias (VA). An expert writing group, performed a detailed review of available literature, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Recommendations on RMN-guided CA are presented in a guideline format with three levels of recommendations to serve as a reference for best practices in RMN procedures. Each recommendation is accompanied by supportive text and references. The various sections cover the practical spectrum from system and patient set-up, EP laboratory staffing, combination of RMN with fluoroscopy and mapping systems, use of automation features and ablation settings and targets, for different cardiac arrhythmias. This manuscript, presenting the combined experience of expert robotic users and knowledge from the available literature, offers a unique resource for providers interested in the use of RMN in the treatment of cardiac arrhythmias.

Cardioneuroablation: the known and the unknown.

Cardioneuroablation (CNA) is a novel interventional procedure for the treatment of recurrent vasovagal syncope (VVS) and advanced atrioventricular block secondary to hyperactivation of vagal tone in young patients. By damaging the cardiac parasympathetic ganglia, CNA seems to be able to mitigate and/or abolish the excessive vagal activity and improve patients' outcome. This review is intended to give a detailed and comprehensive overview of the current evidences regarding (1) the clinical applications of CNA (2) the identification of ablation targets and procedural endpoints (3) the medium-long term effect of the procedure and its future perspectives. However, clinical data are still limited, and expert consensus or recommendations in the guidelines regarding this technique are still lacking.

Posterior wall ablation by pulsed-field ablation: procedural safety, efficacy, and findings on redo procedures.

The left atrial posterior wall is a potential ablation target in patients with recurrent atrial fibrillation despite durable pulmonary vein isolation or in patients with roof-dependent atrial tachycardia (AT). Pulsed-field ablation (PFA) offers efficient and safe posterior wall ablation (PWA), but available data are scarce. Consecutive patients undergoing PWA using PFA were included. Posterior wall ablation was performed using a pentaspline PFA catheter and verified by 3D-electroanatomical mapping. Follow-up was performed using 7-day Holter ECGs 3, 6, and 12 months after ablation. Recurrence of any atrial arrhythmia lasting more than 30 s was defined as failure. Lesion durability was assessed during redo procedures. Posterior wall ablation was performed in 215 patients (70% males, median age 70 [IQR 61-75] years, 67% redo procedures) and was successful in all patients (100%) by applying a median of 36 (IQR 32-44) PFA lesions. Severe adverse events were cardiac tamponade and vascular access complication in one patient each (0.9%). Median follow-up was 7.3 (IQR 5.0-11.8) months. One-year arrhythmia-free outcome in Kaplan-Meier analysis was 53%. A redo procedure was performed in 26 patients (12%) after a median of 6.9 (IQR 2.4-11) months and showed durable PWA in 22 patients (85%) with only minor lesion regression. Among four patients with posterior wall reconnection, three (75%) presented with roof-dependent AT. Posterior wall ablation with this pentaspline PFA catheter can be safely and efficiently performed with a high durability observed during redo procedures. The added value of durable PWA for the treatment of atrial fibrillation remains to be evaluated.

Impact of stainless steel nano-alloys on biogas production rate: safe catalysts

The feasibility of using nontoxic stainless steel colloidal solutions, synthesized by laser ablation in distilled water, for the production of biogas is examined in this paper. Given that their biodigesters are treated concurrently while taking into account the same experimental and environmental circumstances, certain results are compared with earlier work on NiFe2O4. As a result, the cumulative gas volume after the 50-days incubation period increased to 172 and 207% for NiFe2O4 and stainless steel nano-alloys, respectively. Additionally, the biogas flame and the information at hand are used to interpret the biological effect. The free Cr stainless steel colloidal solution yields an unexpected biogas volume of 207% of control, according to a recent discovery. However, the inhibition of Cr-based stainless steel digesters is attributed to the heat shock mechanism–based NIR resonance fluorescence property.Novelty statementEnhancement of biogas production rate from cow dung by 207%, in comparison to control, using nontoxic stainless steel nano-alloys free of Cr element synthesized by laser ablation of commercial targets in water. However, nano-alloys based on Cr element exhibit an inhibition effect due to a heat shock mechanism. Accordingly, stainless steel nano-alloys synthesized by laser ablation in water are eco-friendly and safe catalysts for applicants and users.Graphical abstract

Mapping of Purkinje-related ventricular arrhythmias by a multispline catheter with small and close-paired electrodes: Comparison with conventional catheters.

Precise mapping of the Purkinje fiber network is essential in catheter ablation of Purkinje-related ventricular arrhythmias (PrVAs). We sought to evaluate the mapping ability of a multi-spline duodecapolar catheter (PentaRay) for PrVAs. Mappings of Purkinje fibers by PentaRay catheters were compared with those by conventional mapping catheters in consecutive patients undergoing catheter ablation of PrVAs from 2015 to 2022. Sixteen PrVAs (7 premature ventricular contractions or non-reentrant fascicular tachycardias [PVCs/NRFTs] and 9 fascicular ventricular tachycardias [FVTs]) were retrospectively studied. In PVCs/NRFTs, earliest preceding Purkinje potentials (PPs) could be recorded by the PentaRay catheters but not by the mapping and ablation catheters in 5 cases. At the earliest PP sites, the precedence from the QRS onset was greater, and the amplitude of the preceding potentials was higher in the PentaRay catheter compared with those in the mapping and ablation catheter (-62.0±42.8vs. -29.4±34.2ms, P=0.02; 0.45±0.43vs. 0.09±0.08mV, P=0.02). In FVTs, late diastolic potentials (P1) were recorded by the PentaRay catheters but not by the mapping and ablation catheters or the linear duodecapolar catheter in 2 cases. The amplitude of P1 was higher in the PentaRay catheter compared with that in the linear duodecapolar catheter and the mapping and ablation catheters (0.72±0.49vs. 0.17±0.18vs. 0.27±0.21mV, P=0.0006, P=0.002). The localized critical PPs, defined as the earliest preceding potentials in PVCs/NRFTs and P1 in FVTs, could be recorded in all the patients by the PentaRay catheter. The mapping ability of critical PPs of PrVAs was better with the PentaRay catheter than with the conventional mapping catheters (16/16vs. 9/16, P=0.004 by McNemar exact test). The PentaRay catheter has clinical advantages in mapping of the Purkinje fiber network to reveal critical PPs as ablation targets of PrVAs.

High-intensity focused ultrasound ablation combined with systemic therapy for unresectable colorectal cancer liver metastasis: A propensity score-matched analysis.

Unresectable colorectal cancer liver metastasis (CRLM) remains a challenging obstacle that often prevents curative treatment. In this study, we retrospectively analyzed the efficacy and safety of high-intensity focused ultrasound (HIFU) as a local adjuvant therapy for systemic chemotherapy for patients with unresectable CRLM. HIFU is a noninvasive method previously demonstrated as efficacious for various solid malignancies. Propensity score matching was used for the combination therapy group (HIFU group, n = 59) and the observation group receiving systemic therapy only (No-HIFU group, n = 59). In addition, the survival benefit, adverse effects, and factors affecting prognosis following HIFU were evaluated. The disease control rate was 77.9% and 62.7%, and the objective remission rate was 18.9% and 6.8% in the HIFU and non-HIFU groups, respectively. The survival analysis showed that median progression-free survival (mPFS) was 12.0 months and 11.0 months for the HIFU and non-HIFU groups, respectively (p = 0.002). The univariate and multivariate analysis showed that pre-treatment colorectal cancer liver metastasis lesion size was significantly associated with mPFS. In addition, patients that received a combination treatment for CRLM lesions <5.0 cm had a longer mPFS when compared to those receiving systemic therapy alone (13.0 months vs. 11.0 months, p = 0.001). In the HIFU group, patients with lesions <5.0 cm had a longer mPFS than patients with lesions ≥5.0 cm (13.0 months vs. 10.0 months, p = 0.04) (Figure3B,C). Most treatment-related adverse events observed in both groups were grade 1-2. Only four cases (6.8%) of grade 1-2 skin burns were observed in patients in the HIFU group; no other statistically significant adverse events were observed. Our study showed that HIFU ablation targeting unresectable CRLM alongside systemic therapy safely and significantly improved local control rates and prolonged mPFS, especially for lesions smaller than 5.0 cm.

Cardioneuroablation for successful treatment of symptomatic bradycardia in a 12-year-old child after a 6-month follow-up

BackgroundCardioneuroablation (CNA) is recognized as a promising therapeutic option for adults with severe symptomatic bradycardia caused by excessive vagal tone. However, no pediatric cases have been reported to date. Therefore, the aim of this study is to evaluate the feasibility and efficacy of CNA in children.MethodsA 12-year-old male patient was hospitalized with symptoms of fatigue, palpitations, and syncope for more than 2 months, and was definitively diagnosed with functional sinoatrial node dysfunction by using a 12-lead electrocardiogram, 24-h Holter monitoring, loading dose of atropine test (0.04 mg/kg), and treadmill exercise test. Simultaneously, whole-exome sequencing was performed on the child and his core family members. After completing the preoperative examination and signing the informed consent form, the child underwent CNA therapy.ResultsFirst, the electroanatomic structures of both atria were mapped out by using the Carto 3 system, according to the protocol of purely anatomy-guided and local fractionated intracardiac electrogram–guided CNA methods. Then, the local fractionated intracardiac electrograms of each cardiac ganglionated plexus (GP), including the GP between the aortic root and the medial wall of the superior vena cava, the GP between the posterior wall of the coronary sinus ostium and the left atrium, the GP between the anterior antrum of the right superior pulmonary vein and the superior vena cava, the GP in the superolateral area around the root of the left superior pulmonary vein, the GP around the root of the right inferior pulmonary vein, and the GP around the root of the left inferior pulmonary vein, were used as targets for ablation at a power of 30 W with an ablation index of 350–400. At a 6-month follow-up, the child's heart rhythm saw a complete restoration to sinus rhythm and clinical symptoms disappeared.ConclusionThe first application of CNA in a child with symptomatic sinus bradycardia was achieved with better clinical outcomes. CNA can be carried out cautiously in children under suitable indications.

Complex repolarization dynamics in ex vivo human ventricles are independent of the restitution properties.

The mechanisms of transition from regular rhythms to ventricular fibrillation (VF) are poorly understood. The concordant to discordant repolarization alternans pathway is extensively studied; however, despite its theoretical centrality, cannot guide ablation. We hypothesize that complex repolarization dynamics, i.e. oscillations in the repolarization phase of action potentials with periods over two of classic alternans, is a marker of electrically unstable substrate, and ablation of these areas has a stabilizing effect and may reduce the risk of VF. To prove the existence of higher-order periodicities in human hearts. We performed optical mapping of explanted human hearts obtained from recipients of heart transplantation at the time of surgery. Signals recorded from the right ventricle endocardial surface were processed to detect global and local repolarization dynamics during rapid pacing. A statistically significant global 1:4 peak was seen in three of six hearts. Local (pixel-wise) analysis revealed the spatially heterogeneous distribution of Periods 4, 6, and 8, with the regional presence of periods greater than two in all the hearts. There was no significant correlation between the underlying restitution properties and the period of each pixel. We present evidence of complex higher-order periodicities and the co-existence of such regions with stable non-chaotic areas in ex vivo human hearts. We infer that the oscillation of the calcium cycling machinery is the primary mechanism of higher-order dynamics. These higher-order regions may act as niduses of instability and may provide targets for substrate-based ablation of VF.

Revelation after three decades of ablation therapy: two loops instead of a single re-entry loop drive atrial tachycardia

Revelation after three decades of ablation therapy: two loops instead of a single re-entry loop drive atrial tachycardia There is an urgent need to better understand and localise the sources of cardiac arrhythmia in order to improve its treatment. SmartHeart proposes a radical new approach—applying network theory to study cardiac arrhythmia mechanisms. Network theory has myriad applications throughout biology, physics and social sciences. However, it has never been applied to the heart. In this proposal, we will apply network theory to clinical data of cardiac arrhythmia, backed up by computer simulations, to automatically detect the source of the arrhythmia for complex atrial tachycardia, atrial fibrillation and ventricular tachycardia. As we will identify possible ablation targets, the goal of this project is to improve the treatment for the patient.