Nick Linton

Imperial College London | Imperial · Department of Bioengineering

RETRO‐mapping was developed to automate activation mapping of atrial fibrillation (AF). We used the algorithm to study the effect of pulmonary vein isolation (PVI) on the frequency of focal, planar, and colliding wavefronts in persistent AF. An AFocusII catheter was placed on the left atrial endocardium to record 3 s of AF at six sites pre and post...

Aims Left bundle branch pacing (LBBP) can deliver physiological left ventricular activation, but typically at the cost of delayed right ventricular (RV) activation. Right ventricular activation can be advanced through anodal capture, but there is uncertainty regarding the mechanism by which this is achieved, and it is not known whether this produce...

Background: The use of left bundle branch area pacing (LBBAP) for bradycardia pacing and cardiac resynchronization is increasing, but implants are not always successful. We prospectively studied consecutive patients to determine whether septal scar contributes to implant failure. Methods: Patients scheduled for bradycardia pacing or cardiac resy...

Background: Despite effective therapies, the economic burden of heart failure with reduced ejection fraction (HFrEF) is driven by frequent hospitalizations. Treatment optimization and admission avoidance rely on frequent symptom reviews and monitoring of vital signs. Remote monitoring (RM) aims to prevent admissions by facilitating early intervent...

Background: Community-based management by heart failure specialist nurses (HFSNs) is key to improving self-care in heart failure with reduced ejection fraction. Remote monitoring (RM) can aid nurse-led management, but in the literature, user feedback evaluation is skewed in favor of the patient rather than nursing user experience. Furthermore, the...

Background: Getting the most value from expert clinicians' limited labelling time is a major challenge for artificial intelligence (AI) development in clinical imaging. We present a novel method for ground-truth labelling of cardiac magnetic resonance imaging (CMR) image data by leveraging multiple clinician experts ranking multiple images on a si...

Background: A quantifiable, automated standard of analysing heart rhythm has long eluded cardiologists due, in part, to the limitations in technology and the ability to analyse large electrogram datasets. In this proof-of-concept study, we propose new measures to quantify plane activity in atrial fibrillation (AF) using our RETRO-Mapping software....

Aims: Left bundle branch area pacing (LBBAP) is a promising method for delivering cardiac resynchronization therapy (CRT), but its relative physiological effectiveness compared with His bundle pacing (HBP) is unknown. We conducted a within-patient comparison of HBP, LBBAP, and biventricular pacing (BVP). Methods and results: Patients referred fo...

BACKGROUND Despite effective therapies, the economic burden of heart failure with reduced ejection fraction (HFrEF) is driven by frequent hospitalizations. Treatment optimization and admission avoidance rely on frequent symptom reviews and monitoring of vital signs. Remote monitoring (RM) aims to prevent admissions by facilitating early interventio...

BACKGROUND Community-based management by heart failure specialist nurses (HFSNs) is key to improving self-care in heart failure with reduced ejection fraction. Remote monitoring (RM) can aid nurse-led management, but in the literature, user feedback evaluation is skewed in favor of the patient rather than nursing user experience. Furthermore, the w...

Background: Atrial fibrillation (AF) and ventricular fibrillation (VF) are complex heart rhythm disorders and may be sustained by distinct electrophysiological mechanisms. Disorganised self-perpetuating multiple-wavelets and organised rotational drivers (RDs) localising to specific areas are both possible mechanisms by which fibrillation is sustain...

Background - The mechanisms underlying AF remain controversial. We developed RETRO-Mapping to characterize activation wavefronts by direction and uniformity, accumulating data as an orbital plot and analyzed as frequency histograms. We applied this technique to patients undergoing AF ablation to determine if AF activation is random. Methods - Patie...

The large number of available MRI sequences means patients cannot realistically undergo them all, so the range of sequences to be acquired during a scan are protocolled based on clinical details. Adapting this to unexpected findings identified early on in the scan requires experience and vigilance. We investigated whether deep learning of the image...

Background Electroanatomic mapping systems are used to support electrophysiology research. Data exported from these systems is stored in proprietary formats which are challenging to access and storage-space inefficient. No previous work has made available an open-source platform for parsing and interrogating this data in a standardized format. We t...

Objectives: The authors reviewed 3-dimensional electroanatomic maps of perimitral flutter to identify scar-related isthmuses and determine their effectiveness as ablation sites. Background: Perimitral flutter is usually treated by linear ablation between the left lower pulmonary vein and mitral annulus. Conduction block can be difficult to achie...

Background: Ganglionated plexuses (GP) are implicated in atrial fibrillation (AF). Endocardial high frequency stimulation (HFS) delivered within the local atrial refractory period can trigger ectopy and AF from specific GP sites (ET-GP). The aim of this study was to understand the role of ET-GP ablation in the treatment of AF. Methods and results:...

Background Filtering facepiece (FFP) respirators must provide an adequate faceseal to protect healthcare workers from harmful particles. A qualitative fit-test using bitter-tasting aerosols the commonest way to determine if an FFP mask is safe enough for clinical use. This taste-test is subjective and can be biased by placebo. We propose a cheap an...

Aims : Rate adaptation of the action potential ensures spatial heterogeneities in conduction across the myocardium are minimized at different heart rates providing a protective mechanism against ventricular fibrillation (VF) and sudden cardiac death (SCD), which can be quantified by the ventricular conduction stability (V-CoS) test previously desc...

Background His-bundle pacing (HBP) has emerged as an alternative to conventional ventricular pacing because of its ability to deliver physiological ventricular activation. Pacing at the His bundle produces different electrocardiographic (ECG) responses: selective His-bundle pacing (S-HBP), non-selective His bundle pacing (NS-HBP), and myocardium-on...

Echocardiography is the commonest medical ultrasound examination, but automated interpretation is challenging and hinges on correct recognition of the 'view' (imaging plane and orientation). Current state-of-the-art methods for identifying the view computationally involve 2-dimensional convolutional neural networks (CNNs), but these merely classify...

Background - The mechanisms sustaining myocardial fibrillation remain disputed, partly due to a lack of mapping tools that can accurately identify the mechanism with low spatial resolution clinical recordings. Granger causality (GC) analysis, an econometric tool for quantifying causal relationships between complex time-series, was developed as a no...

Background: Ripple mapping (RM) is an alternative approach to activation mapping of atrial tachycardia (AT) that avoids electrogram annotation. We tested whether RM is superior to conventional annotation based local activation time (LAT) mapping for AT diagnosis in a randomized and multicenter study. Methods: Patients with AT were randomized to...

Background: Conventional mapping techniques during atrial fibrillation (AF) are difficult to apply because of cycle length irregularity. Mapping studies are usually restricted to short durations of AF in limited regions because of the laborious manual annotation of local activation time (LAT). The purpose of this study was to test an automated alg...

Background: Bipolar electrogram voltage during sinus rhythm (VSR) has been used as a surrogate for atrial fibrosis in guiding catheter ablation of persistent atrial fibrillation (AF), but the fixed rate and wavefront characteristics present during sinus rhythm may not accurately reflect underlying functional vulnerabilities responsible for AF main...

Objectives: This study sought to test specialized processing of laser Doppler signals for discriminating ventricular fibrillation (VF) from common causes of inappropriate therapies. Background: Inappropriate implantable cardioverter-defibrillator (ICD) therapies remain a clinically important problem associated with morbidity and mortality. Tissu...

Introduction The ganglionated plexuses (GPs) of the intrinsic cardiac autonomic system are implicated in arrhythmogenesis. GP localization by stimulation of the epicardial fat pads to produce atrioventricular dissociating (AVD) effects is well described. We determined the anatomical distribution of the left atrial GPs that influence AV dissociation...

Understanding the mechanisms responsible for driving AF is key to improving the procedural success for AF ablation. In this review, we look at some of the proposed drivers of AF, the disagreement between experts and the challenges confronted in attempting to map AF. Defining a ‘driver’ is also controversial, but for the purposes of this review we w...

Background: Post ablation reentrant ATs depend upon conducting isthmuses bordered by scar. Bipolar voltage maps highlight scar as sites of low voltage, but the voltage amplitude of an electrogram depends upon the myocardial activation sequence. Furthermore, a voltage threshold that defines atrial scar is unknown. We used Ripple Mapping (RM) to tes...

Background: Ripple Mapping (RM) displays electrograms as moving bars over a 3D surface displaying bipolar voltage, and has shown in a single-center series to be effective for atrial tachycardia (AT) mapping without annotation of local activation time or window-of-interest assignment. We tested the reproducibility of these findings in operators nai...

Introduction: Bipolar voltage is used during electroanatomic mapping to define abnormal myocardium, but the effect of activation rate on bipolar voltage is not known. We hypothesized that bipolar voltage may change in response to activation rate. By examining corresponding unipole signals we sought to determine the mechanisms of such changes. Met...

Background: The activation pattern of localized reentry (LR) in atrial tachycardia remains incompletely understood. We used the ultra-high density Rhythmia mapping system to study activation patterns in LR. Methods and results: LR was suggested by small rotatory activations (carousels) containing the full spectrum of the color-coded map. Twenty-...

Objectives This study sought to characterize direction-dependent and coupling interval–dependent changes in left atrial conduction and electrogram morphology in uniformly classified patients with paroxysmal atrial fibrillation (AF) and normal bipolar voltage mapping. Background Although AF classifications are based on arrhythmia duration, the clin...

Here is an example of using Dot Mapping to overlay two datasets - in this example epicardial bipolar voltage is shown above endocardial bipolar voltage. The Dot Map allows the user to 'see through' the dataset to the information below.

Aims Complex ablation procedures are supported by accurate representation of an increasing variety of electrophysiological and imaging data within electroanatomic mapping systems (EMS). This study aims to develop a novel method for representing multiple complementary datasets on a single cardiac chamber model. Validation of the system and its appli...

Electrical Remodelling Does not Reproducibly Mirror Structural Change on Atrial MRI

Purpose of the Study Although atrial fibrillation (AF) is classified by arrhythmia duration, the presentation, clinical course and response to treatment vary widely within paroxysmal AF (PAF) patients. We hypothesized that variable electrical remodeling exists between PAF patients, resulting in intra-atrial conduction delay which could be identifie...

Background: Post-infarct ventricular tachycardia is associated with channels of surviving myocardium within scar characterized by fractionated and low-amplitude signals usually occurring late during sinus rhythm. Conventional automated algorithms for 3-dimensional electro-anatomic mapping cannot differentiate the delayed local signal of conduction...

Purpose of the Study: Left atrial (LA) late gadolinium enhancement (LGE) CMR has been proposed to guide ablation therapy and predict procedure outcome. AF electrical and structural remodeling are known to occur to varying extents in patients with AF. The extent to which pre-procedural LGE CMR reflects LA electrophysiological remodeling is unknown....

Purpose of the Study: Although atrial fibrillation (AF) is classified by arrhythmia duration, the presentation, clinical course and response to treatment vary widely within paroxysmal AF (PAF) patients. We hypothesized that variable electrical remodeling exists between PAF patients, resulting in intra-atrial conduction delay which could be identifi...

Patient-specific Dynamic Electrophysiological Characterization Reveals Heterogeneity Between Paroxysmal AF Patients

Electrical Remodeling does not Reproducibly Mirror Structural Change on Atrial MRI

Background— Post ablation atrial tachycardias are characterized by low-voltage signals that challenge current mapping methods. Ripple mapping (RM) displays every electrogram deflection as a bar moving from the cardiac surface, resulting in the impression of propagating wavefronts when a series of bars move consecutively. RM displays fractionated si...

Objectives The purpose of this study was to investigate whether heart failure patients with narrow QRS duration (or right bundle branch block) but with long PR interval gain acute hemodynamic benefit from atrioventricular (AV) optimization. We tested this with biventricular pacing and (to deliver pure AV shortening) direct His bundle pacing. Backg...

Ripple Mapping (RM) is designed to overcome the limitations of existing isochronal 3D mapping systems by representing the intracardiac electrogram as a dynamic bar on a surface bipolar voltage map that changes in height according to the electrogram voltage-time relationship, relative to a fiduciary point. We tested the hypothesis that standard appr...

Robotically guided radiofrequency (RF) ablation offers greater catheter stability that may improve lesion depth. We performed a non-randomised comparison of patients undergoing ventricular tachycardia (VT) ablation either manually or robotically using the Hansen Sensei system for recurrent implantable defibrillator (ICD) therapy. Patients with infa...

Mitral isthmus (MI) ablation is an effective option in patients undergoing ablation for persistent atrial fibrillation (AF). Achieving bidirectional conduction block across the MI is challenging, and predictors of MI ablation success remain incompletely understood. We sought to determine the impact of anatomical location of the ablation line on the...

-Studies have reported an inverse relationship between LGE CMR signal intensity and LA endocardial voltage following LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between a...

-This study aimed to determine five-year efficacy of catheter ablation for persistent atrial fibrillation (PsAF) using AF termination as a procedural endpoint. -150 patients (57±10 years) underwent PsAF ablation using a stepwise ablation approach (pulmonary vein isolation, electrogram-guided and linear ablation) with the desired procedural endpoint...

-Ripple Mapping (RM) displays each electrogram at its 3D coordinate as a bar changing in length according to its voltage-time relationship with a fiduciary reference. We applied RM to left ventricular (LV) ischemic scar for evidence of slow conducting channels that may act as ventricular tachycardia (VT) substrate. -CARTO-3© maps in patient undergo...

Introduction: Robotically-guided ablation offers theoretical advantages with greater catheter stability that can improve lesion depth. We performed a non-randomised comparison of patients undergoing ventricular tachycardia (VT) ablation either manually or using the Hansen robotic system. Methods: Consecutive patients with infarct-related scar under...

Introduction: Atrial structural remodelling contributes to the progression of AF and complex fractionated atrial electrograms (CFAE) may represent sites of structural remodelling. However, CFAE is a dynamic and rate-related phenomenon. We sought to compare rate-dependence of CFAE under paced conditions in PAF patients and a control group undergoing...

Introduction: Adult congenital heart disease (ACHD) patients have a high lifetime prevalence of reentrant atrial arrhythmia, secondary to both the anatomic lesion and surgical repair. Catheter ablation is an effective treatment for atrial tachycardia (AT), however current electroanatomical mapping (EAM) systems permit the display of only a single d...

Introduction: Ventricular scar is characterised by fractionated electrograms (egm) and not well displayed by current 3D mapping systems. We hypothesised that displaying intracardiac egms on 3D geometry as dynamic bars changing height according to the voltage-time relationship relative to a fiduciary egm, would enable visualisation slow conduction c...

A Novel Technique for Dual Electrophysiological Dataset Representation: Dot Mapping Facilitates Recognition of Complex Intra-atrial Re-entrant Tachycardia Substrate in Repaired Adult Congenital Heart Disease

Optimised Atrial Local Activation Time Sampling Density and Technique

-The early repolarization (ER) pattern on the electrocardiogram (ECG) is associated with an increased risk of idiopathic ventricular fibrillation (VF). Hypothermia is known to result in similar electrocardiographic changes. In this retrospective cohort study we examine the impact of therapeutic hypothermia on ER in survivors of cardiac arrest attri...

To provide a comprehensive histopathological validation of cardiac magnetic resonance (CMR) and endocardial voltage mapping of acute and chronic atrial ablation injury. 16 pigs underwent pre-ablation T2-weighted (T2W) and late gadolinium enhancement (LGE) CMR and high-density voltage mapping of the right atrium (RA) and both were repeated after int...

Late Gadolinium Enhancement Cardiac Magnetic Resonance Prediction of Atrial Endocardial Voltage Following Left Atrial Catheter Ablation

Can Late Gadolinium Enhancement Cardiac Magnetic Resonance Reliably Predict Gaps in Atrial Ablation Lesions?

Optimal Local Activation Time Sampling Density For Atrial Tachyarrhythmias is Independent of Tachycardia Mechanism

Spatiotemporal characterisation of Dominant Frequency Organisation using High Density Noncontact Mapping of Persistent Atrial Fibrillation Joao Salinet1, MSc, Jiun Tuan2, MD, Peter Stafford2,3, MD, FRCP, Fernando S. Schlindwein1,3, PhD and G. André Ng2,3, PhD, FRCP. Introduction: Preclinical studies suggest that rotors may be responsible for th...