SuperMap algorithm: an efficient, safe and accurate modality for mapping and eliminating challenging cardiac arrhythmias.

Even with the development of advanced catheter-based mapping systems, there remain several challenges in the electrophysiological evaluation and elimination of atrial arrhythmias. For instance, atrial tachycardias with irregular rates cannot be reliably mapped by systems that require stability in order to sequentially gather data points to be organized thereafter. Separately, these arrhythmias often arise following initial ablation for atrial fibrillation, posing logistic challenges. Here, we present the available literature summarizing the use of a non-contact mapping catheter, the AcQMap catheter, in conjunction with SuperMap, an algorithm that compiles a large number of non-contact data points from multiple catheter positions within the atria. These studies demonstrate the efficiency, safety and accuracy of this technology.

Irregular heart rhythms (arrhythmias) are often treatable with medications, but sometimes require expert evaluation in a cardiac electrophysiology laboratory. They are often studied and treated using thin, flexible catheters which enter the body through blood vessels in the leg and reach the internal walls of the heart. Time, expertise and specialized equipment are necessary to identify characteristics specific to each patient's arrhythmia. For each arrhythmia, a unique electrical blueprint is created before trying to eliminate it. The fleeting nature of certain arrhythmias can make it difficult to generate these blueprints, and many take a lot of time to accurately identify, leading to procedural challenges. Here we evaluate studies discussing the use of a new catheter (AcQMap) and its accompanying strategy for identifying arrhythmias. Unlike traditional catheters that require direct contact with the internal walls of the heart, the AcQMap catheter floats within these blood-filled chambers and does not touch the walls when obtaining data points. Instead, using ultrasound waves and electrical signals, it can generate data points to create blueprints. This technology also uses a new algorithm that enables the catheter to move freely within the heart, obtaining numerous data points and grouping them together to create maps efficiently and safely, even for fleeting or challenging arrhythmias.

Spatially Conserved Spiral Wave Activity During Human Atrial Fibrillation.

BACKGROUND: Atrial fibrillation is the most common cardiac arrhythmia in the world and increases the risk for stroke and morbidity. During atrial fibrillation, the electric activation fronts are no longer coherently propagating through the tissue and, instead, show rotational activity, consistent with spiral wave activation, focal activity, collision, or partial versions of these spatial patterns. An unexplained phenomenon is that although simulations of cardiac models abundantly demonstrate spiral waves, clinical recordings often show only intermittent spiral wave activity. METHODS: In silico data were generated using simulations in which spiral waves were continuously created and annihilated and in simulations in which a spiral wave was intermittently trapped at a heterogeneity. Clinically, spatio-temporal activation maps were constructed using 60 s recordings from a 64 electrode catheter within the atrium of N=34 patients (n=24 persistent atrial fibrillation). The location of clockwise and counterclockwise rotating spiral waves was quantified and all intervals during which these spiral waves were present were determined. For each interval, the angle of rotation as a function of time was computed and used to determine whether the spiral wave returned in step or changed phase at the start of each interval. RESULTS: In both simulations, spiral waves did not come back in phase and were out of step." In contrast, spiral waves returned in step in the majority (68%; P=0.05) of patients. Thus, the intermittently observed rotational activity in these patients is due to a temporally and spatially conserved spiral wave and not due to ones that are newly created at the onset of each interval. CONCLUSIONS: Intermittency of spiral wave activity represents conserved spiral wave activity of long, but interrupted duration or transient spiral activity, in the majority of patients. This finding could have important ramifications for identifying clinically important forms of atrial fibrillation and in guiding treatment.

Excess Mortality Among US Physicians During the COVID-19 Pandemic.

This cross-sectional study examines the death rates among active and nonactive physicians aged 45 to 84 years.

Stochastic termination of spiral wave dynamics in cardiac tissue.

Rotating spiral waves are self-organized features in spatially extended excitable media and may play an important role in cardiac arrhythmias including atrial fibrillation (AF). In homogeneous media, spiral wave dynamics are perpetuated through spiral wave breakup, leading to the continuous birth and death of spiral waves, but have a finite probability of termination. In non-homogeneous media, however, heterogeneities can act as anchoring sources that result in sustained spiral wave activity. It is thus unclear how and if AF may terminate following the removal of putative spiral wave sources in patients. Here, we address this question using computer simulations in which a stable spiral wave is trapped by an heterogeneity and is surrounded by spiral wave breakup. We show that, following ablation of spatial heterogeneity to render that region of the medium unexcitable, termination of spiral wave dynamics is stochastic and Poisson-distributed. Furthermore, we show that the dynamics can be accurately described by a master equation using birth and death rates. To validate these predictions in vivo, we mapped spiral wave activity in patients with AF and targeted the locations of spiral wave sources using radiofrequency ablation. Targeted ablation was indeed able to terminate AF, but only after a variable delay of up to several minutes. Furthermore, and consistent with numerical simulations, termination was not accompanied by gradual temporal or spatial organization. Our results suggest that spiral wave sources and tissue heterogeneities play a critical role in the maintenance of AF and that the removal of sources results in spiral wave dynamics with a finite termination time, which could have important clinical implications.

Future Directions for Mapping Atrial Fibrillation.

Mapping for AF focuses on the identification of regions of interest that may guide management and - in particular - ablation therapy. Mapping may point to specific mechanisms associated with localised scar or fibrosis, or electrical features, such as localised repetitive, rotational or focal activation. In patients in whom AF is caused by disorganised waves with no spatial predilection, as proposed in the multiwavelet theory for AF, mapping would be of less benefit. The role of AF mapping is controversial at the current time in view of the debate over the underlying mechanisms. However, recent clinical expansions of mapping technologies confirm the importance of understanding the state of the art, including limitations of current approaches and potential areas of future development.

Atrial fibrillation mechanisms before and after pulmonary vein isolation characterized by noncontact charge density mapping.

BACKGROUND: The interaction of the pulmonary vein (PV) and putative nonpulmonary triggers of atrial fibrillation (AF) remains unclear and has yet to translate into patient-tailored ablation strategies. OBJECTIVE: The purpose of this study was to use noncontact mapping to detail the global conduction patterns in paroxysmal and persistent AF and how they are modified during PV ablation. METHODS: Forty patients during AF ablation underwent mapping using a noncontact catheter (AcQMap, Acutus Medical, Inc., Carlsbad, CA) before and after PV isolation (PVI). Propagation history maps were analyzed postprocedure for each patient to categorize conduction patterns into focal, organized reentrant, and disorganized patterns (F-Patterns, O-Patterns, and D-Patterns, respectively). RESULTS: Activation patterns identified by using a noncontact mapping system can be subclassified from 3 main patterns into subtypes (macroreentrant and localized reentrant [MR and LR] subtypes and disorganized 1 and disorganized 2 [D1 and D2] subtypes). Persistent AF demonstrated more D-Patterns and less O-Patterns and F-Patterns than did paroxysmal AF. In addition, patients with PAF inducible after PVI demonstrated a higher region number and higher prevalence of MR subtypes than did those noninducible. PVs remained the critical region and included almost one-third of all patterns across any AF types. PVI was effective to eliminate PV-related functional phenotypes and affected recurrence with other patterns. CONCLUSION: Activation patterns identified using AcQMap can be classified into 3 main patterns (F-Patterns, O-Patterns, and D-Patterns) as well as subtypes (MR and LR subtypes and D1 and D2 subtypes). PerAF was different from PAF in demonstrating a higher region number and higher prevalence of D-Patterns but a lower region number and lower prevalence of O-Patterns and F-Patterns.

Novel aggregated multiposition noncontact mapping of atrial tachycardia in humans: From computational modeling to clinical validation.

BACKGROUND: A novel aggregated multiposition noncontact mapping (AMP-NCM) algorithm is proposed to diagnose cardiac arrhythmias. OBJECTIVE: The purpose of this study was to computationally determine an accuracy threshold and to compare the accuracy and clinical utility of AMP-NCM to gold standard contact mapping. METHODS: In a cellular automata model, the number of catheter positions and chamber coverage were varied to establish accuracy requirements for clinically relevant AMP-NCM. This guided the clinical study protocol. In a prospective cohort of patients with atrial tachycardia (AT), noncontact mapping (NCM) recordings from a single position (SP) and multiple positions were compared to contact mapping with a high-density multipolar catheter using morphology and timing differences of reconstructed signals. Identification of AT mechanisms and ablation targets using both AMP-NCM and contact mapping were randomly evaluated by 5 blinded reviewers. RESULTS: AMP-NCM accuracy was asymptotic at 60 catheter positions in computational modeling. Twenty patients (age 65 ± 12 years; 19 male) with 26 ATs (5 focal, 21 reentrant) were studied. Morphologic correlation of signals derived from AMP-NCM was significantly better than those from SP-NCM compared to contact signals (median 0.93 vs 0.76; P <.001). AMP-NCM generated maps more rapidly than contact mapping (3 ± 1 minutes vs 13 ± 6 minutes; P <.001) and correctly diagnosed AT mechanisms in 25 of 26 maps (96%). Overall, 80% of arrhythmia mechanisms were correctly identified using AMP-NCM by blinded reviewers. CONCLUSION: Once 60 catheter positions were achieved, AMP-NCM successfully diagnosed mechanisms of AT and identified treatment sites equal to gold standard contact mapping in 3 minutes of procedural time.

Current perspectives on wearable rhythm recordings for clinical decision-making: the wEHRAbles 2 survey.

Novel wearable devices for heart rhythm analysis using either photoplethysmography (PPG) or electrocardiogram (ECG) are in daily clinical practice. This survey aimed to assess impact of these technologies on physicians' clinical decision-making and to define, how data from these devices should be presented and integrated into clinical practice. The online survey included 22 questions, focusing on the diagnosis of atrial fibrillation (AF) based on wearable rhythm device recordings, suitable indications for wearable rhythm devices, data presentation and processing, reimbursement, and future perspectives. A total of 539 respondents {median age 38 [interquartile range (IQR) 34-46] years, 29% female} from 51 countries world-wide completed the survey. Whilst most respondents would diagnose AF (83%), fewer would initiate oral anticoagulation therapy based on a single-lead ECG tracing. Significantly fewer still (27%) would make the diagnosis based on PPG-based tracing. Wearable ECG technology is acceptable for the majority of respondents for screening, diagnostics, monitoring, and follow-up of arrhythmia patients, while respondents were more reluctant to use PPG technology for these indications. Most respondents (74%) would advocate systematic screening for AF using wearable rhythm devices, starting at patients' median age of 60 (IQR 50-65) years. Thirty-six percent of respondents stated that there is no reimbursement for diagnostics involving wearable rhythm devices in their countries. Most respondents (56.4%) believe that costs of wearable rhythm devices should be shared between patients and insurances. Wearable single- or multiple-lead ECG technology is accepted for multiple indications in current clinical practice and triggers AF diagnosis and treatment. The unmet needs that call for action are reimbursement plans and integration of wearable rhythm device data into patient's files and hospital information systems.

Cecal bascule - An unusual cause of intestinal obstruction: A case report.

INTRODUCTION: Cecal bascule is a rare type of cecal volvulus occurring in the elderly population with a male predominance. It is a condition where the cecum folds upward upon itself. IMPORTANCE: There are only a handful of case reports published about cecal bascule. This is the first case being reported from Pakistan. CASE PRESENTATION: A 68 year old female, known hypertensive and osteoporosis presented in the ER with complaints of vomiting, abdominal distension and absolute constipation. Radiology was non-diagnostic. She was treated with cecectomy and anastomosis. Post operatively she developed ileus for which was managed. She was subsequently discharged at 8th day post op. CLINICAL DISCUSSION: The management of cecal bascule is always surgery with predilection towards cecopexy or cecetomy to prevent recurrence. This manuscript is as per the SCARE case report checklist [1].

Individualized ablation strategy to treat persistent atrial fibrillation: Core-to-boundary approach guided by charge-density mapping.

BACKGROUND: Noncontact charge-density mapping allows rapid real-time global mapping of atrial fibrillation (AF), offering the opportunity for a personalized ablation strategy. OBJECTIVE: The purpose of this study was to compare the 2-year outcome of an individualized strategy consisting of pulmonary vein isolation (PVI) plus core-to-boundary ablation (targeting the conduction pattern core with an extension to the nearest nonconducting boundary) guided by charge-density mapping, with an empirical PVI plus posterior wall electrical isolation (PWI) strategy. METHODS: Forty patients (age 62 ± 12 years; 29 male) with persistent AF (10 ± 5 months) prospectively underwent charge-density mapping-guided PVI, followed by core-to-boundary stepwise ablation until termination of AF or depletion of identified cores. Freedom from AF/atrial tachycardia (AT) at 24 months was compared with a propensity score-matched control group of 80 patients with empirical PVI + PWI guided by conventional contact mapping. RESULTS: Acute AF termination occurred in 8 of 40 patients after charge-density mapping-guided PVI alone and in 21 of the remaining 32 patients after core-to-boundary ablation in the study cohort, compared with 8 of 80 (10%) in the control cohort (P <.001). On average, 2.2 ± 0.6 cores were ablated post-PVI before acute AF termination. At 24 months, freedom from AF/AT after a single procedure was 68% in the study group vs 46% in the control group (P = .043). CONCLUSION: An individualized ablation strategy consisting of PVI plus core-to-boundary ablation guided by noncontact charge-density mapping is a feasible and effective strategy for treating persistent AF, with a favorable 24-month outcome.

Spectral characterization and impact of stepwise ablation protocol including LAA electrical isolation on persistent AF.

OBJECTIVES: To study how left atrial appendage electrical isolation (LAAEI) impacts atrial dominant frequency (DF) in patients with long-standing persistent atrial fibrillation (LSPAF). BACKGROUND: LAAEI is associated with a high probability of freedom from atrial fibrillation (AF) and spectral analysis may identify high-frequency sources. How LAAEI impacts the AF dynamics and the subgroup of LSPAF patients in whom LAAEI would be most beneficial, is unclear. METHODS: Twenty patients with LSPAF were included in the study. Fast Fourier transforms (FFT) were performed on atrial electrograms recorded from 13 sites in the LA and RA. The highest peak frequency was defined as DF. RESULTS: There was no significant difference in DF between atrial sites except for at the superior vena cava which had the lowest DF at baseline. Stepwise ablation consisting of circumferential pulmonary vein isolation and a linear ablation set of mitral isthmus and roof significantly reduced the DF within the coronary sinus (CS) (5.93 ± 0.98 Hz vs. 5.09 ± 0.72 Hz, p < .05) and the LA posterior wall (LApos) (6.26 ± 0.92 Hz vs. 5.43 ± 0.98 Hz, p < .01). LAAEI preferentially further decreased the DF at the LApos (p < .01), but not at the CS. In cases where there was < 13.6% reduction in the DF of the LApos following the stepwise ablation, the addition of LAAEI was associated with an increased restoration of sinus rhythm (55%, p < .05). CONCLUSION: LAAEI in addition to stepwise ablation results in further reduction of the DF in the LApos, which is associated with acute termination of AF and favorable ablation outcome.

Catheter Ablation of Atrial Fibrillation in Patients With Functional Mitral Regurgitation and Left Ventricular Systolic Dysfunction.

Background: The efficacy of catheter ablation for atrial fibrillation (AF) in patients with functional mitral regurgitation (MR) and left ventricular (LV) systolic dysfunction (LVSD) is not known. The aim of the study is to determine the efficacy of catheter ablation for AF in patients with functional MR and LVSD, and to validate its effects on the severity of MR and cardiac reverse remodeling. Methods: We performed a retrospective study of 54 patients with functional MR who underwent AF ablation, including 21 (38.9%) with LVSD and 33 (61.1%) with normal LV systolic function (LVF). The primary outcomes evaluated were freedom from recurrent atrial tachyarrhythmia (ATa), severity of MR, and left atrial (LA) and LV remodeling. Results: During a mean follow-up of 20.7 ± 16.8 months, freedom from recurrent ATa was not significantly different between patients with LVSD and those with normal LVF after the first ablation (P = 0.301) and after multiple ablations (P = 0.728). Multivariable predictors of recurrent ATa were AF duration [hazard ratio (HR) 1.12, 95% confidence interval (CI) 1.01-1.25; P = 0.039), previous stroke (HR 5.28, 95% CI 1.46-19.14; P = 0.011), and estimated glomerular filtration rate (HR 0.97, 95% CI 0.95-0.99; P = 0.012). Compared with baseline, there was a significant reduction in severity of MR (P = 0.007), LA size (P < 0.001) and LV end-systolic dimension (P = 0.008), and improvement in the LV ejection fraction (P = 0.001) after restoring sinus rhythm in patients with LVSD. Conclusion: Catheter ablation is a valid option for the treatment of AF in patients with functional MR and LVSD, even though multiple procedures may be required.

Diverse activation patterns during persistent atrial fibrillation by noncontact charge-density mapping of human atrium.

BACKGROUND: Global simultaneous recording of atrial activation during atrial fibrillation (AF) can elucidate underlying mechanisms contributing to AF maintenance. A better understanding of these mechanisms may allow for an individualized ablation strategy to treat persistent AF. The study aims to characterize left atrial endocardial activation patterns during AF using noncontact charge-density mapping. METHODS: Twenty-five patients with persistent AF were studied. Activation patterns were characterized into three subtypes: (i) focal with centrifugal activation (FCA); (ii) localized rotational activation (LRA); and (iii) localized irregular activation (LIA). Continuous activation patterns were analyzed and distributed in 18 defined regions in the left atrium. RESULTS: A total of 144 AF segments with 1068 activation patterns were analyzed. The most common pattern during AF was LIA (63%) which consists of four disparate features of activation: slow conduction (45%), pivoting (30%), collision (16%), and acceleration (7%). LRA was the second-most common pattern (20%). FCA accounted for 17% of all activations, arising frequently from the pulmonary veins (PVs)/ostia. A majority of patients (24/25; 96%) showed continuous and highly dynamic patterns of activation comprising multiple combinations of FCA, LRA, and LIA, transitioning from one to the other without a discernible order. Preferential conduction areas were typically seen in the mid-anterior (48%) and lower-posterior (40%) walls. CONCLUSION: Atrial fibrillation is characterized by heterogeneous activation patterns identified in PV-ostia and non-PV regions throughout the LA at varying locations between individuals. Clinical implications of individualized ablation strategies guided by charge-density mapping need to be determined.

Machine Learning to Classify Intracardiac Electrical Patterns During Atrial Fibrillation: Machine Learning of Atrial Fibrillation.

BACKGROUND: Advances in ablation for atrial fibrillation (AF) continue to be hindered by ambiguities in mapping, even between experts. We hypothesized that convolutional neural networks (CNN) may enable objective analysis of intracardiac activation in AF, which could be applied clinically if CNN classifications could also be explained. METHODS: We performed panoramic recording of bi-atrial electrical signals in AF. We used the Hilbert-transform to produce 175 000 image grids in 35 patients, labeled for rotational activation by experts who showed consistency but with variability (kappa [κ]=0.79). In each patient, ablation terminated AF. A CNN was developed and trained on 100 000 AF image grids, validated on 25 000 grids, then tested on a separate 50 000 grids. RESULTS: In the separate test cohort (50 000 grids), CNN reproducibly classified AF image grids into those with/without rotational sites with 95.0% accuracy (CI, 94.8%-95.2%). This accuracy exceeded that of support vector machines, traditional linear discriminant, and k-nearest neighbor statistical analyses. To probe the CNN, we applied gradient-weighted class activation mapping which revealed that the decision logic closely mimicked rules used by experts (C statistic 0.96). CONCLUSIONS: CNNs improved the classification of intracardiac AF maps compared with other analyses and agreed with expert evaluation. Novel explainability analyses revealed that the CNN operated using a decision logic similar to rules used by experts, even though these rules were not provided in training. We thus describe a scaleable platform for robust comparisons of complex AF data from multiple systems, which may provide immediate clinical utility to guide ablation. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02997254. Graphic Abstract: A graphic abstract is available for this article.

Mapping and Ablation of Rotational and Focal Drivers in Atrial Fibrillation.

Drivers are increasingly studied ablation targets for atrial fibrillation (AF). However, results from ablation remain controversial. First, outcomes vary between centers and patients. Second, it is unclear how best to perform driver ablation. Third, there is a lack of practical guidance on how to identify critical from secondary sites using different AF mapping methods. This article addresses each of these issues.

Reinvigorating the clinical examination for the 21st century.

At its most fundamental level, the clinical encounter between a patient and their doctor seeks to solve a mystery. Clinicians uncover clues through the history, physical examination, and ancillary tests to arrive at a diagnosis and develop a management plan. Despite advances in technology, the majority of clinical diagnoses are still reached through the history and physical examination without the use of laboratory and imaging tests. However, in the modern American hospital, clinicians spend as little as 12% of their time in direct contact with patients and their families. This has led to a decline in clinical examination skills and contributes to diagnostic error. There is a growing movement to return clinicians and trainees back to the bedside. In 2017, we formed the Society of Bedside Medicine to encourage innovation, education, and research on the role of the clinical encounter in 21st century medicine. Over the last 3 years, we have embraced the following 6 strategies to reinvigorate the practice of the clinical examination: 1) be present with the patient; 2) practice an evidence­based approach to the physical exam; 3) create opportunities for intentional practice of the physical exam; 4) recognize the power of the physical examination beyond diagnosis; 5) use point­of­care technology to aid in diagnosis and reinforce skills; and 6) seek and provide specific feedback on physical examination skills. By employing these strategies in both teaching and practice, clinicians can maximize the value of time spent with patients and renew the importance of the clinical examination in 21st century practice.