Search

In recent years, numerous applications for artificial intelligence (AI) in cardiology have been found, due in part to large digitized data sets and the evolution of high-performance computing. In the discipline of cardiac electrophysiology (EP), a number of clinical, imaging, and electrical waveform data are considered in the diagnosis, prognostication, and management of arrhythmias, which lend themselves well to automation through AI. But equally relevant, AI offers a unique opportunity to discover novel EP concepts and improve clinical care through its inherent, hierarchical tenets of self-learning. In this review we focus on the application of AI in clinical EP and summarize state-of-the art, large, clinical studies in the following key domains: (1) electrocardiogram-based arrhythmia and disease classification; (2) atrial fibrillation source detection; (3) substrate and risk assessment for atrial fibrillation and ventricular tachyarrhythmias; and (4) predicting outcomes after cardiac resynchronization therapy. Many are small, single-centre, proof-of-concept investigations, but they still show ground-breaking performance of deep learning, a subdomain of AI, which surpasses traditional statistical analysis. Larger studies, for instance classifying arrhythmias from electrocardiogram recordings, have further provided external validation of their high accuracy. Ultimately, the performance of AI is dependent on the quality of the input data and the rigour of algorithm development. The field is still nascent and several barriers will need to be overcome, including prospective validation in large, well labelled data sets and more seamless information technology-based data collection/integration, before AI can be adopted into broader clinical EP practice. This review concludes with a discussion of these challenges and future work., (Copyright © 2021 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: The safety and efficacy parameters for bipolar radiofrequency (RF) ablation are not well defined., Objective: The purpose of this study was to investigate the safe range of power, utility of transmyocardial bipolar electrogram (EGM) amplitude, and circuit impedance in ablation monitoring., Methods: Sixteen beating ex vivo human and swine hearts were studied in a Langendorff setup. Ninety-two bipolar ablations using two 4-mm irrigated catheters were performed at settings of 20-50 W, 60 seconds, and 30 mL/min irrigation in the left ventricle., Results: For low-power ablations (20 and 30 W), transmurality was observed in 29 of 38 (76%) and 10 of 28 (36%) ablations for tissue thickness ≤17 mm and >17 mm, respectively. For high-power ablations (40 and 50 W), transmurality was observed in 5 of 7 (71%) and 7 of 19 (37%) ablations for tissue thickness ≤17 mm and >17 mm, respectively. Steam pop occurrence for low- and high-power ablations was 11 of 66 (16%) and 16 of 26 (62%), respectively (P = .0001), respectively. Lesion depth (limited by transmurality) was 12.0 ± 5.7 mm and 12.3 ± 5.8 mm, respectively (P = 1). Transmyocardial EGM amplitude decrement >60% strongly predicted transmurality (area under the curve [AUC] 0.8), and circuit impedance decrement >26% predicted steam pops (AUC 0.75). Half-normal saline did not affect transmurality or incidence of steam pops compared to normal saline irrigation., Conclusion: Bipolar RF ablation at power of 20-30 W provided an ideal balance of safety and efficacy, whereas power ≥40 W should be used with caution due to the high incidence of steam pops. Lesion transmurality monitoring and steam pop avoidance were best achieved using transmyocardial bipolar EGM voltage and circuit impedance, respectively., (Copyright © 2021 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Multiple decades of work have recognized complexities of substrates responsible for ventricular tachycardia (VT). There is sufficient evidence that 3 critical components of a re-entrant VT circuit, namely, region of slow conduction, zone of unidirectional block, and exit site, are located in spatial vicinity to each other in the ventricular scar. Each of these components expresses characteristic electrograms in sinus rhythm, at initiation of VT, and during VT, respectively. Despite this, abnormal electrograms are widely targeted without appreciation of these signature electrograms during contemporary VT ablation. Our aim is to stimulate physiology-based VT mapping and a targeted ablation of VT. In this article, we focus on these 3 underappreciated aspects of the physiology of ischemic scar-related VT circuits that have practical applications during a VT ablation procedure. We explore the anatomic and functional elements underlying these distinctive bipolar electrograms, specifically the contribution of tissue branching, conduction restitution, and wave curvature to the substrate, as they pertain to initiation and maintenance of VT. We propose a VT ablation approach based on these 3 electrogram features that can be a potential practical means to recognize critical elements of a VT circuit and target ablation., (Copyright © 2020 Heart Rhythm Society. All rights reserved.)

Background: Intraoperative mapping has demonstrated focal activations during human atrial fibrillation (AF). These putative AF sources can manifest sustained periodic bipolar and unipolar QS electrograms (EGMs). We have automated the detection of these EGM features using our validated Focal Source and Trigger (FaST) computational algorithm., Objective: The purpose of this study was to conduct a randomized controlled pilot evaluating the feasibility and efficacy of FaST mapping/ablation as an adjunct to pulmonary vein isolation (PVI) in reducing AF recurrence., Methods: We randomized 80 patients with high-burden paroxysmal or persistent AF (age 61 ± 10 years; 75% male) to PVI alone (n = 41) or PVI+FaST mapping/ablation (n = 39). The primary endpoint was time to AF recurrence >30 seconds between 3 and 12 months after 1 procedure., Results: FaST sites were identified in all but 1 patient and were localized to pulmonary vein (PV) (2.1 ± 1.1 per patient) and extra-PV regions (2.8 ± 1.4 per patient). FaST mapping and ablation times were 27 ± 9 minutes and 8.5 ± 5 minutes, respectively. Patients with AF termination during ablation had greater AF cycle length prolongation with PVI+FaST than PVI (Δ20 ± 14 ms vs Δ5 ± 17 ms; P = .046). Freedom from AF recurrence at 12 months was higher in PVI+FaST vs PVI for patients off antiarrhythmic drugs (74% vs 51%; hazard ratio 0.48; 95% confidence interval 0.21-1.08; P = .064) but did not quite reach statistical significance. Major adverse events were similar between the 2 groups., Conclusion: In this randomized controlled pilot, real-time FaST mapping provided an intuitive, automated approach for localizing focal AF sources. FaST ablation as an adjunct to PVI may reduce AF recurrence, which requires verification with a larger multicenter trial., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The ventricular tachycardia (VT) circuit is often assumed to be located in the endocardium or epicardium. The plateauing success rate of VT ablation warrants reevaluation of this mapping paradigm., Objective: The purpose of this study was to resolve the intramural components of VT circuits by mapping in human hearts., Methods: Panoramic simultaneous endocardial-epicardial mapping (SEEM) during intraoperative mapping (IOM) was performed in human subjects. In explanted hearts (EH), SEEM and intramural multielectrode plunge needle mapping (NM) of the left ventricle were performed. Overall, 37 VTs (26 ischemic cardiomyopathy [ICM], 11 nonischemic cardiomyopathy [NICM]) were studied in 32 patients. Intraoperative SEEM was performed in 16 patients (16 ICM). Additionally, 16 explanted myopathic human hearts (9 NICM, 7 ICM) were studied in a Langendorff setup. Predominant intramural location of the VT was imputed by the absence of significant endocardial-epicardial activation during IOM (using SEEM and no NM) or by the presence of intramural activation spanning the entire cycle length (including mid-diastole) in EH (SEEM and NM)., Results: By IOM (SEEM), predominant endocardial activation (entire tachycardia cycle length including mid-diastolic activation) was present in 10 of 18 VTs (55%). In 8 of 18 VTs (44%), the VT circuit was presumed to be intramural due to incomplete diastolic activation in endocardium and epicardium. In EH (SEEM and NM), VT location was predominantly intramural, endocardial, and epicardial in 8 of 19 (42%), 5 of 19 (26%), and 1 of 19 VTs (5%), respectively., Conclusion: In a significant proportion of both ischemic and nonischemic ventricular tachycardias, the predominant activation was located in the intramural space., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Local bipolar electrogram (EGM) peak-to-peak voltage (Vpp) is currently used to characterise mapped myocardial substrate. However, how interelectrode distance and angle of wavefront incidence affect bipolar, Vpp values, in the current era of multi-electrode mapping is unknown., Objectives: To elucidate the effects of tissue and electrode geometry on bipolar Vpp measurements, when mapping healthy versus diseased atrial regions., Methods: A bidomain model of human atrial tissue was used to quantify the influence on Vpp values of various electrode configurations in healthy tissue, and tissue containing an unexcitable region. The orientation angle and interelectrode spacing of a surface bipole, and thickness and depth of the unexcitable core were serially varied. Results were validated with data obtained from isolated porcine hearts., Results: In healthy tissue, bipolar Vpp values increased with increasing interelectrode spacing and plateaued beyond a spacing of approximately 4 mm. The bipolar Vpp values in healthy tissue were relatively less sensitive to wavefront orientation angle with large interelectrode spacing. In diseased tissue, on the contrary, with increasing interelectrode spacing, bipolar Vpp values increased linearly without a plateau and were more sensitive to orientation angle. The bipolar Vpp values decreased with increasing thickness of the scar, with larger relative decrease in small bipoles than larger ones. Bipolar Vpp values increased with a progressively intramural location of fixed-size scar and became less distinguishable from healthy tissue especially for smaller interelectrode spacings., Conclusions: The scalable relationship established for interelectrode distances favour an electric-field-based assessment as opposed to traditional Vpp values as a tool for physiologically relevant measurement for mapping catheters with interelectrode spacing up to 4 mm. This will allow for universal assessment of myocardial health across catheters with varied spacing., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Decremental response evoked with extrastimulation (DEEP) is a useful tool for determining diastolic return path of ventricular tachycardia (VT). Though a targeted VT ablation is feasible with this approach, determinants of DEEP response have not been studied OBJECTIVES: To elucidate the effects of clinically relevant factors, specifically, the proximity of the stimulation site to the arrhythmogenic scar, stimulation wave direction, number of channels open in the scar, size of the scar and number of extra stimuli on decrement and entropy of DEEP potentials., Methods: In a 3-dimensional bi-domain simulation of human ventricular tissue (TNNP cell model), an irregular subendocardial myopathic region was generated. An irregular channel of healthy tissue with five potential entry branches was shaped into the myopathic region. A bipolar electrogram was derived from two electrodes positioned in the centre of the myopathic region. Evoked delays between far-field and local Electrogram (EGM) following an extrastimulus (S1-S2, 500-350 ms) were measured as the stimulation site, channel branches, and inexcitable tissue size were altered., Results: Stimulation adjacent to the inexcitable tissue from the side opposite to the point-of-entry produces longest DEEP delay. The DEEP delay shortens when the stimulation point is farther away from the scar, and it decreases maximally when stimulation is done from a site beside a conduction barrier. Entropy increases with S2 when stimulation site is from farther away. An unprotected channel structure with multiple side-branch openings had shorter DEEP delay compared to a protected channel structure with a paucity of additional side-branch openings and a point-of-entry on the side opposite to the pacing source. Addition of a second shorter extrastimulus did not universally lead to higher DEEP delay CONCLUSIONS: Location and direction of the wavefront in relation to scar entry and size of scar determine the degree of evoked response while the number of extrastimuli has a small additional decremental effect., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objective: To compare the pulp reactions in terms of pulp inflammation, leakage involving bacteria and reactionary dentin formation to total-etch adhesive, Prime & Bond NT and self-etch adhesive, Xeno III in 2 mm deep class V cavities prepared in human teeth., Study Design: 2 mm deep class V cavities were prepared on buccal surface of 40 human premolars. The teeth were randomly divided into two groups based on the application of a total-etch adhesive system, Prime and Bond NT after acid etching or a self-etching adhesive system, Xeno III. The teeth were extracted after 7 and 30 days and prepared according to routine histological techniques., Results: All teeth were asymptomatic. Both the adhesives showed moderate to severe inflammatory reactions in few cases initially at seven days, but the response was generally minimal at 30 days. Leakage involving bacteria was detected in 42.5% of restorations and 40% of the specimens were associated with various grades of pulp inflammation. The cavity remaining dentin thickness influenced the grade of inflammatory activity. A significant correlation was detected between inflammatory cell response and the presence of bacteria. Pulp response to self-etching adhesive, Xeno III was minimally different from that of the total-etch adhesive, Prime & Bond NT (p < .05)., Conclusions: A self-etching adhesive system, Xeno III showed similar pulp response and leakage involving bacteria to a total-etch adhesive, Prime & Bond NT. Both adhesives showed an acceptable biological compatibility with human pulps at 30 days.

An antiserum, obtained by immunising rabbits with a human peptide-protein conjugate, was shown to inhibit histamine release from rat mast cells both in vitro and in vivo. Immunisation of sensitised rats with the same peptide reduced IgE antibody formation and serum histamine concentration, and abolished systemic anaphylactic reactions in response to allergen challenge. This peptide may form the basis of a vaccine in a new approach to the immunotherapy of atopic disease.

The effect of continuous release of microquantities of cyproterone acetate from subcutaneously implanted silastic capsules on the fertility of surgically manipulated seminal vesicles of rat has been studied. The experimental animals showed infertility for 3 weeks, as a consequence of removal of seminal plasma, following which normal fertility returns as efficiently as that operated control. However, a significant decrease in weight of the testes and epididymides, were recorded. It appears that seminal vesicles can synthesize seminal plasma even at very low levels of androgen in the presence of cyproterone acetate.