Effectiveness of atrial fibrillation on high-intensity transient signals to cerebral circulation during TAVI

Background Cerebral microemboliazations remain a major concern peri-operatively and following Transcatheter Aortic Valve Implantation (TAVI). We evaluated whether atrial fibrillation may predispose to an increased number of cerebrovascular emboli during the procedure. Purpose The aim of the study was to evaluate, using a transcranial doppler, the effect of atrial fibrillation on transient high-intensity signals to middle cerebral arteries during transcatheter aortic valve implantation. Methods Consecutive patients who underwent transfemoral TAVI with Evolut™ R bioprosthesis, were categorized into two groups. Group A patients with permanent atrial fibrillation (AF) on anticoagulation, Group B patients with sinus rhythm (SR). Dual antiplatelet therapy with aspirin and clopidogrel was administered to all patients 24 hours prior to the procedure at loading dose, with patients in Group A receiving in addition low-molecular-weight-heparin. The number of detected High Intensity Transient Signals (HITS) was assessed using Rimed Digi-Lite™ Transcranial Doppler on both cerebral arteries during the following phases of the procedure; Phase 0: 30 minutes prior to procedure initiation, Phase I: between access site puncture and introduction of the delivery system, Phase II: during the implantation of the bioprosthesis, until the removal of the delivery system. All implantations were performed without predilation. Furthermore, patients were evaluated by neurologist before TAVI and on discharge day. Safety was evaluated according to VARC-2 criteria. Results Twenty-eight patients were evaluated (81±6 years, 16 males (57.1%)). Group A had higher number of total (786±95 vs. 604±103, p=0.002) as well as Phase I HITS (393±94 vs. 285±86, p=0.002). One cerebrovascular event was recorded in Group A and one patient categorized to Group B developed major bleeding due to conversion to femoral surgical cut-down. The average number of received blood units, was higher in AF compared to SR Group (Group 1: 0.8±1.9 vs. Group 2: 0.5±0.7, p: 0.886), without however, reaching statistical significance. Conclusion Patients with atrial fibrillation had larger burden of embolic HITS during TAVI indicating high risk patients for embolic cerebrovascular events. This may has implications for future strategies for cerebral embolic protection. FUNDunding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Ippokrateio General Hospital of Athens

Unveiling the impact of fibrosis presence in fibrillatory electrograms

Introduction Complexity and fragmentation presence in atrial fibrillation (AF) electrograms (EGMs) has been extensively studied in the literature, with areas exhibiting complex fractionated atrial electrograms (CFAEs) postulated as responsible for AF maintenance. Computational simulations based on in silico models are widely employed to support AF initiating and maintenance theories. However, they are still limited when trying to mimic the effect of fibrosis in live cardiac cells and its impact in the clinical context, i.e., EGM morphologies in electroanatomical mapping studies. Controlled experiments on cultivated cardiomyocytes and optical mapping signals can better explain the role of fibrosis and its effect on EGM recordings. Purpose To study the effect of fibrosis in fibrillatory scenarios by comparing the temporal and frequency domains of EGMs and Ca2+ transient signals in cardiomyocyte cell cultures. Methods A total of 51 HL1 cardiomyocytes cell line monolayers experiments were cultured until confluence. Optical mapping (OM) was performed to evaluate the electrophysiological activity of the samples through Ca2+ transient quantification under the effect of Rhod2 dye. Activation frequency and calcium transient signals were acquired, and virtual EGMs were calculated from the signals virtually after post-processing the cell cultures at 16 different positions in the culture, see Figure 1A. Results The DF ratio between the OM and the virtual EGMs obtained for the different fibrosis levels are summarized and represented in Figure 1B. The Pearson's correlation coefficient was adjusted for all the samples and the significance level was stablished at p-value<0.01. Conclusions Optical mapping signal morphologies strongly correlate with EGM recordings when a clear dominant frequency (DF) dominates the complete area of the cell culture and no fibrosis is present. However, for patchy distributions of the DF, usually associated with higher concentrations of fibrosis, morphologies do not correlate for increasing fibrosis levels, and DF measurements differ with poor match between EGM-DF and OM-DF. Results on higher fibrotic experiments, i.e., 40–50% fibrosis level, show that DF correlates due to the poor and degraded cardiac activity in the EGMs and optical mapping recordings. The results reveal the importance and impact of fibrosis in the remodeling of atrial tissue and the correct interpretation of endocardial EGMs in the presence of heterogeneous tissue. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III and Ministerio de Ciencia, Innovaciόn y Universidades

Phasor Estimation of Transient Electrical Signals Composed of Harmonics and Interharmonics

Numerical relays have become essential tools for carrying out the protection and surveillance tasks of electrical power systems. These relays implement their functions from the phasors of the electrical network signals, estimated by digital processing using digital filters. Digital filters must meet certain requirements, such as providing a fast and effective response to increasingly complex transient signals made up of components that make the estimation process difficult. In addition to the decreasing exponential (decaying dc offset), harmonics, and signal noise, it must be added that the interharmonic components that in recent years have acquired great relevance, mainly because of the increase in non-linear loads and the extensive use of power electronic systems. The presence of these interharmonic components causes a poor response in most of the filters implemented today. This article presents the design of a new digital filter, C-CharmDF (Cleaned Characteristic Harmonic Digital Filter) for phasor estimation on noisy transient signals with decreasing exponential components, harmonics, and interharmonics. A detailed study was carried out for severe transient situations and stationary signals. It was found that the method can be suitable for relays that implement both fault location functions and system protection functions.