Delay Block Research Articles

Multicenter Hemodynamic Assessment of the LOT-CRT Strategy: When Does Combining Left Bundle Branch Pacing and Coronary Venous Pacing Enhance Resynchronization?: Primary Results of the CSPOT Study.

Left bundle branch area pacing (LBBAP) may be an alternative to biventricular pacing (BVP) for cardiac resynchronization therapy (CRT). We sought to compare the acute hemodynamic and ECG effects of LBBAP, BVP, and left bundle-optimized therapy CRT (LOT-CRT) in CRT candidates with advanced conduction disease. In this multicenter study, 48 patients with either nonspecific interventricular conduction delay (n=29) or left bundle branch block (n=19) underwent acute hemodynamic testing to determine the change in left ventricular pressure maximal first derivative (LV dP/dtmax) from baseline atrial pacing to BVP, LBBAP, or LOT-CRT. Atrioventricular-optimized increases in LV dP/dtmax for LOT-CRT (mean, 25.8% [95% CI, 20.9%-30.7%]) and BVP (26.4% [95% CI, 20.2%-32.6%]) were greater than unipolar LBBAP (19.3% [95% CI, 15.0%-23.7%]) or bipolar LBBAP (16.4% [95% CI, 12.7%-20.0%]; P≤0.005). QRS shortening was greater in LOT-CRT (29.5 [95% CI, 23.4-35.6] ms) than unipolar LBBAP (11.9 [95% CI, 6.1-17.7] ms), bipolar LBBAP (11.7 ms [95% CI, 6.4-17.0]), or BVP (18.5 [95% CI, 11.0-25.9] ms), all P≤0.005. Compared with patients with left bundle branch block, patients with interventricular conduction delay experienced less QRS reduction (P=0.026) but similar improvements in LV dP/dtmax (P=0.29). Bipolar LBBAP caused anodal capture in 54% of patients and resulted in less LV dP/dtmax improvement than unipolar LBBAP (18.6% versus 23.7%; P<0.001). Subclassification of LBBAP capture (EHRA criteria) indicated LBBAP or LV septal pacing in 27 patients (56%) and deep septal pacing in 21 patients (44%). The hemodynamic benefit of adding left ventricular coronary vein pacing to LBBAP depended on baseline QRS duration (P=0.031) and success of LBBAP (P<0.004): LOT-CRT provided 14.5% (5.0%-24.1%) greater LV dP/dtmax improvement and 20.8 (12.8-28.8) ms greater QRS shortening than LBBAP in subjects with QRS ≥171 ms and deep septal pacing capture type. In a CRT cohort with advanced conduction disease, LOT-CRT and BVP provided greater acute hemodynamic benefit than LBBAP. Subjects with wider QRS or deep septal pacing are more likely to benefit from the addition of a left ventricular coronary vein lead to implement LOT-CRT. URL: https://www.clinicaltrials.gov; Unique identifier: NCT04905290.

Multicenter hemodynamic assessment of the LOT-CRT strategy: when is one lead enough for resynchronization?

Abstract Background Left bundle branch area pacing (LBBAP) has been postulated as an alternative to traditional cardiac resynchronization therapy via biventricular pacing (BiV) in heart failure patients with wide QRS. Limited data is available regarding the acute hemodynamic response of LBBAP and the combination of LBBAP and coronary venous (LVcv) pacing (LOT-CRT). Purpose We sought to compare the acute hemodynamic and ECG effects of traditional CRT (BiV or LV-only) versus LBBAP and LOT-CRT in CRT candidates with advanced conduction disease. Methods In this multi-centre study (5 EU and 7 US centres), 48 subjects (mean age 65.8 years, 67% males, LV ejection fraction 29.4%) with either nonspecific interventricular conduction delay (NIVCD, n = 29) or left bundle branch block (LBBB; n =19; based upon strict criteria AHA/ACC/HRS plus Strauss) underwent an acute hemodynamic study to determine the % change in +LV dP/dtmax from baseline atrial pacing versus BiV, LBBAP, or LOT-CRT. Each therapy pacing configuration was applied 4 times at 5 different atrioventricular (AV) delays. QRS shortening was assessed using standard 12-lead ECG. Results Successful LBBAP lead implantation was achieved in 27 patients (56%) using current EHRA criteria. Twenty-one patients (44%) were categorized as deep septal pacing (DSP), due to suboptimal lead penetration or advanced left conduction system disease with broad paced QRS complexes and absent V1-r-wave. The increase in AV-optimized dP/dtmax for the different pacing configurations is displayed in the Figure, left panel. LOT-CRT dP/dtmax % improvement was 25.8%, significantly higher than LBBAP configurations (p&amp;lt;0.01), either unipolar-LBBAP (19.3%), or bipolar-LBBAP (16.4%), but not different from BiV (26.4%). QRS shortening was greater in LOT-CRT (29.5ms) vs. unipolar-LBBAP (11.9ms), bipolar-LBBAP (11.7ms), or BiV (18.5ms), all p&amp;lt;0.01. Sub-group analysis indicated the hemodynamic benefit of adding LVcv pacing when LBBAP strategy was pursued (Figure, right panel) depended on obtaining LBBAP rather than DSP (p &amp;lt; 0.01) and baseline QRS duration (p = 0.03). The largest benefit was observed among subjects with a baseline QRS wider than the observed cohort mean (171ms) and DSP only, where LOT-CRT provided 14.5% (5.0-24.1%) greater dP/dtmax improvement and 20.8ms (12.8-28.8ms) greater QRS duration shortening than unipolar DSP. Conclusions In a CRT cohort with advanced conduction disease, LOT-CRT provided greater acute hemodynamic benefit than LBBAP strategy (i.e. including also DSP cases). Patients with wider QRS or suboptimal outcome of LBBAP strategy (DSP) are more likely to benefit from addition of a LVcv lead to implement LOT-CRT.Figure 1

Effects of delay sequence in a delay discounting task

Delay discounting refers to the decrease in subjective value of a reward as the delay until its receipt increases. In the present study we assessed the effects of the sequence of delay blocks (increasing or decreasing) on discounting and the data systematicity using a titrating procedure with human participants. All participants completed the delay discounting task in both an increasing and decreasing sequence of delays. Delays ranged from one day to ten years. We found steeper discounting when the delays were presented in an increasing sequence compared with when they were presented in a decreasing sequence. We also found steeper discounting when participants completed the increasing sequence condition first. Our results agree with other findings reported in the literature and suggest that delay discounting may be affected by prior and subsequent experience.

Methylphenidate, but not citalopram, decreases impulsive choice in rats performing a temporal discounting task.

Drugs targeting monoamine systems remain the most common treatment for disorders with impulse control impairments. There is a body of literature suggesting that drugs affecting serotonin reuptake and dopamine reuptake can modulate distinct aspects of impulsivity - though such tests are often performed using distinct behavioral tasks prohibiting easy comparisons. Here, we directly compare pharmacologic agents that affect dopamine (methylphenidate) vs serotonin (citalopram) manipulations on choice impulsivity in a temporal discounting task where rats could choose between a small, immediate reward or a large reward delayed at either 2 or 10s. In control conditions, rats preferred the large reward at a small (2s) delay and discounted the large reward at a long (10s) delay. Methylphenidate, a dopamine transport inhibitor that blocks reuptake of dopamine, dose-dependently increased large reward preference in the long delay (10s) block. Citalopram, a selective serotonin reuptake inhibitor, had no effect on temporal discounting behavior. Impulsive behavior on the temporal discounting task was at least partially mediated by the nucleus accumbens shell. Bilateral lesions to the nucleus accumbens shell reduced choice impulsivity during the long delay (10s) block. Following lesions, methylphenidate did not impact impulsivity. Our results suggest that striatal dopaminergic systems modulate choice impulsivity via actions within the nucleus accumbens shell, whereas serotonin systems may regulate different aspects of behavioral inhibition/impulsivity.

Design and FPGA Implementation of 4×4 Vedic Multiplier using Different Architectures

The need of high speed multiplier is increasing as the need of high speed processors are increasing. A Multiplier is one of the key hardware blocks in most of the fast processing systems which is not only a high delay block but also a major source of power dissipation. A conventional processor requires substantially more hardware resources and processing time in the multiplication operation, rather than addition and subtraction. This Project describes about the design of 4-bit, 8-bit and 32-bit Vedic multiplier using ancient Vedic mathematics which helps in delay and power reduction. Simulation is done in Xilinx VIVADO software using VHDL and display on LCD. The results for Vedic multiplier using various architecture and their delay comparison are done. Key Words: FPGA (Artix-7), adders, 4x4 Array Multiplier, Vedic Mathematics

Proof-of-concept model for instantaneous heart rate-drift correction during low and high exercise exertion.

Introduction: This study aimed to model below and above anaerobic threshold exercise-induced heart rate (HR) drift, so that the corrected HR could better represent kinetics during and after the exercise itself. Methods: Fifteen healthy subjects (age: 28 ± 5 years; : 50 ± 8 mL/kg/min; 5 females) underwent a maximal and a 30-min submaximal (80% of the anaerobic threshold) running exercises. A five-stage computational (i.e., delay block, new training impulse-calculation block, Sigmoid correction block, increase block, and decrease block) model was built to account for instantaneous HR, fitness, and age and to onset, increase, and decrease according to the exercise intensity and duration. Results: The area under the curve (AUC) of the hysteresis function, which described the differences in the maximal and submaximal exercise-induced and HR kinetics, was significantly reduced for both maximal (26%) and submaximal (77%) exercises and consequent recoveries. Discussion: In conclusion, this model allowed HR drift instantaneous correction, which could be exploited in the future for more accurate estimations.

Biatrial arrhythmogenic substrate in patients with hypertrophic obstructive cardiomyopathy

BackgroundAtrial fibrillation (AF) in patients with hypertrophic obstructive cardiomyopathy (HOCM) may be caused by a primary atrial myopathy. Whether HOCM-related atrial myopathy affects mainly electrophysiological properties of the left atrium (LA) or also the right atrium (RA) has never been investigated. ObjectiveThe purpose of this study was to characterize atrial conduction and explore differences in the prevalence of conduction disorders, potential fractionation, and low-voltage areas (LVAs) between the RA and LA during sinus rhythm (SR) as indicators of potential arrhythmogenic areas. MethodsIntraoperative epicardial mapping of both atria during SR was performed in 15 HOCM patients (age 50 ± 12 years). Conduction delay (CD) and conductin block (CB), unipolar potential characteristics (voltages, fractionation), and LVA were quantified. ResultsConduction disorders and LVA were found scattered throughout both atria in all patients and did not differ between the RA and LA (CD: 2.9% [1.9%–3.6%] vs 2.6% [2.1%–6.4%], P = .541; CB: 1.7% [0.9%–3.1%] vs 1.5% [0.5%–2.8%], P = .600; LVA: 4.7% [1.6%–7.7%] vs 2.9% [2.1%–7.1%], P = .793). Compared to the RA, unipolar voltages of single potentials (SPs) and fractionated potentials (FPs) were higher in the LA (SP: P75 7.3 mV vs 10.9 mV; FP: P75 2.0 mV vs 3.7 mV). FP contained low-voltage components in only 18% of all LA sites compared to 36% of all RA sites. ConclusionIn patients with HOCM, conduction disorders, LVA, and FP are equally present in both atria, supporting the hypothesis of a primary atrial myopathy. Conceptually, the presence of a biatrial substrate and high-voltage FP may contribute to failure of ablative therapy of atrial tachyarrhythmias in this population.

Management of Postprocedural Conduction Disturbances Using a Prespecified Algorithm in the Optimize PRO Study

BackgroundLack of standardization in posttranscatheter aortic valve replacement (TAVR) conduction disturbance (CD) identification and treatment may affect permanent pacemaker implantation (PPI) rates and clinical outcomes. The safety and efficacy of a standardized TAVR CD algorithm has not been analyzed. This study analyzes the Optimize PRO post-TAVR CD management algorithm with Evolut PRO/PRO+ valves. MethodsOptimize PRO is a prospective, postmarket study implementing 2 strategies to reduce pacemaker rates: TAVR with cusp overlap technique and a post-TAVR CD algorithm. The 2-hour postprocedural electrocardiogram (ECG) stratified patients to early discharge in the absence of new ECG changes or to CD algorithms for (1) ECG changes with preexisting right or left bundle branch block (LBBB), interventricular conduction delay or first-degree atrioventricular block, (2) new LBBB, or (3) high-degree atrioventricular block (HAVB). ResultsThe interim analysis of the CD cohort consisted of 125/400 TAVR recipients. In the CD cohort, the 30-day new PPI rate was higher (28.1% vs 1.5%; P <.001), and 60 (48%) patients were discharged with a 30-day continuous ECG monitor. At 30 days, 90% of patients discharged with a monitor did not require PPI. Clinical outcomes, including mortality, stroke, bleeding, and reintervention, were similar in patients with and without CDs. No patient experienced sudden cardiac death. ConclusionsEffective management of CDs using a standard algorithm following Evolut TAVR provides similar 30-day safety outcomes to patients without CDs who undergo routine next day discharge. The CD algorithm may provide an effective strategy to recognize arrhythmias early, improve PPI utilization, and facilitate safe monitoring of patients after discharge.

Enhanced Position Estimation Based on Frequency Adaptive Generalized Comb Filter for Interior Permanent Magnet Synchronous Motor Drives

Accurate rotor position estimation is critical to ensure the high-performance operation of position sensorless interior permanent magnet synchronous motor (IPMSM) drives. However, the back electromotive force (BEMF) estimated by the model-based observers is usually nonideal, which may further degrade the position estimation accuracy. In this paper, a frequency adaptive generalized comb filter (FAGCF) with a quadrature phase-locked loop (PLL) is adopted to suppress the rotor position estimation errors by filtering out the dominant distortions in the BEMF, including the (6k±1)th harmonics caused by inverter nonlinearity and flux spatial harmonics, as well as the DC offset from the inaccurate current measurements. This proposed filter is constructed by multiple digital delay blocks and therefore has the advantage of easy implementation with less online parameters tuning effort. Meanwhile, a linearized model is derived for PLL parameter design, with which the stability of the FAGCF-PLL position estimation system can also be analyzed theoretically. The effectiveness of the proposed sensorless control strategy has been validated with the experimental results on a 1.5-kW IPMSM drive.

Fluctuations in alpha and beta power provide neural states favourable for contextually relevant anticipatory processes.

Cued sensory input occasionally fails to immediately ensue its respective trigger. Given that our environments are rich in sensory cues, we often end up processing other contextually relevant information in the meantime. The experimental design of the present study allowed us to investigate how such temporal delays and visual interferences may impact anticipatory processes. Thirty-four participants were trained to remember an individualised set of eight paired-up faces. These paired-up faces were presented pseudorandomly in sequences of unpaired face images. To keep participants engaged throughout the electroencephalography study, they were instructed to classify each face image, according to its sex, as fast as possible without compromising accuracy. We observed dissimilar modulations in alpha and beta power between the 6-s timeframe encompassing the onsets of predictive and expected images (temporal delay block) and the 6-s timeframe encompassing the predictive, interference and expected images (visual interference block). Furthermore, an expectation-facilitated reduction of the face-sensitive N170 component was only observed if an anticipated face image directly followed its corresponding predictive counterpart. This effect was no longer evident when the expected face was preceded by a distracting face image. Regardless of the block type, behavioural measures confirmed that anticipated faces were classified significantly faster and with fewer erroneous responses than faces not foretold by a predictive face. Collectively, these results demonstrate that whilst the brain continuously adjusts internal hierarchical generative models to account for temporal delays in stimulus onset and visual interferences, the higher levels, and subsequent predictions, fundamental for expectation-facilitated behaviours remain intact.

Optimisation of decrementing evoked potential mapping for functional substrate identification in ischaemic ventricular tachycardia ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Decrement evoked potential (DeEP) mapping has been shown to identify the functional substrate critical to the Ventricular Tachycardia (VT) circuit with a higher specificity than late potential mapping.[1] However, there is limited data on methodological optimisation of this technique which could identify more relevant regions of conduction delay and functional block that occurs during clinical VT by activating the substrate at coupling intervals closer to the VT cycle length (CL). Purpose The goal of this study was to investigate a range of short coupled extra-stimuli and decrement thresholds to improve DeEP mapping target identification in patients with ischaemic cardiomyopathy. Methods Thirteen patients (70±12 years) underwent VT ablation. Mapping was performed with the Advisor HD Grid multipolar catheter. Maps were generated using omnipolar electrograms (EGMs). DeEP mapping was performed using 3 different extra-stimuli (S2) sequentially in each case: (1) 400 ms (DeEP-400); (2) VT cycle length (VTCL); (3) ventricular effective refractory period (VERP) + 20 ms. For each of the DeEP-400, DeEP-VTCL and DeEP-VERP maps, the definition of a DeEP was altered from the standard 10 ms decrement to multiple thresholds of 10 ms to 50 ms in 10 ms increments (figure 1). DeEP maps were compared to the VT exit site identified with VT activation maps. All patients underwent DeEP-400 focused ablation. Results All patients had 1 clinical VT (VTCL = 353 ± 48 ms; VERP + 20 ms = 300 ± 20 ms). Mean left ventricular ejection fraction was 30 ± 12 %. Sensitivity and specificity analyses (figure 2) show the optimal threshold for defining a DeEP is with an EGM prolongation of ≥ 20 ms for the DeEP-400 (sens. 77%, spec. 79%, ROC AUC 0.84), DeEP-VTCL (sens. 77%, spec. 79%, ROC AUC 0.83) and DeEP-VERP (sens. 69%, spec. 74%, ROC AUC 0.76) maps. Proportional to total mapped area, the DeEP-400 map area was significantly smaller than DeEP-VERP map area (19.0 ± 7.6 % vs 26.4 ± 14.3%; p=0.02). Delivering the S2 at the conventional VERP + 20 ms using a 10 ms decrement definition yielded a sensitivity of 84.6% and a specificity of 62.0% with a target ablation area of 33.9 cm2. With the optimised protocol of delivering the S2 at 400 ms using a 20 ms decrement definition, the sensitivity remains high at 76.9% with an improved specificity of 79.0%, thus reducing the ablation target area by 50% to 16.8 cm2. 92% patients were free of any VT after DeEP-400 guided ablation at 6-month median follow-up. Conclusion In this prospective, mechanistic study utilising omnipolar technology to explore a range of S2 extra-stimuli and decrement thresholds, DeEPs were optimally defined by a conduction delay of ≥ 20 ms with an S2 extra-stimulus coupling interval of 400 ms or VTCL to more accurately localise the VT exit site. This optimised DeEP mapping protocol further refines identification of the critical myocardial sites involved in the initiation and maintenance of VT.

Ventricular Parasystole in Cardiomyopathy Patients: A Link Between His-Purkinje System Damage and Ventricular Fibrillation

BackgroundThe clinical relevance and prognostic implications of ventricular parasystole are unknown. ObjectivesThis study sought to assess the prevalence of ventricular parasystole in patients with implantable cardioverter-defibrillators (ICDs) and ventricular parasystole’s association with ventricular arrhythmias and conduction system abnormalities. MethodsThis study retrospectively evaluated patients who underwent ICD interrogation at a single center between June 1, 2019, and August 31, 2020, and reviewed all available ICD and electrocardiogram data. This study identified patients with ventricular parasystole and compared the prevalence of ventricular fibrillation (VF), ventricular tachycardia (VT), and new conduction system abnormalities in those with ≥5 years of intrinsic QRS-complex electrocardiograms to those without parasystole. ResultsThis study included 374 patients (age 57 ± 21 years, 72% male, 45% nonischemic, 32% ischemic cardiomyopathy), of which, 104 (28%) had VT only, 39 (10%) VF only, and 10 (3%) both VT/VF. Ventricular parasystole was identified in 33 patients (9%); parasystolic foci were predominantly from the His-Purkinje system. Compared with those without parasystole, patients with parasystole had a significantly higher rate of VF (36% vs 11%; P < 0.01), but not VT (42% vs 29%; P = 0.12). Patients with parasystole, compared with those without parasystole, had a higher prevalence of new conduction abnormalities, particularly progressive intraventricular conduction delay (11 of 18 [61%] vs 12 of 83 [14%]; P < 0.01) and new right bundle branch block (4 of 18 [22%] vs 1 of 83 [1%]; P < 0.01). ConclusionsVentricular parasystole was strongly associated with new conduction system abnormalities and VF in patients who have cardiomyopathy with ICDs, suggesting a potential link between VF and His-Purkinje damage in this patient population.

Block workshop spatial scheduling based on cellular automata modelling and optimization

AbstractBlock fabrication is the process that has the greatest impact on shipbuilding efficiency, so block spatial scheduling is widely studied as the key to improving shipbuilding efficiency. The shipbuilding spatial scheduling problem addresses the coupling characteristics of time and space. It is difficult to balance these two aspects. Based on the characteristics of spatial scheduling problems in shipbuilding enterprises, a three‐dimensional space that uses time as the third dimension is imported, and a cellular automata model along with some evolutionary rules is built, which includes shape optimization rules, cluster or edge rule‐based layout rules, and First Come First Service dispatching rules. The objectives are to achieve the minimum total completion time, the largest utilization of space and machine, and the least number of delay blocks. Taking the real data in a block workshop of a shipbuilding enterprise as an example, the feasibility and effectiveness of the algorithm are verified by comparing the statistical analysis with other algorithms.

Performance enhancement of duobinary modulation-based DWDM system using particle swarm optimization

Abstract The next-generation light wave communication DWDM networks can accommodate large number of channels to efficiently utilize the bandwidth (BW). However, in the deployment of DWDM system mixing of two or more waves limits the performance due to four wave mixing (FWM) nonlinearity in fiber. This article, presents improved performance analysis of DWDM using a proposed improved duobinary modulation (IDBM), modified duobinary modulation (MDBM) and duobinary modulation (DBM) model for mitigation of FWM nonlinearities has been estimated experimentally through interference of noise on optical signal, FWM efficiency, FWM power etc. In IDBM, a unit delay in addition to time delay parameter is also utilized for generation of electrical duobinary pulses. The parameters of both delay blocks are tuned through particle swarm optimization (PSO) technique to improve the performance. The overall proposed IDBM effectively decreases the FWM. The results obtained for IDBM in terms of Q-factor 8.9, OSNR 18 dB, FWM power −87 dBm and FWM efficiency −70 dB shows substantial improvement with the recommended IDBM technique in comparison to DBM and MDBM schemes.

Fractional order active disturbance rejection control design for non-integer order plus time delay models

This paper proposes a time-delayed fractional order active disturbance rejection control (TD-FADRC) strategy to address a class of time-delayed fractional order systems represented by non-integer order plus time delay (NIOPTD) models. To accurately estimate the fractional order states, the fractional order extended state observer (FESO) is utilized with introducing an artificial delay block to synchronize inputs. The studied model and its corresponding observer are treated as a holistic plant, based on which several types of fractional order proportional-integral-derivative (FPID) with constrained order are employed as feedback controllers. By unfolding the resulting open-loop plant in the frequency domain, the controller gains can be derived explicitly from the typical robustness metrics, that is, the phase margin and gain crossover frequency. The performance, robustness, and delay issue are consequently all concerned. To guarantee the closed-loop stability, the controller gains under a given observer bandwidth are limited within a bounded region mapped by the D-decomposition method. Through representative simulations, the merits of the proposed strategy for such models are revealed.

A Cascaded Integral Action Based Filter for Distorted Conditions

This article proposes a cascaded integral action-based filter by relying on the orthogonal output of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/4$</tex-math></inline-formula> delay block. The proposed filter employs an integrator together with mechanisms involving feedback of the filtered signal and feedforward of its orthogonal input. Based on this approach, the proposed filter addresses the problem of initial state when applying a direct integral action to a sinusoidal voltage. More so, the proposed filter provides notch filtering characteristics at certain harmonic frequencies, thereby achieving improved harmonic rejection in comparison to existing second-order generalized integrator filter. Without frequency adaptivity, the proposed filter achieves fast response, and more importantly, provides excellent filtering of harmonic components at off-nominal frequencies of the supply voltage. Furthermore, dc-offset rejection in the proposed filter is considered together with its FLL implementation for frequency, phase angle, and amplitude estimations. Linearized model and stability evaluation of the proposed filter’s FLL are presented while detailed analytical, simulation, and experimental validation of the proposed filter’s performance for applications involving voltage parameter estimation for synchronization purposes and reference signal generation are provided. Results obtained demonstrate superiority of the proposed filter in terms of harmonic rejection and estimation speed when compared to existing filtering techniques.

Digital Noise-Cancellation Circuit Implementation Using Proposed Algorithm and Karnaugh Map in a MASH 2-1 Delta-Sigma Modulator

This paper presents the implementation of two digital noise-cancellation circuits (DNCCs) using a proposed algorithm and a Karnaugh map for a [Formula: see text] multistage noise-shaping (MASH) delta-sigma modulator (DSM). The MASH architecture inherits a superior signal-to-noise-and-distortion ratio (SNDR) with the aid of an efficient noise-cancellation technique either in the analogue or digital domain. The key motivation of this study was to design an area-efficient DNCC. The first approach employed a proposed algorithm (Algorithm-based DNCC) to implement the DNCC and to construct a delay block with an inverter and transmission gate. The second approach involved a Karnaugh map (K-map DNCC) and a delay block with a pair of D flip-flops. A maximum simulated signal-to-noise ratio of 135[Formula: see text]dB was completed with optimal analogue scaling coefficients for the proposed [Formula: see text] MASH DSM with DNCC. The simulated SNDRs of the Algorithm-based DNCC and K-map DNCC were 91.04[Formula: see text]dB and 91.16[Formula: see text]dB, respectively. Measured results show that the SNDR of the Algorithm-based DNCC, the SNDR of the K-map DNCC, power consumption and core area are approximately 58.7[Formula: see text]dB, 62.1[Formula: see text]dB, 0.26[Formula: see text][Formula: see text]W and 2275[Formula: see text][Formula: see text]m2, respectively, for the designed DNCCs with an operating frequency of 10.24[Formula: see text]MHz and supply voltage of 1.8[Formula: see text]V. The transistor counts of the Algorithm-based DNCC are 74 transistors, while they are 106 transistors for the K-map DNCC. The proposed Algorithm-based DNCC saves 32 transistors and approximately reduces its chip area to 69.8% of the K-map DNCC.

Characterization of pre-existing arrhythmogenic substrate associated with de novo early and late postoperative atrial fibrillation

BackgroundPoAF is the most common complication after cardiac surgery and may occur in patients with pre-existing arrhythmogenic substrate. Characterization of this substrate could aid in identifying patients at risk for PoAF. We therefore compared intra-atrial conduction parameters and electrogram morphology between patients without and with early- (≤5 days after surgery) and late- (up to 5 years) postoperative atrial fibrillation (PoAF). Methods and resultsEpicardial mapping of the right and left atrium and Bachmann's Bundle (BB) was performed during sinus rhythm (SR) in 263 patients (207male, 67 ± 11 years). Unipolar potentials were classified as single, short or long double and fractionated potentials. Unipolar voltage, fractionation delay (time difference between the first and last deflection), conduction velocity (CV) and conduction block (CB) prevalence were measured. Comparing patients without (N = 166) and with PoAF (N = 97), PoAF was associated with lower CV and more CB at BB. Unipolar voltages were lower and more low-voltage areas were found at the left and right atrium and BB in PoAF patients. These differences were more pronounced in patients with late-PoAF (6%), which could even occur up to 5 years after surgery. Although several electrophysiological parameters were related to PoAF, age was the only independent predictor. ConclusionsPatients with de novo PoAF have more extensive arrhythmogenic substrate prior to cardiac surgery compared to those who remained in SR, which is even more pronounced in late-PoAF patients. Future studies should evaluate whether intra-operative electrophysiological examination enables identification of patients at risk for developing PoAF and hence (preventive) therapy.

Design and Implementation of Two Hybrid High Frequency DPWMs Using Delay Blocks on FPGAs

The use of very high-resolution digital pulse width modulators (DPWMs) for high frequency dc-dc converters has been steadily increasing in recent years. However, the resolution of the DPWM formed by counters and comparators is limited when the switching frequency rise above MHz range. Given this limitation, new strategies for DPWM architectures are being designed to increase the resolution of the signals. This article proposes two new DPWMs architectures with the aim of increasing the resolution of trigger signals using field programmable gate arrays (FPGAs). The first proposed architecture is a hybrid DPWM, which integrates a clock manager and a delay line. For this architecture, the delay line is configured using FPGA intellectual properties (IP) blocks. This delay stage allows a fine resolution in the picosecond scale. In addition, an alternative solution has been implemented to generate two signals, the main signal and its complementary one, including high resolution for the dead time, which is also configurable. Both architectures have been tested through static and dynamic tests on two FPGAs of different costs, an Artix-7 (low-cost) and a Kintex-UltraScale 7 (high-cost) by Xilinx.

Conduction abnormalities and role of cardiac pacing in cardiac amyloidosis: A systematic review.

Cardiac amyloidosis (CA) is an increasingly recognized cause of heart failure, characterized by extracellular deposition of insoluble protein fibrils leading to progressive myocardial dysfunction. The most common types of cardiac amyloidosis are immunoglobin light-chain (AL) and transthyretin (ATTR). Conduction abnormalities are commonly encountered among patients with cardiac amyloidosis and are an important cause of morbidity and mortality. Abnormalities range from infra-Hisian intraventricular conduction delay and bundle branch block to complete atrioventricular block. Pacemaker placement in CA patients follows established guidelines, similar to those for patients without CA, with generally good efficacy. The role and appropriate timing of pacemakers for primary prevention of brady-arrhythmias in CA remains uncertain. While biventricular (BiV) pacing has been shown to improve clinical outcomes in patients with systolic heart failure without CA, there are few data examining the utility of BiV pacing in patients with CA. With the advent of effective treatments for AL and ATTR, appropriate application of pacing is important to support patients with CA and conduction disease through therapeutic trials. This systematic review summarizes the current literature examining the utility of pacing in CA.