FT Method Research Articles

Characterization of an automated method to segment the human locus coeruleus.

Following the development of magnetic resonance imaging (MRI) methods to assay the integrity of catecholamine nuclei, including the locus coeruleus (LC), there has been an effort to develop automated methods that can accurately segment this small structure in an automated manner to promote its widespread use and overcome limitations of manual segmentation. Here we characterize an automated LC segmentation approach (referred to as the funnel-tip [FT] method) in healthy individuals and individuals with LC degeneration in the context of Alzheimer's disease (AD, confirmed with tau-PET imaging using [18F]MK6240). The first sample included n = 190 individuals across the AD spectrum from cognitively normal to moderate AD. LC signal assayed with FT segmentation showed excellent agreement with manual segmentation (intraclass correlation coefficient [ICC] = 0.91). Compared to other methods, the FT method showed numerically higher correlation to AD status (defined by presence of tau: Cohen's d = 0.64) and AD severity (Braak stage: Pearson R = -.35, cognitive function: R = .25). In a separate sample of n = 12 control participants, the FT method showed excellent scan-rescan reliability (ICC = 0.82). In another sample of n = 30 control participants, we found that the structure of the LC defined by FT segmentation approximated its expected shape as a contiguous line: <5% of LC voxels strayed >1 voxel (0.69 mm) from this line. The FT LC segmentation shows high agreement with manual segmentation and captures LC degeneration in AD. This practical method may facilitate larger research studies of the human LC-norepinephrine system and has potential to support future use of neuromelanin-sensitive MRI as a clinical biomarker.

Effects of Chemical Compositions and Cetane Number of Fischer–Tropsch Fuels on Diesel Engine Performance

Fischer–Tropsch synthetic (FT) fuels are expected to be an ideal alternative for diesel fuel to achieve higher thermal efficiency and reduction in exhaust emissions because of their characteristics of being aromatic-free, sulfur-free, and high cetane number. In this study, the effects of chemical compositions and cetane number of FT fuels on diesel engine performance were investigated by using a commercial GTL (Gas-to-Liquids) diesel fuel synthesized by the FT method and blended paraffinic hydrocarbon fuels made to simulate FT fuels with different chemical compositions and cetane numbers. At first, a commercial diesel fuel (JIS No.2) and GTL were examined by varying the intake oxygen concentrations with cooled EGR. Compared with diesel fuel, GTL shows shorter premixed combustion, smaller heat release peak, and longer diffusion combustion duration at both high and medium conditions due to the higher cetane number. Further, by using the GTL, a limited improvement in thermal efficiency and exhaust emission reduction of NOx have been obtained, but no significant reduction in the smoke emissions is achieved, even though FT fuels have been considered smokeless due to their aromatic-free characteristics. Next, three types of paraffinic hydrocarbon fuels with cetane numbers of 78, 57, and 38 were blended as simulated FT fuels and were examined under the same experimental apparatus and operation conditions. For the low cetane number simulated FT fuel (cetane number 38 fuel), the results show that the ignition delay and premixing period are significantly longer at low intake oxygen concentration conditions, meaning that the premixing of low cetane number fuel is more sufficient than other fuels, especially under the high EGR rate conditions, resulting in fewer smoke emissions. Furthermore, with CN38 fuel, an excellent indicated thermal efficiency was obtained at the high load condition. To summarize the results, the low cetane number FT fuel shows a potential to achieve higher thermal efficiency and reduction in exhaust emissions on commercial diesel engines with EGR.

Risk Analysis and Reliability Assessment of Overhead Cranes Using Fault Tree Analysis Integrated with Markov Chain and Fuzzy Bayesian Networks

Establishing an adequate level of reliability in the overhead crane operations is an important and vital principle to avoid undesirable consequences. To do this, it is appropriate to have a comprehensive approach for risk and reliability assessment of the most probable failure scenarios during overhead crane operations. In this study, fault tree analysis (FTA) in combination with fuzzy set theory, Bayesian network (BN), and Markov chain was used to evaluate the probability of top event and reliability of overhead cranes. A total of 47 basic events were identified for ladle fall in overhead cranes. The results showed that the probability of the ladle fall in the FT approach is equal to 0.0523035 and in the BN approach in the prior event is equal to 0.0273394 which is less than the FT method. Based on the values predicted by Markov chain, the reliability of the system decreases over time by 67.9% after 60 months. This study showed that the plan for ladle fall prevention should consider all influencing parameters identified by proper risk assessment methodologies.

Measurement of Free Testosterone in Serum Using Equilibrium DialysisCoupled With ID-UHPLC-MS/MS: Comparison Between Equilibrium Devices

Free testosterone (FT) has been used as a biomarker in clinical patient care and public health research to assess and manage patients with androgenic abnormalities. The latest Endocrine Society clinical practice guideline for testosterone therapy in men with hypogonadism recommends measuring FT for those with borderline and low total testosterone concentrations, or those who have conditions that change SHBG concentrations, such as some metabolic or hormonal diseases, certain medication use, or SHBG genetic polymorphisms. Measuring FT is technically challenging and shows high variability. The CDC clinical standardization program is developing a high throughput method using the gold-standard equilibrium dialysis (ED) procedure with isotope dilution ultra-high-performance liquid chromatography tandem mass spectrometry (ID-UHPLC-MS/MS).A serum sample was dialyzed against a protein-free HEPES buffer (pH 7.4) at 37 °C until equilibrium. After isolating endogenous FT from protein-bound testosterone by ED, isotope-labeled internal standard (13C3-testosterone) was added to the dialysate for quantification. Certified pure primary reference material (National Measurement Institute M914) was used to prepare calibrators, enabling traceable quantitation and ensuring measurement trueness. FT was further isolated from the dialysate matrix using supported liquid extraction and a chromatographic separation from interfering compounds and quantitation by tandem MS. The dialysis step requires maintaining the endogenous free hormone equilibrium so that results in dialysate reflect FT concentrations in the blood without influence from dilution, temperature, or pH. The dialyzer system has a 1:1 sample-to-buffer volume and has been used in reference measurement procedures for free hormone measurements, serving as the standard for method performance comparison. Four commercially available devices designed for high throughput in a multiple well-plate format, requiring respective sample-to-buffer ratios, were evaluated for their recovery, speed, ease of automation by a liquid handling system, repeatability, and robustness. Preliminary results showed that a device with 1:1 sample-to-buffer volume had the most comparable results to those obtained from the standard dialyzer, with the mean bias less than 15%. The device with the highest sample-to-buffer ratio showed bias as high as 50%. These data suggest that controlling sample-to-buffer ratio is a critical step in ED FT method.

EXAFS and XANES study of cobalt complexes synthesized with ligands of chloroaniline and fluoroaniline dithiocarbamate

The cobalt [Co(II)] complexes (03 nos) were synthesized using various ligands of chloroaniline and fluoroaniline dithiocarbamate. The synthesized Co(II) complexes were studied for different physical, structural and chemical parameters using XANES and EXAFS conducted on DXAFS beamline BL-8, Indus 2, Synchrotron source. The EXAFS spectra recorded for Co(II) complexes were used for computation of the bond length, chemical shift, effective nuclear charge, principal absorption maxima and edge width using Athena and Origin 6.0 software. The results of the study revealed that, the synthesized cobalt complexes showed higher value for K-absorption edge (Ek) and Absorption maxima (EA) than Co metal. The Chemical shift (&Delta;EK) value for Co(II) complexes were ranged 1.17-4.52 eV. The Shift of principal absorption maxima (&Delta;EA) value for Co(II) complexes were ranged 0.65-4.18 eV. The Edge width of three different complexes of cobalt [Co(II)] synthesized with ligands of chloroaniline/fluoroaniline dithocarbamate ranged 6.60-11.14 eV. The bond length calculated by LSS method ranged 1.41-2.20 &Aring; for different complexes whereas the bond length calculated by FT method ranged 1.26-3.06 &Aring;. The Lytle&rsquo;s method and Levy&rsquo;s method gives the bond length ranged 2.44-3.08 &Aring; and 1.97-2.58 &Aring;, respectively for studied complexes.

Identification of periodic bursts in surface EMG: Applications to the erector spinae muscles of sitting violin players

ObjectiveThis work compares two known and one novel techniques for the detection of surface EMG (sEMG) quasi-periodic burst-like signals and the estimation of their frequency. The novel method (ES) is based on the spectral analysis of the envelope signal, the other two methods use a fixed (FT) or automatically selected optimal threshold (OT). MethodsThe methods are compared using both simulated signals and samples of High Density sEMG experimental signals collected using electrode arrays applied to the erector spinae muscles of violinists. ResultsThe ES method does not require thresholds. It detects presence/absence of bursts and their frequency, even in cases of a few missing bursts. It does not provide their duration. The FT method requires the selection of a fixed threshold value, estimates burst duration but is applicable only if bursts are present. The OT method identifies an optimal threshold, estimates burst duration but behaves irregularly when bursts are small or absent. ConclusionsThe ES method provides the estimates closest to those of an expert human counter and is not sensitive to amplitude fluctuations. It is suitable when the general bursts periodicity is of interest even if some bursts may be missing. The FT and OT methods are sensitive to amplitude fluctuations and identify random threshold crossings as bursts even when burst activity is absent. SignificancePostural muscles are often activated in a burst-like fashion. The proposed ES method identifies presence/absence of bursts and their frequency, which is important for studying the neurophysiological mechanism generating them.

Efficient and Accurate Frequency-Invariant Beam Pattern Synthesis Utilizing Iterative Spatiotemporal Fourier Transform

An iterative spatiotemporal Fourier transform (STFT) method is presented to efficiently design finite-impulse-response (FIR) filter coefficients for generating a desired frequency-invariant (FI) beam pattern of an antenna array. In this method, by introducing the concepts of normalized temporal angular frequency and spatial angular frequency, the broadband pattern is treated as a spatiotemporal spectral distribution. The relationship between the FIR coefficient distribution and the spatiotemporal spectral distribution can be built as an STFT, and consequently the 2-D fast Fourier transform (2D-FFT) and inverse 2D-FFT (2D-IFFT) can be utilized to efficiently accomplish the transformation between the FIR coefficient distribution and the spatiotemporal spectral distribution. Thus, the proposed synthesis method starts from an initial spatiotemporal spectral distribution and then adopt an iterative modification-and-transformation strategy to successively update the obtained spatiotemporal spectral distribution and the corresponding FIR coefficients. Two kinds of pattern modification techniques including the mainlobe FI modification and broadband sidelobe control are adopted in each iteration. Several examples for synthesizing different FI patterns are conducted. Synthesis results show that the proposed method can obtain much better FI pattern performance in terms of both mainlobe FI property and sidelobe control than the original FT method whilst costing less CPU time than the convex optimization method especially for the case of large FI arrays.

A coarse-to-fine method for glass fiber fabric surface defect detection

Surface defect detection of glass fiber fabrics has always been one of the research hotspots in the field of textile industry. The main reasons are the complexity of defect types, the interference of false defects and the random arrangement of gray values. In this paper, a surface defect detection method for glass fiber fabric based on coarse-to-fine strategy is presented. Firstly, the grayscale values of the images to be detected are arranged in the ascending order by row and column respectively, and the corresponding grayscale value curves are drawn. According to the coordinate defect position obtained by the curve, the defect candidate area of glass fiber fabric image is roughly segmented. Then, the convolution kernel is constructed to convolute the coarse segmented image. Finally, the OTSU algorithm is used to locate defects. Qualitative and quantitative experiments show that the detection results of the proposed method are better than Gabor method, FT method and Zhang’s method. The average detection accuracy of the proposed method can reach 98.8%, which can meet the actual needs of enterprises.

A PREPARAÇÃO DE ELENCO QUE REVOLUCIONOU A INTERPRETAÇÃO DE ATORES NO BRASIL: FÁTIMA TOLEDO E O MÉTODO FT - BASEADO EM ATUAÇÕES REAIS.

Através de uma perspectiva entre a interpretação de atores e as linguagens inseridas no contexto da arte dramática, este artigo expõe a capacidade de opções em instrumentos técnicos e teóricos que o Método Fátima Toledo (também chamado de "Método FT") colabora de maneira positiva e única, pela forma na maioria dos projetos em que a preparação é encontrada, tornando-as peculiares. Com isso, toda a escrita aqui percebida pode desmitificar negatividades em torno do mesmo Método e aparecer como legítima grande aliada de profissionais das artes e de não artistas. No caso dos atores, contribuindo para melhorar suas formas de interpretação. É congruente também para a expansão do Método FT e sua maior valorização sob as artes da cena como um todo, superando a eficácia já demonstrada nos filmes de sucesso no cinema nacional e agora a partir de experiências práticas assumidas pelo escritor. Era essencial apresentar uma relação do Método FT em novos trabalhos, por outro preparador, colocando-os como referência e material de pesquisa. Salienta-se que o uso da ferramenta na interpretação de artistas é cada vez mais importante para o sucesso de um filme. Um dos propósitos é provocar uma reflexão maior sobre a ruptura com pensamentos estereotipados na postura e relação do "ator x personagem".

Comparison of dealiasing schemes in large-eddy simulation of neutrally stratified atmospheric flows

Abstract. Aliasing errors arise in the multiplication of partial sums, such as those encountered when numerically solving the Navier–Stokes equations, and can be detrimental to the accuracy of a numerical solution. In this work, a performance and cost analysis is proposed for widely used dealiasing schemes in large-eddy simulation, focusing on a neutrally stratified, pressure-driven atmospheric boundary-layer flow. Specifically, the exact 3∕2 rule, the Fourier truncation method, and a high-order Fourier smoothing method are intercompared. Tests are performed within a newly developed mixed pseudo-spectral finite differences large-eddy simulation code, parallelized using a two-dimensional pencil decomposition. A series of simulations are performed at varying resolution, and key flow statistics are intercompared among the considered runs and dealiasing schemes. The three dealiasing methods compare well in terms of first- and second-order statistics for the considered cases, with modest local departures that decrease as the grid stencil is reduced. Computed velocity spectra using the 3∕2 rule and the FS method are in good agreement, whereas the FT method yields a spurious energy redistribution across wavenumbers that compromises both the energy-containing and inertial sublayer trends. The main advantage of the FS and FT methods when compared to the 3∕2 rule is a notable reduction in computational cost, with larger savings as the resolution is increased (15 % for a resolution of 1283, up to a theoretical 30 % for a resolution of 20483).

A time-saving method for sealing Purdue Improved Crop Storage (PICS) bags

Purdue Improved Crop Storage (PICS) bags were designed to reduce grain storage losses on smallholder farms. The bag consists of three layers: two high-density polyethylene liners fitted inside a woven polypropylene bag. Recently, farmer groups, development relief programs, and government food security agencies have shown interest in PICS bags for large-scale use. PICS bags are conventionally closed by a twist-tie (TT) method, which involves twisting, folding, and tying the lip of each layer individually with a cord. This is not only time and labor intensive, but also may affect the integrity of the liners. We evaluated three new bag closure methods: i) inner liner rolled onto itself and middle liner fold-tied (IR), ii) both liners folded together and tied (FT), and iii) both liners folded and tied separately (FS), along with the conventional twist tie (TT) method. The time to close partially or fully filled 50 kg-capacity PICS bags filled with maize grain was assessed. Results showed that FT was the most time-saving method, reducing bag sealing time by >34% versus the usual TT method. The average internal oxygen levels reached <2% within a week in bags containing grain highly infested with Sitophilus zeamais, while it remained >5% levels for less-infested bags. In both cases, insect population growth was suppressed. Oxygen depletion rates among tying methods remained the same regardless of the closure method used. When large numbers of bags need to be closed, the time-saving FT method is a good alternative PICS sealing method over the conventional twist-tie approach.

Fourier-Domain Shift Matching: A Robust Time-of-Flight Approach for Shear Wave Speed Estimation.

Our primary objective of this work was to design and test a new time-of-flight (TOF) method that allows measurements of shear wave speed (SWS) following impulsive excitation in soft tissues. Particularly, under the assumption of the local plane shear wave, this work named the Fourier-domain shift matching (FDSM) method, estimates SWS by aligning a series of shear waveforms either temporally or spatially using a solution space deduced by characteristic curves of the well-known 1-D wave equation. The proposed SWS estimation method was tested using computer-simulated data, and tissue-mimicking phantom and ex vivo tissue experiments. Its performance was then compared with three other known TOF methods: lateral time-to-peak (TTP) method with robust random sampling consensus (RANSAC) fitting method, Radon sum transformation method, and a modified cross correlation method. Hereafter, these three TOF methods are referred to as the TTP-RANSAC, Radon sum, and X-corr methods, respectively. In addition to an adapted form of the 2-D Fourier transform (2-D FT)-based method in which the (group) SWS was approximated by averaging phase SWS values was considered for comparison. Based on data evaluated, we found that the overall performance of the above-mentioned temporal implementation of the proposed FDSM method was most similar to the established Radon sum method (correlation = 0.99, scale factor = 1.03, and mean difference = 0.07 m/s), and the 2-D FT (correlation = 0.98, scale factor = 1.00, and mean difference = 0.10 m/s) at high signal quality. However, results obtained from the 2-D FT method diverged (correlation = 0.201) from these of the proposed temporal implementation in the presence of diminished signal quality, whereas the agreement between the Radon sum approach and the proposed temporal implementation largely remained the same (correlation = 0.98).

An effective frame-based high frequency speech transposition by using neural network

This paper investigate design methodology and performance of neural network based frequency transposition algorithm for hearing aid users. High frequency hearing loss associated with hearing disabled person is promising issue for research. Frequency compression and frequency transposition schemes are key solution to overcome high frequency hearing loss. Neural approach to frequency transposition makes algorithm more sensitive, accurate and specific towards processing. The proposed neural network frequency transposition (NNFT) algorithm is based on framing of speech into feature vector for NN with comprehensive training and processing. The parameter to set in NNFT algorithm was calculated by evaluative study. Using these algorithm Marathi alphabets, words, confusing words are efficiently classified. Classification will improve acceptance and rejection rate for FT processing. Validation and testing result of algorithm shows improvement in sensitivity, accuracy, specificity of NNFT method compared to FT method.

Comparative study of experimental and theoretical analysis of EXAFS data of copper complexes using FT method

The X-ray absorption spectra at the K-edge for a series of copper mixed ligand, having hydroxypyridine as one of the ligands, have been investigated in the laboratory X-ray spectroscopic set-up. In the series only X-ray absorption near edge structure (XANES) parameters and bond length using modified Lytle, Levy's and LSS methods were calculated. In the present study the bond lengths are calculated by Fourier Transform method theoretically using IFEFFIT software and compared with experimental results.

A Review on Different Techniques to De-noise a Signal

This work is based on the comparative study of different decomposition methods used to de-noise an ECG signal. There are several signal processing techniques available like Fourier Transform method, Short Term Fourier Transform method, Wavelet analysis, Empirical Mode of Decomposition method etc. Though Fourier Transform method is predominantly used for decomposition purpose but it is not suitable for decomposition of nonstationary signal. However, most of the biomedical signals are non stationary in nature. So the signal should be decently de-noised thus it can provide essential clinical information relevant to patient’s health condition. The difficulties of FT method can be knocked out by Wavelet Transform method. As Wavelet Transform is a non adaptive approach, it is not satisfactory to eliminate the high frequency noise from signal. The complications of WT method can be diminished by Empirical Mode of Decomposition method. A detail study is required to find out the most advantageous decomposition method for an ECG signal.

A phase demodulation method with high spatial resolution for two-dimensional single-shot X-ray Talbot interferometry

A new phase demodulation approach is proposed that uses windowed Fourier transforms to achieve high spatial resolution in fringe pattern analysis with a high signal-to-noise ratio for single-shot X-ray grating-based interferometry. Conventionally, Fourier transforms have been used to demodulate single-fringe patterns, but this requires a fringe pattern with a long period to obtain an acceptable signal-to-noise ratio among the demodulated parameters. However, by controlling the signal-to-noise ratio, the spatial resolution of demodulated parameters is degraded below that obtained from the phase-stepping method, which requires several images to obtain these parameters. In this paper, we introduce the use of a windowed Fourier transform with a process for analyzing the objective spectrum in isolation from other spectra on the Fourier space to overcome the limitations of the Fourier transform method. It is proved that with suitable assumptions the objective spectrum is isolated theoretically, and the spatial resolution is improved by practically accepting the limitations from the assumptions. We demonstrate the validity of the proposed method by comparing the modulation transfer function of a synthetic phantom with the conventional FT method. The proposed method is also valid on practical data obtained by an experimental setup, by which it is demonstrated that a high spatial resolution with high signal-to-noise ratio can be achieved by our proposed method.

Evaluation of development in indirect determination of milk fat free fatty acids in Czech Republic

Free fatty acids (FFAs) in fat are important indicator of raw milk quality. Result reliability of FFAs is important. Aim was to verify MIR–FT (mid infrared spectroscopy with Fourier’s transformations) method for its calibration to determine FFAs, time stability of MIR–FT FFA calibration and calibration levelling in laboratory networks. Reference (RE) milk samples (1 set = 8) were prepared according to CSN 57 0533 (FFAs in mmol.100g−1 of fat). MIR–FT instruments were: 1 LactoScope FTIR (DE); 2 Bentley FTS (BE); 2 MilkoScan FT 6000 (FO). 3 calibrations of MIR–FT (5) in 3 laboratories were performed. Bulk milk samples came from 4 herds and 2 breeds. These 4 samples were used for calibration in native and modified form. Modification increased FFAs by cca 100%. Calibration set had 8 samples. 1 between calibration interval was checked monthly by proficiency testing (PT). PT set had 10 samples. 5 samples were with native milk and 5 had modified fat content, lower and higher. Maximal value of difference variability for calibration quality validation is x (sd of difference MIR–FT and RE) plus 1.64 multiple of sd (on 95% level), 1.0613 mmol.100g−1. Mean validation correlation coefficient (r) between MIR–FT and RE results was 0.802 ± 0.082 (P &lt; 0.001), from 0.666 to 0.945. Minimal value at calibration is x minus 1.64 multiple of sd (0.668). Correlations between MIR–FT results were higher by 8.4% (0.869 (P &lt; 0.001) &gt; 0.802). Example PT with 10 and 5 milk samples had similar results of r 0.887 and 0.953 (P &lt; 0.001 and P &lt; 0.05). There is possibility to construct a levelling programme for calibrated instruments. Some equation between PT reference and instrumental values could correct MIR–FT results for their better comparability.

101 VALIDATION OF MAGNETIC RESONANCE FEATURE TRACKING FOR LONGITUDINAL SYSTOLIC AND DIASTOLIC STRAIN CALCULATION WITH SPATIAL MODULATION OF MAGNETISATION IMAGING ANALYSIS

IntroductionFeature-tracking (FT) analysis offers a novel, fast and practicable method to calculate strain from routinely acquired steady state free precession (SSFP) images without the need to perform additional tagged sequences....

Validating feature tracking MRI for the assessment of strain rate in patients with various hemodyanamic states

Background Myocardial strain rate (SR) is a valuable measurement in assessing myocardial mechanical properties, which can be compared between subjects in the setting of various hemodynamic states. Featur et racking (FT) is an ovel method to assess SR off-line on cine images acquired in routine cardiac MRI. In this study we sought to assess SR using the FT method in a group of patients and to validate the relation of SR to LV ejection fraction (LVEF) and left ventricular end diastolic pressure (LVEDP) measured during cardiac catheterization. Methods Mean age of the cohort was 59 years with 32 patients being male (61%). The average LVEF was 49±15%, LVEDV 90±38 mL/m2 and LVEDP 14±7 mmHg. The average circumferential SR was higher in patients with a normal LVEF (≥50%) -1.6±0.4s-1 versus patients with a low LVEF (<50%) -0.7±0.4s-1 (p<0.001). Significant dif- ferences were also noted in average radial SR in patients with normal LVEF 2.1±0.8s-1 versus 0.9±0.5</s-1 (p<0.001) in patients with a low LVEF. While average strain rates were consistently higher in patients with a normal LVEF, there is a lack of linear correlation between circumferential SR and radial SR with LVEF (p=0.241 and 0.987, respectively). In contrast, among patients with low LVEF, the correlation was excellent with r=0.810 (p<0.001) for circumferential SR and r=0.730 (p=0.002) for radial SR. In univariate analysis LVEDP significantly correlated with circumferential SR and radial SR (r=0.579, p<0.001 and r=-0.438, p=0.001, respectively). However, in am ultivariate regression model including LVEDP, LVEF, LVEDV, and LVESV as covariables to assess their relationship to circumferential SR and radial SR, LVEDP was not significantly asso- ciated with either SR measurements while LVESV and LVEF were significantly associated with circumferential SR and radial SR. Conclusions FT-MRI is a promising method to assess SR in off-line standard cine images. SR assessed by FT is sensitive to change in global LV dysfunction yet independent of LV preload condition. Funding None.

Utility and Validation of Corrected Left Ventricular Filling Time for Determining the Optimal AV Delay in Patients Receiving Cardiac Resynchronization Therapy

Background: Optimizing the atrio-ventricular delay (AVD) is important for increasing the left ventricular (LV) preload in patients receiving cardiac resynchronization therapy (CRT). The optimal AVD may be considered an AVD in which the maximum LV filling time (LVFT) is obtained. However, it is unclear whether or not the optimal AVD determined by Ritter's method (AVD-Ritter) is identical to the AVD in which the maximum LVFT is obtained. The aim of this study was to clarify this point.Methods: In 17 patients who received CRT, the optimal AVD was determined by Ritter's method and the FT method. Eleven (65%) patients had 1° AV block. We measured the LVFT and R-R time when the AVD was prolonged by 20 ms increments from 80 ms to 180 ms. In the FT method, the optimal AVD (AVD-FT) was defined as the AVD in which the corrected LVFT (LVFTc) was maximally prolonged. The AVD-Ritter and AVD-FT were both determined during atrial pacing (Ap) and sensing (As). The LVFTc at each optimal AVD was also measured and compared.Results: During As, the AVD-Ritter (114 ± 20 ms) showed a marginally significant difference when compared to the AVD-FT (95 ± 18 ms; p = 0.053). However, during Ap, the AVD-Ritter (138 ± 32 ms) was significantly longer than the AVD-ET (113 ± 20 ms; p = 0.017). The LVFTc with the AVD-Ritter was shorter than the AVD-FT (As: 538 ± 40 vs. 557 ± 34 [ms], p = 0.002; Ap: 532 ± 37 vs. 563 ± 33 [ms], p = 0.023). These results were comparable with those obtained in the 11 patients with 1° AV block.Conclusions: The AVD-Ritter during Ap may become shorter than that for the AVD-FT because of the latency in patients receiving CRT. The FT method might be better than the AVD-Ritter method to optimize the AVD in those patients.