scholarly journals Quantification of Ventricular Repolarization Dispersion Using Digital Processing of the Surface ECG

10.5772/23050 ◽  
2012 ◽  
Author(s):  
Ana Cecilia Vinzio Maggio ◽  
Mara Paula ◽  
Eric Laciar ◽  
Pedro David
Keyword(s):  
Digital Processing ◽  
Ventricular Repolarization ◽  
Surface Ecg

scholarly journals Evaluation of Ventricular Repolarization Parameters in Patients Admitted to Emergency Department with Electrical Injury

2020 ◽  
Keyword(s):  
Ventricular Arrhythmias ◽  
Troponin I ◽  
Ventricular Repolarization ◽  
Control Group ◽  
Qtc Interval ◽  
Elevated Troponin ◽  
Surface Ecg ◽  
Healthy Control ◽  
The Mean ◽  
Electrocardiogram Ecg

Objective: Prolonged T-peak to T-end (Tp-e), a ventricular repolarization parameter, has been related with ventricular arrhythmias (VAs). Novel electrocardiogram (ECG) parameters of ventricular repolarization have received considerable attention recently. In this study, we sought to investigate ventricular repolarization indexes such as the Tp-e and corrected Tp-e (Tp-ec) intervals, Tp-e/QT, Tp-e/QTc, and Tp-ec/QT ratios in patients with electrical injuries (EIs). Methods: Thirty-six patients diagnosed with EIs and 35 age- and sex-matched healthy control patients were included. Admission ECGs of the EI patients were compared with those of the healthy controls. QT and QTc intervals were measured, and the Tp-e and Tp-ec intervals, Tp-e/QT, Tp-ec/QT, and Tp-e/QTc ratios were then calculated from a 12-lead surface ECG. Results: The QT, Tp-e, Tp-e/QT, Tp-e/QTc, Tp-ec/QT were not significantly different between the control group and the EI group (p > 0.05). However, the mean QTc interval was significantly higher in the EI group compared to the control group (412.81 ± 25.46 vs 396.31 ± 26.47 ms; p:0.009). Furthermore, the Tp-ec and Tp-ec/QT of the EI subgroup with elevated troponin levels significantly differed from those of the EI patients with normal troponin levels (p:0.033 and p:0.016, respectively). Conclusions: This retrospective study indicated that patients with EIs tend to have a prolonged QTc interval. Additionally, Tp-ec and Tp-ec/QT, which reportedly designate the tendency for VAs, were significantly higher in the EI patients with elevated troponin I levels than the EI patients with normal troponin levels, suggesting that patients with myocardial injury may be prone to VAs.

scholarly journals T vector velocity: A new ECG biomarker for identifying drug effects on cardiac ventricular repolarization

2018 ◽  
Author(s):  
Werner Bystricky ◽  
Christoph Maier ◽  
Gary Gintant ◽  
Dennis Bergau ◽  
Kent Kamradt ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Drug Effects ◽  
Ventricular Repolarization ◽  
The Body ◽  
Calcium Currents ◽  
Published Data ◽  
Ion Currents ◽  
Vector Velocity ◽  
Surface Ecg ◽  
Auc Value

AbstractWe present a new family TrX of ECG biomarkers based on the T vector velocity (TVV) for assessing drug effects on ventricular repolarization. Assuming a link between the TVV and the instantaneous change of the cellular action potentials, drugs accelerating repolarization by blocking inward (depolarizing) ion currents cause a relative increase of the TVV, while drugs delaying repolarization by blocking outward ion currents cause a relative decrease of the TVV.Evaluating the published data from two FDA funded studies, the TrX effect profiles indicate increasingly delayed electrical activity over the entire repolarization process for drugs solely reducing outward potassium current (dofetilide, moxifloxacin). For drugs eliciting block of the inward sodium or calcium currents (mexiletine, lidocaine), the TrX effect profiles were consistent with accelerated electrical activity in the initial repolarization phase. For multichannel blocking drugs (ranolazine) or drug combinations blocking multiple ion currents (dofetilide + mexiletine, dofetilide + lidocaine), the overall TrX effect profiles indicate a superposition of the individual TrX effect profiles.The parameter Tr40c allows separating pure potassium channel blocking drugs from multichannel blocking drugs with an area under the ROC curve (AUC) value of 0.90, CI = [0.88 to 0.92]. This is significantly larger than the performance of J-Tpeakc (0.81, CI = [0.78 to 0.84]) using the published data from the second FDA study. Further performance improvement was achieved by combining the ten parameters Tr10c to Tr100c in a logistic regression model, resulting in an AUC value of 0.94.The TVV based approach substantially improves assessment of drug effects on cardiac repolarization, providing a plausible and improved mechanistic link between drug effects on ionic currents and overall ventricular repolarization reflected in the body surface ECG. TVV may contribute to a better assessment of the proarrhythmic risk of drugs beyond QTc prolongation and JTpeakc.

Evalualion of ventricular repolarization using surface ECG -comparison between QT,ARI, and QRSTi-

1999 ◽  
Vol 32 ◽  
pp. 49
Author(s):  
Norihiko Ohno ◽  
Hirokazu Saitoh ◽  
Ken-ichi Ogata ◽  
Takuya Ono ◽  
Atsunobu Nomura ◽  
...  
Keyword(s):  
Ventricular Repolarization ◽  
Surface Ecg

scholarly journals The absence of insulin signaling in the heart induces changes in potassium channel expression and ventricular repolarization

2014 ◽  
Vol 306 (5) ◽  
pp. H747-H754 ◽  
Author(s):  
Angelica Lopez-Izquierdo ◽  
Renata O. Pereira ◽  
Adam R. Wende ◽  
Bonnie B. Punske ◽  
E. Dale Abel ◽  
...  
Keyword(s):  
Insulin Signaling ◽  
Insulin Receptors ◽  
Left Ventricular ◽  
Ventricular Repolarization ◽  
Specific Effects ◽  
Surface Ecg ◽  
Channel Expression ◽  
Mrna And Protein Expression ◽  
Impaired Insulin Action ◽  
Animal Models Of Diabetes

Diabetes mellitus increases the risk for cardiac dysfunction, heart failure, and sudden death. The wide array of neurohumoral changes associated with diabetes pose a challenge to understanding the roles of specific pathways that alter cardiac function. Here, we use a mouse model with cardiomyocyte-restricted deletion of insulin receptors (CIRKO, cardiac-specific insulin receptor knockout) to study the specific effects of impaired cardiac insulin signaling on ventricular repolarization, independent of the generalized metabolic derangements associated with diabetes. Impaired insulin action caused a reduction in mRNA and protein expression of several key K+ channels that dominate ventricular repolarization. Specifically, components of transient outward K+ current fast component ( Ito,fast; Kv4.2 and KChiP2) were reduced, consistent with a reduction in the amplitude of Ito,fast in isolated left ventricular CIRKO myocytes, compared with littermate controls. The reduction in Ito,fast resulted in ventricular action potential prolongation and prolongation of the QT interval on the surface ECG. These results support the notion that the lack of insulin signaling in the heart is sufficient to cause the repolarization abnormalities described in other animal models of diabetes.

scholarly journals Correlation of repolarization of ventricular monophasic action potential with ECG in the murine heart

2002 ◽  
Vol 283 (1) ◽  
pp. H372-H381 ◽  
Author(s):  
Stephan Danik ◽  
Candido Cabo ◽  
Christine Chiello ◽  
Sacha Kang ◽  
Andrew L. Wit ◽  
...  
Keyword(s):  
Action Potential ◽  
Cardiac Arrhythmias ◽  
Phenotypic Expression ◽  
Experimental Models ◽  
Ventricular Repolarization ◽  
Membrane Currents ◽  
Monophasic Action Potential ◽  
Surface Ecg ◽  
Potential Map ◽  
Electrocardiogram Ecg

Transgenic mice have become important experimental models in the investigation of mechanisms causing cardiac arrhythmias because of the ability to create strains with alterations in repolarizing membrane currents. It is important to relate alterations in membrane currents in cells to their phenotypic expression on the electrocardiogram (ECG). The murine ECG, however, has unusual characteristics that make interpretation of the phenotypic expression of changes in ventricular repolarization uncertain. The major deflection representing the QRS (referred to as “ a”) is often followed by a secondary slower deflection (“ b”) and sometimes a subtle third deflection (“ c”). To determine whether the second or third deflections or both represent ventricular repolarization, we recorded the ventricular monophasic action potential (MAP) in open-chest mice and correlated repolarization with the ECG. There was no significant correlation by linear regression, between action potential duration to 50% or 90% repolarization (APD50 or APD90), respectively, of the MAP and either the interval from onset of Q to onset of b (Qb interval) or onset of c (Qc interval). Administration of 4-aminopyridine (4-AP) significantly prolonged APD50 and APD90 and the Qb interval, indicating that this deflection on the ECG represents part of ventricular repolarization. After 4-AP, the c wave disappeared, also suggesting that it represents a component of ventricular repolarization. Although it appears that both the b and c waves that follow the Q wave on the ECG represent ventricular repolarization, neither correlates exactly with APD90 of the MAP. Therefore, an accurate measurement of complete repolarization of the murine ventricle cannot be obtained from the surface ECG.

A method to measure pores and fissures in geologic materials under S.E.M. by digital image processing

1978 ◽  
Vol 36 (1) ◽  
pp. 212-213
Author(s):  
L. Montoto ◽  
M. Montoto ◽  
A. Bel-Lan
Keyword(s):  
Image Processing ◽  
Optical Microscopy ◽  
Digital Image Processing ◽  
Digital Image ◽  
Digital Processing ◽  
Free Surfaces ◽  
Geologic Materials ◽  
Automatic Information ◽  
Detector Output ◽  
Rock Specimens

INTRODUCTION.- The physical properties of rock masses are greatly influenced by their internal discontinuities, like pores and fissures. So, these need to be measured as a basis for interpretation. To avoid the basic difficulties of measurement under optical microscopy and analogic image systems, the authors use S.E.M. and multiband digital image processing. In S.E.M., analog signal processing has been used to further image enhancement (1), but automatic information extraction can be achieved by simple digital processing of S.E.M. images (2). The use of multiband image would overcome difficulties such as artifacts introduced by the relative positions of sample and detector or the typicals encountered in optical microscopy.DIGITAL IMAGE PROCESSING.- The studied rock specimens were in the form of flat deformation-free surfaces observed under a Phillips SEM model 500. The SEM detector output signal was recorded in picture form in b&w negatives and digitized using a Perkin Elmer 1010 MP flat microdensitometer.

Digital Processing of STEM Images

1981 ◽  
Vol 39 ◽  
pp. 236-237
Author(s):  
A. V. Crewe ◽  
M. Ohtsuki
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Assembly Language ◽  
Processing System ◽  
Principal Component ◽  
Digital Processing ◽  
Image Analysis System ◽  
Black And White ◽  
Analysis System ◽  
Dose Imaging

We have assembled an image processing system for use with our high resolution STEM for the particular purpose of working with low dose images of biological specimens. The system is quite flexible, however, and can be used for a wide variety of images.The original images are stored on magnetic tape at the microscope using the digitized signals from the detectors. For low dose imaging, these are “first scan” exposures using an automatic montage system. One Nova minicomputer and one tape drive are dedicated to this task.The principal component of the image analysis system is a Lexidata 3400 frame store memory. This memory is arranged in a 640 x 512 x 16 bit configuration. Images are displayed simultaneously on two high resolution monitors, one color and one black and white. Interaction with the memory is obtained using a Nova 4 (32K) computer and a trackball and switch unit provided by Lexidata.The language used is BASIC and uses a variety of assembly language Calls, some provided by Lexidata, but the majority written by students (D. Kopf and N. Townes).

Routine Digital Processing of Microscope Images

1990 ◽  
Vol 48 (1) ◽  
pp. 550-551
Author(s):  
E. Wisse ◽  
A. Geerts ◽  
R.B. De Zanger
Keyword(s):  
Operating System ◽  
Digital Processing ◽  
Hard Disks ◽  
The Sun ◽  
Tape Drive ◽  
High Definition ◽  
Fluorescent Microscope ◽  
Microscope Images ◽  
Helical Scan ◽  
Ethernet Connection

The slowscan and TV signal of the Philips SEM 505 and the signal of a TV camera attached to a Leitz fluorescent microscope, were digitized by the data acquisition processor of a Masscomp 5520S computer, which is based on a 16.7 MHz 68020 CPU with 10 Mb RAM memory, a graphics processor with two frame buffers for images with 8 bit / 256 grey values, a high definition (HD) monitor (910 × 1150), two hard disks (70 and 663 Mb) and a 60 Mb tape drive. The system is equipped with Imaging Technology video digitizing boards: analog I/O, an ALU, and two memory mapped frame buffers for TV images of the IP 512 series. The Masscomp computer has an ethernet connection to other computers, such as a Vax PDP 11/785, and a Sun 368i with a 327 Mb hard disk and a SCSI interface to an Exabyte 2.3 Gb helical scan tape drive. The operating system for these computers is based on different versions of Unix, such as RTU 4.1 (including NFS) on the acquisition computer, bsd 4.3 for the Vax, and Sun OS 4.0.1 for the Sun (with NFS).

Recent Progress and Plans in Computer-Controlled High Resolution Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 154-155
Author(s):  
W.J. de Ruijter ◽  
Peter Rez ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Digital Processing ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Linear Filter ◽  
Contrast Transfer Function ◽  
Image Displacement ◽  
Spatially Resolved ◽  
Wide Range ◽  
On Line

Digital computers are becoming widely recognized as standard accessories for electron microscopy. Due to instrumental innovations the emphasis in digital processing is shifting from off-line manipulation of electron micrographs to on-line image acquisition, analysis and microscope control. An on-line computer leads to better utilization of the instrument and, moreover, the flexibility of software control creates the possibility of a wide range of novel experiments, for example, based on temporal and spatially resolved acquisition of images or microdiffraction patterns. The instrumental resolution in electron microscopy is often restricted by a combination of specimen movement, radiation damage and improper microscope adjustment (where the settings of focus, objective lens stigmatism and especially beam alignment are most critical). We are investigating the possibility of proper microscope alignment based on computer induced tilt of the electron beam. Image details corresponding to specimen spacings larger than ∼20Å are produced mainly through amplitude contrast; an analysis based on geometric optics indicates that beam tilt causes a simple image displacement. Higher resolution detail is characterized by wave propagation through the optical system of the microscope and we find that beam tilt results in a dispersive image displacement, i.e. the displacement varies with spacing. This approach is valid for weak phase objects (such as amorphous thin films), where transfer is simply described by a linear filter (phase contrast transfer function) and for crystalline materials, where imaging is described in terms of dynamical scattering and non-linear imaging theory. In both cases beam tilt introduces image artefacts.

Sign in / Sign up

Export Citation Format

Share Document