scholarly journals Role of KATP channel in electrical depression and asystole during long-duration ventricular fibrillation in ex vivo canine heart

2012 ◽  
Vol 302 (11) ◽  
pp. H2396-H2409 ◽  
Author(s):  
Tyson G. Taylor ◽  
Paul W. Venable ◽  
Junko Shibayama ◽  
Mark Warren ◽  
Alexey V. Zaitsev
Keyword(s):  
Ventricular Fibrillation ◽  
Ex Vivo ◽  
Atrial Pacing ◽  
Canine Heart ◽  
Long Duration ◽  
Myocardial Layers ◽  
The Difference ◽  
Prolonged Action Potential Duration ◽  
Unipolar Electrograms

Long-duration ventricular fibrillation (LDVF) in the globally ischemic heart is characterized by transmurally heterogeneous decline in ventricular fibrillation rate (VFR), emergence of inexcitable regions, and eventual global asystole. Rapid loss of both local and global excitability is detrimental to successful defibrillation and resuscitation during cardiac arrest. We sought to assess the role of the ATP-sensitive potassium current ( IKATP) in the timing and spatial pattern of electrical depression during LDVF in a structurally normal canine heart. We analyzed endo-, mid-, and epicardial unipolar electrograms and epicardial optical recordings in the left ventricle of isolated canine hearts during 10 min of LDVF in the absence (control) and presence of an IKATP blocker glybenclamide (60 μM). In all myocardial layers, average VFR was the same or higher in glybenclamide-treated than in control hearts. The difference increased with time of LDVF and was overall significant in all layers ( P < 0.05). However, glybenclamide did not significantly affect the transmural VFR gradient. In epicardial optical recordings, glybenclamide shortened diastolic intervals, prolonged action potential duration, and decreased the percentage of inexcitable area (all differences P < 0.001). During 10 min of LDVF, asystole occurred in 55.6% of control and none of glybenclamide-treated hearts ( P < 0.05). In three hearts paced after the onset of asystole, there was no response to LV epicardial or atrial pacing. In structurally normal canine hearts, IKATP opening during LDVF is a major factor in the onset of local and global inexcitability, whereas it has a limited role in overall deceleration of VFR and the transmural VFR gradient.

scholarly journals Quantitative Evaluation of Human Lens Epithelial Cell Viability and Cytolysis by Distilled Water Ex Vivo

2021 ◽  
Author(s):  
Wen-Wen Zhang ◽  
Rong-Pei Zhang ◽  
Ya-Jun Liu ◽  
Zi-Fang He ◽  
Si Zhang ◽  
...  
Keyword(s):  
Cell Viability ◽  
Ex Vivo ◽  
Lens Epithelial Cell ◽  
Human Lens ◽  
Distilled Water ◽  
Histopathological Changes ◽  
Human Lens Epithelial Cell ◽  
Transmission Electron ◽  
The Difference

Abstract Purpose: To investigate the role of distilled water (DW) in isolated human lens epithelial cells (LECs) viability and lysis ex vivo.Methods: After immersion in DW or balanced salt solution (BSS) for 1-, 2-, and 3-minutes, respectively, the cell viability of LECs was quantitatively evaluated. In addition, the capsule samples soaked in DW or BSS for 1-, 2-, and 3-minutes were combined with rinse for 1 minute to analyze the difference of LECs shedding percentage in each subgroup. The histopathological changes of the samples after treating were observed.Results: The percentage of LECs shed in DW immersion combined with rinse was significantly higher than in DW immersion alone (p all <0.001). In the subgroup soaked in DW for 3 minutes, the death number, mortality, and the percentage of cell shedding of LECs was the most (p all <0.001). The histopathological changes showed that the cell destruction in the DW subgroup for 1-, 2-, and 3-minutes, and the transmission electron microscope results showed that the cells were partially detached from the capsule in the DW 3 minutes subgroup.Conclusions: Soaking in the DW can cause LECs death, and DW immersion combined with rinse was an effective method to remove LECs. The histopathology changes of treated DW suggested cellular necrosis was one type of LECs death mechanism.

scholarly journals Activation becomes highly organized during long-duration ventricular fibrillation in canine hearts

2010 ◽  
Vol 298 (6) ◽  
pp. H2046-H2053 ◽  
Author(s):  
Li Li ◽  
Qi Jin ◽  
Derek J. Dosdall ◽  
Jian Huang ◽  
Steven M. Pogwizd ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Conduction Block ◽  
Three Dimensional ◽  
Left Ventricular ◽  
The Body ◽  
Long Duration ◽  
Surface Ecg ◽  
Electrode Matrix ◽  
Different Levels

Little is known about the three-dimensional (3-D) intramural activation sequences during long-duration ventricular fibrillation (VF), including the role of the subendocardium and its Purkinje fibers (PFs) in long-duration VF maintenance. Our aim was to explore the mechanism of long-duration VF maintenance with 3-D electrical mapping. We recorded 10 min of electrically induced VF in the left ventricular anterior free wall of six 10-kg, open-chest dogs using a 3-D transmural unipolar electrode matrix (9 × 9 × 6, 2-mm spacing) that allowed us to map intramural activation sequences. At 2.5 ± 1.8 min of VF, although the body surface ECG continued to exhibit a disorganized VF pattern, intramurally a more organized, synchronous activation pattern was first observed [locally synchronized VF (LSVF)]. This pattern occurred one or more times in all dogs and was present 33.4 ± 31.4% of the time during 5–10 min of VF. As opposed to the preceding changing complex activation sequences of VF, during LSVF, wavefronts were large and highly repeatable near the endocardium, first exciting the endocardium almost simultaneously and then rapidly spreading toward the epicardium with different levels of conduction block en route. During LSVF, PF activations always preceded working myocardium activations near the endocardium. In conclusion, long-duration VF in dogs frequently becomes highly organized in the subendocardium, with activation fronts arising in this region and passing intramurally toward the epicardium, even though the surface ECG continues to exhibit a disorganized pattern. PFs appear to play an important role during this stage of VF.

scholarly journals Verapamil reduces incidence of reentry during ventricular fibrillation in pigs

2014 ◽  
Vol 307 (9) ◽  
pp. H1361-H1369 ◽  
Author(s):  
Qi Jin ◽  
Derek J. Dosdall ◽  
Li Li ◽  
Jack M. Rogers ◽  
Raymond E. Ideker ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Conduction Velocity ◽  
Cycle Length ◽  
Conduction Block ◽  
Antiarrhythmic Effect ◽  
Delayed Rectifier ◽  
Activation Patterns ◽  
Long Duration ◽  
Activation Rate

The characteristics of reentrant circuits during short duration ventricular fibrillation (SDVF; 20 s in duration) and the role of Ca++ and rapid-activating delayed rectifier potassium currents during long duration ventricular fibrillation (LDVF; up to 10 min in duration) were investigated using verapamil and sotalol. Activation mapping of the LV epicardium with a 21 × 24 electrode plaque was performed in 12 open-chest pigs. Pigs were given either verapamil (0.136 mg/kg) or sotalol (1.5 mg/kg) and verapamil. Reentry patterns were quantified for SDVF, and, for LDVF, activation patterns were compared with our previously reported control LDVF data. Verapamil significantly increased conduction velocity around the reentrant core by 10% and reduced the reentrant cycle length by 15%, with a net reduction in reentry incidence of 70%. Sotolol had an opposite effect of decreasing the conduction velocity around the core by 6% but increasing the reentrant cycle length by 13%, with a net reduction of reentry incidence of 50%. After 200 s of VF, verapamil significantly slowed wavefront conduction velocity and activation rate compared with control data. Verapamil decreased the incidence of reentry in SDVF by accelerating conduction velocity to increase the likelihood of conduction block, possibly through increased sympathetic tone. The drug slowed activation rate and conduction velocity after 200 s of VF, suggesting that L-type Ca++ channels remain active and may be important in the maintenance of LDVF. Sotalol in addition to verapamil caused no additional antiarrhythmic effect.

scholarly journals Complex structure of electrophysiological gradients emerging during long-duration ventricular fibrillation in the canine heart

2010 ◽  
Vol 299 (5) ◽  
pp. H1405-H1418 ◽  
Author(s):  
Paul W. Venable ◽  
Tyson G. Taylor ◽  
Junko Shibayama ◽  
Mark Warren ◽  
Alexey V. Zaitsev
Keyword(s):  
Ventricular Fibrillation ◽  
Optical Mapping ◽  
Complex Structure ◽  
Canine Heart ◽  
Purkinje Fibers ◽  
Isolated Hearts ◽  
Long Duration ◽  
Activation Rate ◽  
Highly Correlated ◽  
The Right

Long-duration ventricular fibrillation (LDVF) in the globally ischemic heart is a common setting of cardiac arrest. Electrical heterogeneities during LDVF may affect outcomes of defibrillation and resuscitation. Previous studies in large mammalian hearts have investigated the role of Purkinje fibers and electrophysiological gradients between the endocardium (Endo) and epicardium (Epi). Much less is known about gradients between the right ventricle (RV) and left ventricle (LV) and within each chamber during LDVF. We studied the transmural distribution of the VF activation rate (VFR) in the RV and LV and at the junction of RV, LV, and septum (Sep) during LDVF using plunge needle electrodes in opened-chest dogs. We also used optical mapping to analyze the Epi distribution of VFR, action potential duration (APD), and diastolic interval (DI) during LDVF in the RV and LV of isolated hearts. Transmural VFR gradients developed in both the RV and LV, with a faster VFR in Endo. Concurrently, large VFR gradients developed in Epi, with the fastest VFR in the RV-Sep junction, intermediate in the RV, and slowest in the LV. Optical mapping revealed a progressively increasing VFR dispersion within both the LV and RV, with a mosaic presence of fully inexcitable areas after 4–8 min of LDVF. The transmural, interchamber, and intrachamber VFR heterogeneities were of similar magnitude. In both chambers, the inverse of VFR was highly correlated with DI, but not APD, at all time points of LDVF. We conclude that the complex VFR gradients during LDVF in the canine heart cannot be explained solely by the distribution of Purkinje fibers and are related to regional differences in the electrical depression secondary to LDVF.

scholarly journals Activation Patterns of Purkinje Fibers During Long-Duration Ventricular Fibrillation in an Isolated Canine Heart Model

Circulation ◽  
2007 ◽  
Vol 116 (10) ◽  
pp. 1113-1119 ◽  
Author(s):  
Paul B. Tabereaux ◽  
Greg P. Walcott ◽  
Jack M. Rogers ◽  
Jong Kim ◽  
Derek J. Dosdall ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Canine Heart ◽  
Heart Model ◽  
Activation Patterns ◽  
Purkinje Fibers ◽  
Long Duration

scholarly journals The role of marshall bundle epicardial connections in atrial tachycardias after atrial fibrillation ablation

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
K Vlachos ◽  
A Denis ◽  
T Kitamura ◽  
M Takigawa ◽  
A Frontera ◽  
...  
Keyword(s):  
Pulmonary Veins ◽  
Mitral Annulus ◽  
Af Ablation ◽  
Funding Sources ◽  
Ethanol Infusion ◽  
Long Duration ◽  
Lateral Ridge ◽  
The Difference

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial tachycardias (ATs) are often seen in the context of AF ablation. Objectives We evaluated the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density high-spatial resolution 3D mapping. Methods 199 post-AF ablation LA tachycardias were mapped in 140 consecutive patients (112 (80%) males, mean age: 61.8 years); 133 (66.8%) were macro-reentrant and 66 (33.2%) were scar-related re-entry. MB-dependent perimitral AT (PMAT) was diagnosed where the difference between the post pacing interval and the tachycardia cycle length (PPI-TCL) was &lt;20ms in parts of the expected MB-dependent perimitral circuit (within the VOM, the ridge between the left pulmonary veins and LA appendage (LAA), the anterior LA and between 6- and 11-o’clock of the mitral annulus) and the PPI-TCL was &gt;20ms in areas bypassed by the VOM (the distal coronary sinus (CS), the posterior LA and the mitral isthmus). MB-related re-entry was diagnosed by PPI-TCL &lt;20ms at the left lateral ridge, posterior base of LAA, inferolateral LA or VOM ostium; and PPI-TCL &gt;20ms in the septal annulus. Typically, in MB-dependent localized re-entry, the earliest activation was found along the MB-LA endocardial connection or MB-CS epicardial connection.  Results The MB network was found to participate in 60 (30.2%) re-entrant ATs, 31 PMATs and 29 localized re-entries. High-frequency multiphasic fragmented electrograms with long duration were often recorded endocardially or epicardially at the MB-LA or MB-CS connections. The amplitude and duration of these signals were 0.5 ± 0.79 mV and 65 ± 40 ms for MB-PMATs and 0.26 ± 0.28mV and 122 ± 67 ms for MB-localized re-entries. Unipolar EGMs at the site of endocardial-epicardial breakthrough had a rS pattern in all MB-related ATs. Of 60 MB-related ATs, 49 (81.6%) terminated with RF ablation, 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-CS junction, while 9 (15%) terminated after 2.5-5 cc of alcohol infusion inside the vein of Marshall (VOM). Of the 31 MB-related macroreentrant ATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction and 7 (22.6%) with alcohol infusion inside the VOM. Two macroreentries (6.5%) using the MB did not terminate with RF energy either endocardially at the MB-LA junction or epicardially at the MB-CS junction, and we were unable to identify or cannulate the VOM for ethanol infusion. Of the 29 localized re-entrant ATs using the MB, 27 (93.1%) terminated at the MB-LA junction, none terminated at the MB-CS junction and 2 (6.9%) terminated after alcohol infusion. After a mean follow up of 12 months, only 4 patients (6.7%) had AT recurrence. Conclusions MB re-entrant ATs accounted for up to 29% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or alcohol infusion inside the VOM is required to treat these arrhythmias. Abstract Figure.

The role of differential phase contrast in electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 176-177
Author(s):  
E.M. Waddell ◽  
J.N. Chapman ◽  
R.P. Ferrier
Keyword(s):  
Phase Contrast ◽  
Practical Method ◽  
Position Vector ◽  
Differential Phase ◽  
Pure Phase ◽  
Differential Phase Contrast ◽  
The Difference ◽  
Image Position ◽  
First Moment

Dekkers and de Lang (1977) have discussed a practical method of realising differential phase contrast in a STEM. The method involves taking the difference signal from two semi-circular detectors placed symmetrically about the optic axis and subtending the same angle (2α) at the specimen as that of the cone of illumination. Such a system, or an obvious generalisation of it, namely a quadrant detector, has the characteristic of responding to the gradient of the phase of the specimen transmittance. In this paper we shall compare the performance of this type of system with that of a first moment detector (Waddell et al.1977).For a first moment detector the response function R(k) is of the form R(k) = ck where c is a constant, k is a position vector in the detector plane and the vector nature of R(k)indicates that two signals are produced. This type of system would produce an image signal given bywhere the specimen transmittance is given by a (r) exp (iϕ (r), r is a position vector in object space, ro the position of the probe, ⊛ represents a convolution integral and it has been assumed that we have a coherent probe, with a complex disturbance of the form b(r-ro) exp (iζ (r-ro)). Thus the image signal for a pure phase object imaged in a STEM using a first moment detector is b2 ⊛ ▽ø. Note that this puts no restrictions on the magnitude of the variation of the phase function, but does assume an infinite detector.

The Shikani HME: A New Tracheostomy Heat and Moisture Exchanger

2020 ◽  
Vol 63 (9) ◽  
pp. 2921-2929
Author(s):  
Alan H. Shikani ◽  
Elamin M. Elamin ◽  
Andrew C. Miller
Keyword(s):  
Ex Vivo ◽  
Moisture Loss ◽  
Speaking Valve ◽  
Time Zero ◽  
In Series ◽  
Turbulent Airflow ◽  
The Difference ◽  
Loss Efficiency ◽  
Heat And Moisture ◽  
Lung Simulation

Purpose Tracheostomy patients face many adversities including loss of phonation and essential airway functions including air filtering, warming, and humidification. Heat and moisture exchangers (HMEs) facilitate humidification and filtering of inspired air. The Shikani HME (S-HME) is a novel turbulent airflow HME that may be used in-line with the Shikani Speaking Valve (SSV), allowing for uniquely preserved phonation during humidification. The aims of this study were to (a) compare the airflow resistance ( R airflow ) and humidification efficiency of the S-HME and the Mallinckrodt Tracheolife II tracheostomy HME (M-HME) when dry (time zero) and wet (after 24 hr) and (b) determine if in-line application of the S-HME with a tracheostomy speaking valve significantly increases R airflow over a tracheostomy speaking valve alone (whether SSV or Passy Muir Valve [PMV]). Method A prospective observational ex vivo study was conducted using a pneumotachometer lung simulation unit to measure airflow ( Q ) amplitude and R airflow , as indicated by a pressure drop ( P Drop ) across the device (S-HME, M-HME, SSV + S-HME, and PMV). Additionally, P Drop was studied for the S-HME and M-HME when dry at time zero (T 0 ) and after 24 hr of moisture testing (T 24 ) at Q of 0.5, 1, and 1.5 L/s. Results R airflow was significantly less for the S-HME than M-HME (T 0 and T 24 ). R airflow of the SSV + S-HME in series did not significant increase R airflow over the SSV or PMV alone. Moisture loss efficiency trended toward greater efficiency for the S-HME; however, the difference was not statistically significant. Conclusions The turbulent flow S-HME provides heat and moisture exchange with similar or greater efficacy than the widely used laminar airflow M-HME, but with significantly lower resistance. The S-HME also allows the innovative advantage of in-line use with the SSV, hence allowing concurrent humidification and phonation during application, without having to manipulate either device.

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