scholarly journals Calcium signals recorded from cut frog twitch fibers containing antipyrylazo III.

1987 ◽  
Vol 89 (1) ◽  
pp. 83-143 ◽  
Author(s):  
J Maylie ◽  
M Irving ◽  
N L Sizto ◽  
W K Chandler
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Time Course ◽  
Wavelength Dependence ◽  
Difference Spectrum ◽  
Half Width ◽  
Arsenazo Iii ◽  
Transverse Tubular System ◽  
Low Amplitude ◽  
Regulatory Sites

The Ca indicator antipyrylazo III was introduced into cut frog twitch fibers by diffusion (Maylie, J., M. Irving, N. L. Sizto, and W. K. Chandler. 1987. Journal of General Physiology. 89:41-81). Like arsenazo III, antipyrylazo III was largely bound to or sequestered by intracellular constituents; on average, a fraction 0.68 was so immobilized. After action potential stimulation, there was an early change in absorbance, with a wavelength dependence that nearly matched a cuvette Ca-difference spectrum. As with arsenazo III, this signal became prolonged as experiments progressed. In a freshly prepared cut fiber containing 0.3 mM indicator, the absorbance change had an average half-width of 10 ms at 18 degrees C. The peak amplitude of this Ca signal depended on the indicator concentration in a roughly parabolic manner, which is consistent with a 1:2 stoichiometry for Ca:indicator complexation and, for indicator concentrations less than or equal to 0.4 mM, constant peak free [Ca]. If all the antipyrylazo III inside a fiber can react normally with Ca, peak free [Ca] is 3 microM at 18 degrees C. If only freely diffusible indicator can react, the estimate is 42 microM. The true amplitude probably lies somewhere in between. The time course of Ca binding to intracellular buffers and of Ca release from the sarcoplasmic reticulum is estimated from the 3- and 42-microM myoplasmic [Ca] transients. After action potential stimulation, the release waveform is rapid and brief; its latency after the surface action potential is 2-3 ms and its half-width is 2-4 ms. This requires rapid coupling between the action potential in the transverse tubular system and Ca release from the sarcoplasmic reticulum. The peak fractional occupancy calculated for Ca-regulatory sites on troponin is 0.46 for the 3-microM transient and 0.93 for the 42-microM transient. During a 100-ms tetanus at 100 Hz, the corresponding fractional occupancies are 0.56 and 0.94. The low value of occupancy associated with the low-amplitude [Ca] calibration seems inconsistent with a brief tetanus being able to produce near-maximal activation (Blinks, J. R., R. Rudel, and S. R. Taylor. 1978. Journal of Physiology. 277:291-323; Lopez J. R., L. A. Wanck, and S. R. Taylor. 1981. Science. 214:47-82).

scholarly journals Calcium signals recorded from cut frog twitch fibers containing tetramethylmurexide.

1987 ◽  
Vol 89 (1) ◽  
pp. 145-176 ◽  
Author(s):  
J Maylie ◽  
M Irving ◽  
N L Sizto ◽  
G Boyarsky ◽  
W K Chandler
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Time Course ◽  
Diffusion Constant ◽  
Wavelength Dependence ◽  
Difference Spectrum ◽  
Optical Recording ◽  
Absorbance Spectrum ◽  
Transient Change ◽  
Early Peak ◽  
Average Rise

The Ca indicator tetramethylmurexide was introduced into cut fibers, mounted in a double-Vaseline-gap chamber, by diffusion from the end-pool solutions. The indicator diffused rapidly to the central region of a fiber where optical recording was done and, if removed, diffused away equally fast. The time course of concentration suggests that, on average, a fraction 0.27 of indicator was reversibly bound to myoplasmic constituents and the free diffusion constant was 1.75 x 10(-6) cm2/s at 18 degrees C. The shape of the resting absorbance spectrum suggests that a fraction 0.11-0.15 of tetramethylmurexide inside a fiber was complexed with Ca. After action potential stimulation, there was a rapid transient change in indicator absorbance followed by a maintained change of opposite sign. The wavelength dependence of both changes matched a cuvette Ca-difference spectrum. The amplitude of the early peak varied linearly with indicator concentration and corresponded to an average rise in free [Ca] of 17 microM. These rather diverse findings can be explained if the sarcoplasmic reticulum membranes are permeable to Ca-free indicator. Both Ca-free and Ca-complexed indicator inside the sarcoplasmic reticulum would appear to be bound by diffusion analysis and the Ca-complexed form would be detected by the resting absorbance spectrum. The transient change in indicator absorbance would be produced by myoplasmic Ca reacting with indicator molecules that freely diffuse in myoplasmic solution. The maintained signal, which reports Ca dissociating from indicator complexed at rest, would come from changes within the sarcoplasmic reticulum. A method, based on these ideas, is described for separating the two components of the tetramethylmurexide signal. The estimated myoplasmic free [Ca] transient has an average peak value of 26 microM at 18 degrees C. Its time course is similar to, but possibly faster than, that recorded with antipyrylazo III (Maylie, J., M. Irving, N. L. Sizto, and W. K. Chandler. 1987. Journal of General Physiology. 89:83-143).

scholarly journals Comparison of arsenazo III optical signals in intact and cut frog twitch fibers.

1987 ◽  
Vol 89 (1) ◽  
pp. 41-81 ◽  
Author(s):  
J Maylie ◽  
M Irving ◽  
N L Sizto ◽  
W K Chandler
Keyword(s):  
Action Potential ◽  
Time Course ◽  
Physiological State ◽  
Diffusion Constant ◽  
Wavelength Dependence ◽  
Optical Recording ◽  
Arsenazo Iii ◽  
Optical Signals ◽  
Indicator Concentration ◽  
Electrical Condition

The Ca indicator arsenazo III was introduced into cut frog twitch fibers by diffusion from end-pool segments rendered permeable by saponin. After 2-3 h, the arsenazo III concentration at the optical recording site in the center of a fiber reached two to three times that in the end-pool solutions. Thus, arsenazo III was bound to or taken up by intracellular constituents. The time course of indicator appearance was fitted by equations for diffusion plus linear reversible binding; on average, 0.73 of the indicator was bound and the free diffusion constant was 0.86 x 10(-6) cm2/s at 18 degrees C. When the indicator was removed from the end pools, it failed to diffuse away from the optical site as rapidly as it had diffused in. The wavelength dependence of resting arsenazo III absorbance was the same in cut fibers and injected intact fibers. After action potential stimulation, the active Ca and dichroic signals were similar in the two preparations, which indicates that arsenazo III undergoes the same changes in absorbance and orientation in both cut and intact fibers. Ca transients in freshly prepared cut fibers appeared to be similar to those in intact fibers. As a cut fiber experiment progressed, however, the Ca signal changed. With action potential stimulation, the half-width of the signal gradually increased, regardless of whether the indicator concentration was increasing or decreasing. This increase was usually not accompanied by any change in the amplitude of the Ca signal at a given indicator concentration or by any obvious deterioration in the electrical condition of the fiber. In voltage-clamp experiments near threshold, the relation between peak [Ca] and voltage usually became less steep with time and shifted to more negative potentials. All these changes were also observed in cut fibers containing antipyrylazo III (Maylie, J., M. Irving, N. L. Sizto, and W. K. Chandler. 1987. Journal of General Physiology. 89:83-143). They are considered to represent a progressive change in the physiological state of a cut fiber during the time course of an experiment.

scholarly journals Calcium signals recorded from two new purpurate indicators inside frog cut twitch fibers.

1989 ◽  
Vol 94 (4) ◽  
pp. 597-631 ◽  
Author(s):  
A Hirota ◽  
W K Chandler ◽  
P L Southwick ◽  
A S Waggoner
Keyword(s):  
Action Potential ◽  
Time Course ◽  
Wavelength Dependence ◽  
Difference Spectrum ◽  
Reliable Estimate ◽  
Spatial Average ◽  
Diacetic Acid ◽  
Absorbance Spectrum ◽  
Average Amplitude ◽  
Apparent Dissociation Constant

Two new Ca indicators, purpurate-3,3'diacetic acid (PDAA) and 1,1'-dimethylpurpurate-3,3'diacetic acid (DMPDAA), were synthesized and used to measure Ca transients in frog cut muscle fibers. These indicators are analogues of the purpurate components of murexide and tetramethylmurexide, in which two acetate groups have been incorporated into each molecule to render it membrane impermeant. The apparent dissociation constant for Ca is 0.95 mM for PDAA and 0.78 mM for DMPDAA. One of the indicators was introduced into a cut fiber, which was mounted in a double Vaseline-gap chamber, by diffusion from the end-pool solutions. The time course of indicator concentration, monitored optically in the middle of the fiber in the central-pool region, suggests that 19% of the PDAA or 27% of the DMPDAA became bound or sequestered inside the fiber. In resting fibers, the absorbance spectrum of either indicator was well fitted by the indicator's [Ca] = 0 mM cuvette absorbance spectrum, which is consistent with the idea that PDAA and DMPDAA do not enter the sarcoplasmic reticulum as tetramethylmurexide appears to be able to do (Maylie, J., M. Irving, N.L. Sizto, G. Boyarsky, and W. K. Chandler, 1987. Journal of General Physiology. 89:145-176). After an action potential, the absorbance of either indicator underwent a rapid and transient change that returned to the prestimulus baseline within 100-200 ms. The amplitude of this change had a wavelength dependence that matched the indicator's Ca-difference spectrum. The average amplitude of peak free [Ca] was 21 microM (PDAA or DMPDAA) if all the indicator inside a fiber was able to react with Ca as in cuvette calibrations, and was 26 (PDAA) or 28 microM (DMPDAA) if only freely diffusible indicator could so react. These results suggest that PDAA and DMPDAA are the first Ca indicators that provide a reliable estimate of both the amplitude and time course of (the spatial average of) free [Ca] in a twitch muscle fiber after an action potential.

scholarly journals Simultaneous monitoring of changes in magnesium and calcium concentrations in frog cut twitch fibers containing antipyrylazo III.

1989 ◽  
Vol 93 (4) ◽  
pp. 585-608 ◽  
Author(s):  
M Irving ◽  
J Maylie ◽  
N L Sizto ◽  
W K Chandler
Keyword(s):  
Action Potential ◽  
Voltage Clamp ◽  
Rate Constant ◽  
Time Course ◽  
Average Rate ◽  
Wavelength Dependence ◽  
Phenol Red ◽  
Single Action ◽  
Ph Indicators ◽  
Time Courses

Antipyrylazo III was introduced into frog cut twitch fibers (17-19 degrees C) by diffusion. After action potential stimulation, the change in indicator absorbance could be resolved into two components that had different time courses and wavelength dependences. The first component was early and transient and due to an increase in myoplasmic free [Ca] (Maylie, J., M. Irving, N.L. Sizto, and W.K. Chandler, 1987, Journal of General Physiology, 89:83-143). The second component, usually measured at 590 nm (near the isosbestic wavelength for Ca), developed later than the Ca transient and returned towards baseline about 100 times more slowly. Although the wavelength dependence of this component is consistent with an increase in either free [Mg] or pH, its time course is clearly different from that of the signals obtained with the pH indicators phenol red and 4',5'-dimethyl-5-(and -6-) carboxyfluorescein, suggesting that it is mainly due to an increase in free [Mg]. After a single action potential in freshly prepared cut fibers that contained 0.3 mM antipyrylazo III, the mean peak amplitude of delta A (590) would correspond to an increase in free [Mg] of 47 microM if all the signal were due to a change in [Mg] and all the intracellular indicator reacted with Mg as in cuvette calibrations. With either repetitive action potential stimulation or voltage-clamp depolarization, the delta A (590) signal continued to develop throughout the period when free [Ca] was elevated and then recovered to within 40-90% of the prestimulus baseline with an average rate constant between 0.5 and 1.0 s-1. With prolonged voltage-clamp depolarization, both the amplitude and rate of development of the delta A(590) signal increased with the amplitude of the depolarization and appeared to saturate at levels corresponding to an increase in free [Mg] of 0.8-1.4 mM and a maximum rate constant of 3-4 s-1, respectively. These results are consistent with the idea that the delta A(590) signal is primarily due to changes in myoplasmic free [Mg] produced by a change in the Mg occupancy of the Ca,Mg sites on parvalbumin that results from the Ca transient.

scholarly journals Perturbation of sarcoplasmic reticulum calcium release and phenol red absorbance transients by large concentrations of fura-2 injected into frog skeletal muscle fibers.

1990 ◽  
Vol 96 (3) ◽  
pp. 493-516 ◽  
Author(s):  
P C Pape ◽  
M Konishi ◽  
S Hollingworth ◽  
S M Baylor
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Time Course ◽  
Calcium Release ◽  
Free Calcium ◽  
Phenol Red ◽  
Charge Balance ◽  
Ph Change ◽  
Single Action ◽  
Fura 2

Intact single twitch fibers from frog muscle were studied on an optical bench apparatus after micro-injection with two indicator dyes: phenol red, to monitor a previously described signal (denoted delta pHapp; Hollingworth and Baylor. 1990. J. Gen. Physiol. 96:473-491) possibly reflective of a myoplasmic pH change following action potential stimulation; and fura-2, to monitor the associated change in the myoplasmic free calcium concentration (delta[Ca2+]). Additionally, it was expected that large myoplasmic concentrations of fura-2 (0.5-1.5 mM) might alter delta pHapp, since it was previously found (Baylor and Hollingworth. 1988. J. Physiol. 403:151-192) that the Ca2(+)-buffering effects of large fura-2 concentrations: (a) increase the estimated total concentration of Ca2+ (denoted by delta[CaT]) released from the sarcoplasmic reticulum (SR), but (b) reduce and abbreviate delta[Ca2+]. The experiments show that delta pHapp was increased at the larger fura-2 concentrations; moreover, the increase in delta pHapp was approximately in proportion to the increase in delta[CaT]. At all fura-2 concentrations, the time course of delta pHapp, through time to peak, was closely similar to, although probably slightly slower than, that of delta[CaT]. These properties of delta pHapp are consistent with an hypothesis proposed by Meissner and Young (1980. J. Biol. Chem. 255:6814-6819) and Somlyo et al. (1981. J. Cell Biol. 90:577-594) that a proton flux from the myoplasm into the SR supplies a portion of the electrical charge balance required as Ca2+ is released from the SR into the myoplasm. A comparison of the amplitude of delta pHapp with that of delta[CaT] indicates that, in response to a single action potential, 10-15% of the charge balance required for Ca2+ release may be carried by protons.

scholarly journals Model of Sarcomeric Ca2+ Movements, Including ATP Ca2+ Binding and Diffusion, during Activation of Frog Skeletal Muscle

1998 ◽  
Vol 112 (3) ◽  
pp. 297-316 ◽  
Author(s):  
S.M. Baylor ◽  
S. Hollingworth
Keyword(s):  
Skeletal Muscle ◽  
Action Potential ◽  
Metal Binding ◽  
Time Course ◽  
Current Knowledge ◽  
Diffusion Constant ◽  
Compartment Model ◽  
Half Width ◽  
Frog Skeletal Muscle ◽  
And Diffusion

Cannell and Allen (1984. Biophys. J. 45:913–925) introduced the use of a multi-compartment model to estimate the time course of spread of calcium ions (Ca2+) within a half sarcomere of a frog skeletal muscle fiber activated by an action potential. Under the assumption that the sites of sarcoplasmic reticulum (SR) Ca2+ release are located radially around each myofibril at the Z line, their model calculated the spread of released Ca2+ both along and into the half sarcomere. During diffusion, Ca2+ was assumed to react with metal-binding sites on parvalbumin (a diffusible Ca2+- and Mg2+-binding protein) as well as with fixed sites on troponin. We have developed a similar model, but with several modifications that reflect current knowledge of the myoplasmic environment and SR Ca2+ release. We use a myoplasmic diffusion constant for free Ca2+ that is twofold smaller and an SR Ca2+ release function in response to an action potential that is threefold briefer than used previously. Additionally, our model includes the effects of Ca2+ and Mg2+ binding by adenosine 5′-triphosphate (ATP) and the diffusion of Ca2+-bound ATP (CaATP). Under the assumption that the total myoplasmic concentration of ATP is 8 mM and that the amplitude of SR Ca2+ release is sufficient to drive the peak change in free [Ca2+] (Δ[Ca2+]) to 18 μM (the approximate spatially averaged value that is observed experimentally), our model calculates that (a) the spatially averaged peak increase in [CaATP] is 64 μM; (b) the peak saturation of troponin with Ca2+ is high along the entire thin filament; and (c) the half-width of Δ[Ca2+] is consistent with that observed experimentally. Without ATP, the calculated half-width of spatially averaged Δ[Ca2+] is abnormally brief, and troponin saturation away from the release sites is markedly reduced. We conclude that Ca2+ binding by ATP and diffusion of CaATP make important contributions to the determination of the amplitude and the time course of Δ[Ca2+].

scholarly journals R-CEPIA1er as a new tool to directly measure sarcoplasmic reticulum [Ca] in ventricular myocytes

2016 ◽  
Vol 311 (1) ◽  
pp. H268-H275 ◽  
Author(s):  
Elisa Bovo ◽  
Jody L. Martin ◽  
Jollyn Tyryfter ◽  
Pieter P. de Tombe ◽  
Aleksey V. Zima
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Cardiac Myocytes ◽  
Cellular Localization ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Animal Species ◽  
Ventricular Myocytes ◽  
Myocardial Contraction ◽  
Promising Tool

In cardiomyocytes, [Ca] within the sarcoplasmic reticulum (SR; [Ca]SR) partially determines the amplitude of cytosolic Ca transient that, in turn, governs myocardial contraction. Therefore, it is critical to understand the molecular mechanisms that regulate [Ca]SR handling. Until recently, the best approach available to directly measure [Ca]SR was to use low-affinity Ca indicators (e.g., Fluo-5N). However, this approach presents several limitations, including nonspecific cellular localization, dye extrusion, and species limitation. Recently a new genetically encoded family of Ca indicators has been generated, named Ca-measuring organelle-entrapped protein indicators (CEPIA). Here, we tested the red fluorescence SR-targeted Ca sensor (R-CEPIA1er) as a tool to directly measure [Ca]SR dynamics in ventricular myocytes. Infection of rabbit and rat ventricular myocytes with an adenovirus expressing the R-CEPIA1er gene displayed prominent localization in the SR and nuclear envelope. Calibration of R-CEPIA1er in myocytes resulted in a Kd of 609 μM, suggesting that this sensor is sensitive in the whole physiological range of [Ca]SR. [Ca]SR dynamics measured with R-CEPIA1er were compared with [Ca]SR measured with Fluo5-N. We found that both the time course of the [Ca]SR depletion and fractional SR Ca release induced by an action potential were similar between these two Ca sensors. R-CEPIA1er fluorescence did not decline during experiments, indicating lack of dye extrusion or photobleaching. Furthermore, measurement of [Ca]SR with R-CEPIA1er can be combined with cytosolic [Ca] measurements (with Fluo-4) to obtain more detailed information regarding Ca handling in cardiac myocytes. In conclusion, R-CEPIA1er is a promising tool that can be used to measure [Ca]SR dynamics in myocytes from different animal species.

Mechanisms of inactivation of L-type calcium channels in human atrial myocytes

1997 ◽  
Vol 272 (4) ◽  
pp. H1625-H1635 ◽  
Author(s):  
H. Sun ◽  
N. Leblanc ◽  
S. Nattel
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Time Course ◽  
Atrial Myocytes ◽  
Human Atrial Myocytes ◽  
Whole Cell Patch Clamp ◽  
Dependent Inactivation ◽  
Rapid Inactivation ◽  
Voltage Dependent ◽  
Ca2 Channels

We used whole cell patch-clamp and microfluorimetric (indo 1) techniques to measure Ca2+ current through L-type Ca2+ channels (I(Ca)) and Ca2+ transients in human atrial myocytes. During 1-s depolarizing pulses, I(Ca) inactivation was biexponential. The rate of rapid inactivation was slowed by ryanodine and was correlated with the rate of rise of cytoplasmic free Ca2+ concentration (r = 0.80, P < 0.01). Slower-phase I(Ca) inactivation was not affected by ryanodine but was accelerated by increasing the availability of Ca2+ to permeate the Ca2+ channel. Thus Ca2+ released from the sarcoplasmic reticulum (SR) was responsible for most I(Ca) inactivation during the first 50 ms of a depolarization to 0 mV, and thereafter inactivation by Ca2+ permeating the channel predominated. Pure voltage-dependent inactivation had a much slower time course of development (tau > 2 s) and played a smaller role than Ca2+-dependent mechanisms over a duration comparable to that of an action potential. We conclude that human atrial myocytes show both voltage- and Ca2+-dependent I(Ca) inactivation, that Ca2+-dependent mechanisms predominate over the time course of an action potential, and that although both Ca2+ released from the SR and Ca2+ permeating Ca2+ channels play a role, SR-released Ca2+ is particularly important in early, rapid I(Ca) inactivation, whereas Ca2+ permeating Ca2+ channels is more important in the slower phase of Ca2+-dependent inactivation.

scholarly journals Canine Myocytes Represent a Good Model for Human Ventricular Cells Regarding Their Electrophysiological Properties

2021 ◽  
Vol 14 (8) ◽  
pp. 748
Author(s):  
Péter P. Nánási ◽  
Balázs Horváth ◽  
Fábián Tar ◽  
János Almássy ◽  
Norbert Szentandrássy ◽  
...  
Keyword(s):  
Action Potential ◽  
Time Course ◽  
Laboratory Animals ◽  
Delayed Rectifier ◽  
Ion Currents ◽  
Human Cardiomyocytes ◽  
Ventricular Cells ◽  
Repolarization Reserve ◽  
Electrophysiological Studies ◽  
K Current

Due to the limited availability of healthy human ventricular tissues, the most suitable animal model has to be applied for electrophysiological and pharmacological studies. This can be best identified by studying the properties of ion currents shaping the action potential in the frequently used laboratory animals, such as dogs, rabbits, guinea pigs, or rats, and comparing them to those of human cardiomyocytes. The authors of this article with the experience of three decades of electrophysiological studies, performed in mammalian and human ventricular tissues and isolated cardiomyocytes, summarize their results obtained regarding the major canine and human cardiac ion currents. Accordingly, L-type Ca2+ current (ICa), late Na+ current (INa-late), rapid and slow components of the delayed rectifier K+ current (IKr and IKs, respectively), inward rectifier K+ current (IK1), transient outward K+ current (Ito1), and Na+/Ca2+ exchange current (INCX) were characterized and compared. Importantly, many of these measurements were performed using the action potential voltage clamp technique allowing for visualization of the actual current profiles flowing during the ventricular action potential. Densities and shapes of these ion currents, as well as the action potential configuration, were similar in human and canine ventricular cells, except for the density of IK1 and the recovery kinetics of Ito. IK1 displayed a largely four-fold larger density in canine than human myocytes, and Ito recovery from inactivation displayed a somewhat different time course in the two species. On the basis of these results, it is concluded that canine ventricular cells represent a reasonably good model for human myocytes for electrophysiological studies, however, it must be borne in mind that due to their stronger IK1, the repolarization reserve is more pronounced in canine cells, and moderate differences in the frequency-dependent repolarization patterns can also be anticipated.

scholarly journals Time Course of ECG Depolarization and Repolarization Changes during Ischemia in PTCA Recordings

2004 ◽  
Vol 43 (01) ◽  
pp. 43-46 ◽  
Author(s):  
J. García ◽  
G. Wagner ◽  
R. Bailón ◽  
L. Sörnmo ◽  
P. Laguna ◽  
...  
Keyword(s):  
Time Course ◽  
Wave Amplitude ◽  
Temporal Evolution ◽  
Delayed Response ◽  
S Wave ◽  
Ecg Changes ◽  
T Complex ◽  
Karhunen Loeve Transform ◽  
Low Amplitude ◽  
Electrocardiogram Ecg

Summary Objectives: In this work we studied the temporal evolution of changes in the electrocardiogram (ECG) as a consequence of the induced ischemia during prolonged coronary angioplasty, comparing the time course of indexes reflecting depolarization and those reflecting repolarization. Methods: We considered both local (measured at specific points of the ECG) and global (obtained from the Karhunen-Loève transform) indexes. In particular, the evolution of Q, R and S wave amplitudes during ischemia was analyzed with respect to classical indexes such as ST level. As a measurement of sensitivity we used an Ischemic Changes Sensor (ICS), which reflects the capacity of an index to detect changes in the ECG. Results: The results showed that, in leads with low-amplitude ST-T complexes, the S wave amplitude was more sensitive in detecting ischemia than was the commonly used index ST60. It was found that in such leads the S wave amplitude initially exhibited a delayed response to ischemia when compared to ST60, but its performance was better from the second minute of occlusion. The global indexes describing the ST-T complex were, in terms of the ICS, superior to the S wave amplitude for ischemia detection. Conclusions: Ischemic ECG changes occur both at repolarization and depolarization, with alterations in the depolarization period appearing later in time. Local indexes are less sensitive to ischemia than global ones.

Sign in / Sign up

Export Citation Format

Share Document