threshold

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threshold

 [thresh´old]
1. the level that must be reached for an effect to be produced, as the degree of intensity of stimulus that just produces a sensation.
2. that value at which a stimulus just produces a sensation, is just appreciable, or comes just within the limits of perception.
auditory threshold the slightest perceptible sound.
threshold of consciousness the lowest limit of sensibility; the point of consciousness at which a stimulus is barely perceived.
defibrillation threshold DFT; the minimum amount of energy in joules that will consistently terminate ventricular fibrillation.
fibrillation threshold the least intensity of an electrical impulse that will cause cardiac tissue to begin fibrillation.
pacing threshold the minimal electrical stimulus required to produce consistent cardiac depolarization.
renal threshold that concentration of a substance (threshold substance) in plasma at which it begins to be excreted in the urine.
sensing threshold in cardiac pacing terminology, the voltage of the minimum signal that consistently activates pulse generator function.

thresh·old

(thresh'ōld), Avoid the misspelling/mispronunciation threshhold.
1. The point at which a stimulus first produces a sensation.
2. The lower limit of perception of a stimulus.
3. The minimal stimulus that produces excitation of any structure, for example, the minimal stimulus eliciting a motor response.
Synonym(s): limen (2) [TA]
[A.S. therxold]

threshold

(thrĕsh′ōld′, -hōld′)
n.
The point that must be exceeded to begin producing a given effect or result or to elicit a response: a low threshold of pain.

threshold

Medtalk The point, stage, or degree of intensity at which a particular effect occurs or action is taken. See Therapeutic threshold, Transfusion threshold.

thresh·old

(thresh'ōld)
1. The level of intensity at which a stimulus first produces a sensation.
2. The lower limit of perception of a stimulus.
3. The minimal stimulus that produces excitation of any structure.
4. Synonym(s): limen.
[A.S. therxold]

threshold

the level at which a STIMULUS results in a response and below which there is no response despite the application of a stimulus.

threshold 

The value of a stimulus that just produces a response. Syn. limen.
absolute threshold The minimum luminance of a source that will produce a sensation of light. It varies with the state of dark adaptation, the retinal area stimulated, the wavelength of light, etc. Syn. light threshold. See photochromatic interval.
contrast threshold See differential threshold.
corneal touch threshold See corneal touch threshold.
differential threshold The smallest difference between two stimuli presented simultaneously that gives rise to a perceived difference in sensation. The difference may be related to brightness, but also to colour and specifically to either saturation (while hue is kept constant) or hue (while saturation is kept constant). The differential threshold of luminance is equal to about 1% in photopic vision. Syn. contrast threshold (if the difference is one of luminance); just noticeable difference (jnd). See Weber's law; contrast sensitivity.
light threshold See absolute threshold.
movement threshold 1. The minimum motion of an object that can be perceived. 2. The speed at which an object moving between two points just appears to be moving. See hyperacuity; phi movement.
resolution threshold See limit of resolution.
stereo-threshold See stereoscopic visual acuity.

thresh·old

(thresh'ōld) Avoid the misspelling threshhold.
1. Point at which a stimulus first produces a sensation.
2. Lower limit of perception of a stimulus.
[A.S. therxold]
References in periodicals archive ?
Our study does not yield any relationship between pacing threshold values and severity and distribution of CAD.
This study investigated the effect of CAD severity, distribution and LVEF on acute ventricular pacing threshold and lead impedance at the time of pacemaker implantation.
Comparison of EF, pacing threshold and impedance values in ICD and PM groups Variables ICD Group (n=43) PM Group (n=89) * p EF, % 34.1 [+ or -] 16.4 47.2 [+ or -] 8.8 0.000 Impedance, ohm 903.3 [+ or -] 213.6 996.7 [+ or -] 309.4 0.046 Threshold, volt 0.5 [+ or -] 0.2 0.4 [+ or -] 0.1 0.032 Continuous variables are expressed as mean [+ or -] SD * Independent samples t-test EF--ejection fraction, ICD--implantable cardiac defibrillator, PM--pacemaker Table 2.
Ventricular pacing thresholds, impedance values and ejection fractions of the two groups were compared.
Ventricular pacing thresholds were significantly higher, impedance values and ejection fractions were found significantly lower in the ICD group, compared with the PM group (p<0.05), (Table 1).
No statistically significant difference was found between the subgroups in terms of pacing thresholds and impedance (p>0.05) (Table 3).
To our knowledge, there is no published study, which investigates the effect of severity and distribution of coronary artery disease on pacing thresholds and impedance values.
At implant, LV pacing thresholds were similar between the groups, however, at 3-month follow-up, stimulation thresholds increased significantly in patient group with low LVEF (<40%).
The pacing threshold (and current strength) can be reduced by modifying certain parameters: the position of pacing electrodes, construction of electrodes, distance between electrodes and the duration and shape of the pulse.
In more than half of the cases using the proposed method there was no accompanying significant increase of atrial pacing threshold. We expect to find an optimal combination of pulses to reduce the pain sensation during transesophageal pacing.
Transesophageal atrial pacing threshold: role of interelectrode spacing, pulse width and catheter insertion depth.
Pacing thresholds Threshold, Reference With chest electrode mA Patient Success Patient count Success rate, % count rate, % 7 1 3 0 8 0 3 4 12 9 1 6 5 26 10 1 9 5 41 11 5 24 5 56 12 6 41 4 68 13 5 56 5 82 14 4 68 2 88 15 2 74 88 16 7 94 2 94 17 1 97 94 18 97 2 100 19 1 100 100 Table 3.