[The effect of contrast in light stimulation on the visual evoked response in man].
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Biomedical subjects
Publications and source records attributed to J Peregrin.
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The effect of postextrasystolic potentiation [PESP] on left ventricular [LV] function was assessed by means of left ventricular cineangiography in 26 patients with ischaemic heart disease. Ventricular extrasystoles were induced by a catheter inserted into the LV during injection of the contrast agent. The values of parameters of segmental and global function of LV, found in potentiated and nonpotentiated sinus contractions, were compared. Segmental disturbances present at rest in 13 patients improved or disappeared after extrasystole in 8 patients. Improvements in contraction also took place in segments with normal resting contraction. Global LV function improved significantly; an improvement was observed even without an increase in the LV end-diastolic volume in the postextrasystolic beat. The advantages and limitations of the method for preoperative estimation of the effect of intended myocardial revascularization on the LV function are discussed.
In 25 patients with ischaemic heart disease the effect of nitroglycerin [NTG] on segmental and global function of the left ventricle was assessed by means of left ventricular cineangiography. In 14 patients a segmental disturbance of contraction at rest was found; in six of them the function inproved after NTG. After NTG, the left ventricular diastolic volume, end-diastolic pressure, and systolic blood pressure decreased, the heart rate increased. The global left ventricular function did not significantly change. In patients with ischaemic heart disease NTG helps to differentiate reversible and irreversible disturbances of left ventricular contraction.
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The visual evoked responses (VERs) to blank and checkerboard-patterned stimuli of 6 degrees angular subtense were recorded referentially (OZ--A2) in 10 dark-adapted subjects using a range of 5.27 log units of intensity (maximum luminance = 6420 cd/m2). The mean peak latencies of the prominent positive-negative deflection of the VERs to the blank stimuli exhibit an exponential shortening with the rise of log stimulation intensity. The peak latencies of the positive-negative deflection of the VERs to the checkerboard-pattern stimulation at low and moderate intensities are by about 50 ms shorter, with the latency of the negative peak of the response to the patterned stimulation corresponding to the positive peak latency of the response to the blank stimuli. Accordingly, the VERs to both types of stimulation are of opposite polarity. With a further increase of the stimulation intensity, the latency of the negative peak of the VER to patterned stimulation gradually lengthens due to the glaring effects of the patterned stimuli. Therefore, at high stimulation intensities the VERs to both types of stimuli are of the same polarity. The mean peak-to-peak amplitudes of the VERs to both types of stimulation differ significantly at high-intensity end of the photostimulation range only, the amplitude of the VER to the patterned stimulation being higher.
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