High-pass Filter Settings Research Articles

High-pass filter settings affect the detectability of MLRs in humans

Auditory middle latency responses (MLRs) have been recorded in 217 patients ranging in age from 6 days to 20 years. The probability of obtaining MLR components Na and Pa was higher with a high-pass filter setting of 15 Hz, 12 dB/octave as compared to 3 Hz, 6 dB/octave. This effect was found at all ages tested. Age-related latency effects were apparent with 3 Hz but not 15 Hz filtering.

Rate and filter effects on the developing middle-latency response.

Auditory middle-latency responses (MLRs) were obtained from 71 unanesthetized gerbils ranging in age from 10 to greater than 90 days. Effects of age, stimulation rate, high- and lowpass filter settings and filter slope were examined. MLR amplitude decreased significantly with increased stimulation rate at all ages, at rates up to 40/s. The detection of MLR waves (presence or absence) varied inversely with the rate of stimulation only in immature subjects. The amplitude of waves B (15 ms) and C (25 ms) was significantly larger with a highpass filter setting of 3 Hz as compared to 10 and 30 Hz. This effect was significantly more pronounced in developing animals as compared to adults. MLR amplitude was greater with a filter slope of 6 dB/octave as compared to 48 dB/octave, (10-2,000 Hz) and this effect was also significantly greater in developing animals than in adults. There was no interaction between lowpass filter setting and age (100 vs. 2,000 Hz). A prominent positive wave occurring at approximately 50 ms was present in the 48 dB/octave condition although it was not observed with 6 dB/octave filtering. The clinical use of the MLR requires a better understanding of the effects of stimulus and recording procedures on the response, and how they vary as a function of subject age.

Technical aspects of brainstem evoked potential audiometry using tones.

The brainstem response to brief tones contains a large vertex-positive component. If high-pass filter settings above 20 Hz are used, particularly with high rolloff slopes, the morphology of the response changes so that a vertex-negative wave becomes the most prominent component of the response. The amplitude of the response is unaffected by stimulus presentation rates of up to 35/sec. Tones with longer rise times have greater frequency specificity, but at rise times of greater than 5 msec, the brainstem response becomes very small. At high intensities, regardless of the rise time, the response to tones is not completely frequency specific, and notched noise masking should be used to obtain frequency-specific responses.

The Indian Medical Service

<h3>Abstract</h3> <h3>Objective</h3> The characteristics of discrete intracardiac electrograms in selective left bundle branch (SLBB) pacing (SLBBP) have not been described in detail previously. This study aimed to examine the effect of different high-pass filter (HPF) settings on discrete ventricular components in an intracardiac electrogram (EGM) and to analyze its possible mechanisms. <h3>Methods</h3> This study included 95 patients with indications of permanent cardiac pacing. EGMs were collected at four different HPF settings (30, 60, 100, and 200 Hz) with a low-pass filter at 500 Hz, and their possible mechanisms were analyzed. <h3>Results</h3> LBBP was successfully achieved in 92.6% (88/95) of patients. SLBBP was achieved in 80 patients. The occurrence rates of discrete EGM were 18.9%, 40.0%, 74.7%, and 84.2% for HPF settings of 30 Hz, 60 Hz, 100 Hz, and 200 Hz, respectively. The analysis of discrete ECG detection showed significant differences between the different HPF settings. By using the discrete EGM as the SLBB capture golden standard, the results of EGMs revealed that the 30 Hz HPF has a sensitivity of 23% and specificity of 100%. The 60 Hz HPF had a sensitivity of 48% and a specificity of 100%. The 100 Hz HPF had a sensitivity of 89% and a specificity of 100%. The 200 Hz HPF had a sensitivity of 100% and specificity of 100%. <h3>Conclusions</h3> An optimal HPF setting of 200 Hz is recommended for discrete electrogram detection. A discrete EGM should exhibit an isoelectric interval. A <b>steep</b> deflection and spinous ventricular EGM morphology nearly identify an intrinsic EGM morphology.