Root Mean Square Voltage Research Articles

Magnetic Nondestructive Evaluation of Creep Behavior in Water-Quenched Modified 9Cr-1Mo Steel

Water-quenched modified 9Cr-1Mo steel was creep tested in the laboratory at a temperature of 600 °C and 125 MPa stress. Magnetic Barkhausen emissions (MBE) measurements were carried out by interrupting the test at different lengths of time. Creep damage in such steel was observed by an increase in root mean square (RMS) voltage of the MBE. The magnetic softening was corroborated with the decrease in pinning density in the material for the coarsening of carbides (M23C6) and formation of massive phases (Fe2Mo), which comes at the expense of a large number of finer carbides. Before failure, the rate of increase in RMS voltage of the MBE decreased due to the demagnetizing field offered by the massive phases. The microstructural analysis was carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) study.

Influence of Sampling Voltmeter Parameters on RMS Measurements of Josephson Stepwise-Approximated Sine Waves

A binary Josephson-array voltage standard was used to investigate the influence of device settings on the reading of an 81/2-digit sampling voltmeter. This voltmeter is the heart of the primary standard for power at 50 Hz or 60 Hz at several National Metrology Institutes (NMIs). In this paper, we present results on the influence of the voltmeter synchronization and measurement parameters on the root-mean-square (RMS) measurements of Josephson stepwise-approximated sine waves for different frequencies. Our results show that for aperture times above 100 mus, the measured RMS voltage shows a large step in value with respect to shorter aperture times and is much more accurate. Furthermore, to obtain 0.2 muV/V accuracy, we show that for stepwise-approximated sine waves at 53 Hz, delay times higher than 10 mus are necessary. A slight delay time dependence limits the accuracy for frequencies above a few hundred hertz.

Effects of angiotensin receptor blockade on serial P-wave signal-averaged electrocardiograms after electrical cardioversion of persistent atrial fibrillation

To evaluate the effects of the angiotensin II type 1 receptor blocker candesartan on P-wave signal-averaged electrocardiogram (P-SAECG) after electrical cardioversion in patients with atrial fibrillation (AF). One hundred and seventy-one patients with persistent AF were randomized to receive candesartan 8 mg/day or placebo for 3-6 weeks before and candesartan 16 mg/day or placebo for 6 months after electrical cardioversion. P-SAECG was recorded in 114 patients (57 in each treatment group) after cardioversion and repeated in those with sinus rhythm at 1 and 6 weeks, and 3 and 6 months. Filtered P-wave duration (FPD), root-mean-squared (RMS) voltages of the terminal 40 ms of the filtered P-wave, RMS voltage of the entire filtered P-wave, and the integral of the voltages in the entire PD were analysed. No effects of candesartan were observed on any P-SAECG parameter at baseline. In the subgroup of patients in sinus rhythm after 6 months, FPD was significantly shorter both at baseline (151 +/- 16 vs. 163 +/- 16 ms) and at 6 months (143 +/- 12 vs. 153 +/- 15 ms) in the candesartan (n = 15) compared with the placebo group (n = 21). Treatment with candesartan was associated with a shorter FPD in patients remaining in sinus rhythm for 6 months.

Temporal and postural variation of 12-lead high-frequency QRS electrocardiographic signals in asymptomatic individuals

Because changes in the 12-lead high-frequency QRS electrocardiogram (HF QRS ECG) more sensitively identify myocardial ischemia than do changes in the ST segments of the conventional ECG, it is important that changes in HF QRS signals that are merely physiological be distinguishable from those that are potentially pathological. We therefore studied the temporal variation of HF QRS measures such as root mean square (RMS) voltage and the presence vs absence of reduced amplitude zones (RAZs) in 107 asymptomatic individuals in the supine position during a brief period of ECG monitoring. In addition, to ascertain the effects of posture on the 12-lead HF QRS ECG, we collected additional seated data from 25 of these individuals and estimated the fifth and 95th percentile of the percent relative change between the supine and seated measurements. In all cases, variation of HF QRS parameters decreased as the number of beats in the signal average increased. For example, in the supine position, the 95th percentile of the percent relative change between consecutive within-lead measurements of RMS voltage for a 50-beat signal average was 12.3% but decreased to 11.7%, 11.2%, and 10.7% for 75, 100, and 150 beat signal averages, respectively ( P < .01). After transition from the supine to the seated upright position, changes in some measures of HF QRS were statistically significant, with RMS voltage decreasing significantly in lead V 3 and with the number of RAZs lost in the 12-lead HF QRS ECG significantly exceeding the number of RAZs gained. We conclude that most measures of HF QRS ECG are sufficiently stable for routine continuous monitoring.

The effects of amount and frequency of alternating current used in water bath stunning and of slaughter methods on electroencephalograms in broilers

AbstractThe effectiveness of electrical water bath stunning of 172 individual broilers for 1 s with a constant root mean square (RMS) current of 100, 150 or 200 mA, delivered using a variable voltage/constant current stunner with 200, 400, 600, 800, 1000, 1200 or 1400 Hz sine wave alternating current (AC), followed by slaughter using a unilateral or ventral neck-cutting procedure, was evaluated. A binary logistic regression of broilers showing epileptiform activity or not following stunning showed that both the electrical frequency (Hz) and RMS current (mA) had a significant effect on the probability of the electroencephalogram (EEG) manifestation. The univariate analysis of variance showed that the time to the onset of less than 10% of the pre-stun relative power contents was significantly affected only by the interaction between electrical frequency and slaughter method. A similar analysis of variance of the time to reach less than 10% of the pre-stun total power content showed slaughter method, RMS current, the slaughter method/frequency interaction and the RMS current/frequency interaction to be either significant or approaching significance. Based on these results it is recommended that effective water bath stunning of broilers with a minimum constant current of 100, 150 and 200 mA could be achieved with electrical frequencies of up to 200, 600 and 800 Hz, respectively. In addition, It is likely that electrical frequencies of above 800 Hz would have required a minimum current of greater than 200 mA to induce epileptiform activity in the EEGs of broilers.

Effects of cholinergic medication on EEG delta and theta activity during REM sleep in old age: implications for sleep-related memory consolidation

Research suggests that REM sleep theta and delta oscillations as well as phasic components may play an important role in memory consolidation. REM sleep increases following administration of an AChE-I were found to be associated with improved memory consolidation in older adults. Whether such benefits may also be associated with higher EEG theta and delta activity during REM sleep was investigated. Forty-two participants (mean age=65.4±4.6, 57% female) received 5mg of the AChE-I donepezil in a placebo-controlled, double-blind design. Mean root mean square (RMS) voltages in EEG delta (1–4 Hz) and theta (4–8 Hz) frequency bands were calculated for total and phasic REM sleep as well as total sleep time. As reported earlier, participants of the medication group showed significant benefits in sleep-related memory consolidation (p<.05). A trend for higher mean delta RMS voltages in the medication group was found for total REM sleep (p<.10), this effect being more pronounced for phasic REM sleep (p<.05). The groups did not differ in mean delta RMS voltages of total sleep time. No significant effects were found for mean theta RMS voltages. Hence, the AChE-I donepezil seems to enhance EEG delta activity during phasic REM sleep in old age, which may partly explain its beneficial effects on sleep-related memory consolidation in older adults.

Prognostic significance of serial P wave signal-averaged electrocardiograms following external electrical cardioversion for persistent atrial fibrillation: a prospective study.

The authors hypothesized that the persistence of abnormal atrial conduction detected by serial P wave signal-averaged electrocardiograms (P-SAECGs) can identify patients who are at high risk of recurrent atrial fibrillation (R-AF) following electrical cardioversion (ECV). P-SAECGs were recorded in 60 consecutive patients after ECV (53 men, age 66 +/- 10 years) and repeated in those who had remained in sinus rhythm (SR) 1 week, and 1, 3, and 6 months later. Filtered P wave duration (PD), root mean square (RMS) voltage of the terminal 40, 30, 20 ms (RMS-40, RMS-30, RMS-20) of the filtered P wave, RMS voltage of the entire filtered P wave (RMS-p), and the integral of the voltages in the entire P wave (integral-p) were analyzed. Thirty-one (52%) patients returned to AF within 1 week, an additional 11 (18%) by 1 month, and a further 2 (3.3%) at each subsequent assessment (3 and 6 months). The patients with R-AF had longer PD (157 +/- 24 vs 143 +/- 17 ms, P < 0.0001) and lower RMS-40, RMS-30, RMS-20 (5.3 +/- 2.0 vs 6.1 +/- 3.4 microV, P = 0.007; 4.3 +/- 1.5 vs 5.7 +/- 3.2 microV, P < 0.0001; 3.6 +/- 1.4 vs 5.2 +/- 3.0 microV, P < 0.0001, respectively) than those who remained in SR. These measurements did not change significantly in either group. RMS-p increased in SR patients (P = 0.009) but decreased in those who subsequently reverted to AF (P = 0.032) with a significant difference between the slopes of the RMS-p change (P = 0.006). Integral-p decreased from the time of ECV in the R-AF group only (P = 0.0028) and created a significant difference between the two slopes (P = 0.0004). The evolution of P-SAECG parameters after ECV differs in patients whose AF recurs versus patients who remain in SR.

Ａｌ‐Ｍｇ‐Ｓｉ合金の引張試験におけるＡＥ特性に及ぼす過剰シリコン，時効条件の影響

Acoustic emission (AE) behavior during tensile deformation and fracture was investigated for Al–Mg–Si base alloys with and without excess silicon. In as-quenched specimens, a peak of AE event counts was observed only at a yield point and then it reduced with increment in plastic strain. The AE activity at the yield point increased with the amount of silicon content. AE signals associated with yielding had mainly its amplitude ranges below 60dB. Change in root mean square (RMS) voltage with deformation well corresponds to that of the AE event counts. On the other hand, in the T6–aged specimen, the peak of AE counts appeared not only at the yield point but also at the occurrence of intergranular fracture. AE signals associated with the intergranular fracture had its amplitude ranges up to 100 dB. The change of RMS voltage revealed that high AE energy was released from the specimen when the intergranular fracture occurred.

Electrornyographic activity of the biceps brachii muscle in shoulders with anterior instability

Purpose: The purpose of this study was to evaluate the activity of the biceps muscle in the vulnerable abduction and external rotation position of the shoulder in patients with anterior instability. Type of Study: This experimental study included a prospective analysis of the electromyographic (EMG) data on a group of patients with traumatic unilateral anterior instability of the shoulder. The EMG data of the unstable shoulders was compared with those of the opposite shoulders as control. The optimal sample size for the case-control study was calculated using an nQuery Advisor program (nQuery Advisor 3.0, Statistical Solutions, Cork, Ireland). Methods: The EMG analyses were conducted in 76 shoulders in 38 patients who had a traumatic anterior instability in 1 shoulder. The EMG records were obtained at different positions of the shoulder, which included 0°, 45°, 90°, and 120° of shoulder abduction. In each angle of shoulder abduction, the arms were placed in an external rotation as tolerated by the anterior apprehension. The paired-sample t test was used to compare the difference of the root mean square (RMS) voltages between the stable and unstable shoulders in each degree of arm position. Results: The RMS voltage of the biceps muscle was significantly greater in the unstable shoulder than the opposite stable shoulder in all positions of the arm (P = .00). The RMS voltage of the biceps was maximal at 90° and 120° of external rotation in the unstable shoulder (P < .05). The RMS voltage of the supraspinatus muscle revealed no differences in any of the test conditions (P = .904, .506, .119, and .781 in 0°, 45°, 90°, and 120°, respectively). Conclusions: In the vulnerable abduction and externally rotated position, the biceps muscle plays an active compensatory role in the unstable shoulder but not in the stable shoulder.

Electromyographic activity of the biceps brachii muscle in shoulders with anterior instability

Purpose : The purpose of this study was to evaluate the activity of the biceps brachii muscle in the vulnerable abduction and external rotation position of the shoulder in patients with anterior instability. Materials and Methods: This experimental study include a prospective analysis of the electromyographic(EMG) data on a group of patients with traumatic unilateral anterior instability of the shoulder. The EMG data of unstable shoulders was compared with those of opposite shoulders as control. The optimal sample size for the case-control study was calculated using an nQuery Advisor program(nQuery Adviser 3.0, Statisticl solutions Ltd., Ireland). The EMG analyses were conducted in 76 shoulders in 38 patients who had a traumatic anterior instability in one shoulder. The EMG records were obtained at different position of shoulder, which included 0° , 45° , 90° and 120° of shoulder abduction. In each angle of shoulder abduction, the arms were placed in an external rotation as tolerated by the anterior apprehension. The paired-sample T test was used to compare the difference of the root mean square(RMS) voltages between the stable and unstable shoulders in each degree of arm position. Results : The RMS voltage of the biceps muscle was significantly greater in the unstable shoulder than opposite stable shoulder in all position of the arm(p

Effects of half ironman competition on the development of late potentials.

The primary purpose was to evaluate the prevalence of late potentials (LPs) in triathletes before and after a half ironman triathlon. The secondary purpose was to examine whether LPs are the electrocardiographic expression of a greater myocardial mass. Nine asymptomatic male triathletes (mean age +/- SD, 32 +/- 5 yr) were examined using signal-averaged ECG (SAECG) 48-72 h before (PRE), immediately after (POST), and 24-48 h after the completion (RECOVERY) of a half ironman triathlon. Late potentials were considered to be present if two of the following SAECG anomalies were observed: 1) a prolonged filtered QRS (/QRS) complex (> or = 114 ms), 2) a lengthened low amplitude signal (LAS) duration (>38 ms), and/or 3) a low root mean square (RMS) voltage of the last 40 ms of the fQRS (<20 microV). Left ventricular dimensions were determined at PRE using M-mode echocardiography. There were no significant differences between PRE, POST, and RECOVERY in the fQRS duration, the LAS duration, or the RMS voltage. Two athletes displayed a single SAECG abnormality during PRE and two SAECG anomalies (i.e., LPs) during POST. Late potentials remained in one of the two athletes during RECOVERY. A moderate relationship existed between fQRS and left ventricular mass (r = 0.67, P < 0.05). Ultra-endurance training and/or events do not lead to LPs in the majority of triathletes who do not possess ventricular arrhythmias. However, a small subset of triathletes do display SAECG anomalies, which are augmented by an ultra-endurance event and may persist even after recovery from the event. Left ventricular mass does not affect overall SAECG parameters.

Prevalence of late potentials in a sample of 487 healthy, middle-aged men from southwestern France.

Late potentials (LPS) have been shown to be predictive of ventricular tachycardia in coronary artery disease subjects, but the prevalence of LP in the general population is not as well-known. The study included 487 men without a history of cardiovascular disease (aged 50-59) living in Southwestern France. Standard-averaged high resolution electrocardiogram was performed using Butterworth filtering at 40-250 Hz. LPS were defined as two or more of the following criteria: QRS > 114 ms, duration of the low amplitude signals in the terminal portion of QRS > 38 ms, root mean square (RMS) voltage of the last 40 ms < 20 microV. The mean QRS duration was 97 +/- 12 ms (mean +/- SD), duration of the low amplitude signals in the terminal portion of QRS was 32 +/- 10 ms, and RMS voltage in the last 40 ms was 39 +/- 27 microV. Eight percent of subjects (95% confidence interval [CI]: 6%-11%) had a QRS duration > 114 ms; 22% (95% CI: 18%-26%) had a duration of low amplitude signals > 38 ms, and 25% (95% CI: 22%-29%) had RMS voltage in the last 40 ms < 20 microV. Finally, the prevalence of LP was 21% (95% CI: 18%-25%). In conclusion, according to commonly used criteria, the prevalence of LP in this healthy population of middle-aged men is 21%, close to the values found in the literature for myocardial infarction patients. Those findings indicate the need for reconsidering the definition of LPS.

The acute effects of radiofrequency energy in articular cartilage: An in vitro study

The purpose of this investigation was to determine the acute effect of radiofrequency (RF) energy on articular cartilage. Six fresh human articular cartilage specimens were obtained from patients undergoing total knee arthroplasty for unicompartmental osteoarthritis. A jig was used as the RF-energy was delivered to 2 designated treatment areas. These areas included a normal and a diseased area of articular cartilage tested at 3 voltage settings (kilohertz per voltage root mean square), 133 to 147 (setting 2), 161 to 179 (setting 4), and 190 to 210 (setting 6) for 3 seconds. The designated testing areas were marked with tissue dye and processed using standard histological techniques. A scalloped concave excavation with a smooth surface remains at each treatment site. The chondrocytes are viable at the RF-treated sites without alterations in nuclear cytoplasmic nor lacunae structure when compared with collateral untreated areas. In conclusion, chondrocytes remain viable, no collagen abnormalities are detected, and diseased areas are smoothed without further evidence of fibrillation. RF-energy appears to be safe for use on articular cartilage.

Effect of different stages of tensile deformation on micromagnetic parameters in high-strength, low-alloy steel

The influence of tensile deformation on the magnetic Barkhausen emissions (MBE) and hysteresis loop has been studied in a high-strength, low-alloy steel (HSLA) and its weldment. The magnetic measurements were made both in loaded and unloaded conditions for different stress levels. The rootmean-square (RMS) voltage of the MBE has been used for analysis. This study shows that the preyield and postyield deformation can be identified from the change in the the MBE profile. The initial elastic deformation showed a linear increase in the MBE level in the loaded condition, and the MBE level remained constant in the unloaded condition. The microplastic yielding, well below the macroyield stress, significantly reduces the MBE, indicating the operation of grain-boundary dislocation sources below the macroyield stress. This is indicated by the slow increase in the MBE level in the loaded condition and the decrease in the MBE level in the unloaded condition. The macroyielding resulted in a significant increase in the MBE level in the loaded condition and, more clearly, in the unloaded condition. The increase in the MBE level during macroyielding has been attributed to the grain rotation phenomenon, in order to maintain the boundary integrity between adjacent grains, which would preferentially align the magnetic domains along the stress direction. With progressive plastic deformation, the MBE level remains more or less constant in the loaded condition and decreases linearly with strain in the unloaded condition. This constant MBE behavior in the loaded condition is attributed to the opposing effect of applied tensile stress (which tends to align the domains along the stress direction) and the dislocation density (which reduces the domain-wall displacement). The decreasing MBE in the unloaded condition is attributed to the combined effect of compressive residual stress at the surface layers (which tends to align the domain wall perpendicular to the stress direction) and the dislocation density. This study shows that MBE during tensile deformation can be classified into four stages: (1) perfectly elastic, (2) microplastic yielding, (3) macroyielding, and (4) progressive plastic deformation. A multimagnetic parameter approach, combining the hysteresis loop and MBE, has been suggested to evaluate the residual stresses.

The salivary amylase, lactate and electromyographic response to exercise.

Twelve trained young males (age: 24 +/- 5 years) performed an incremental test to exhaustion during which capillary blood and saliva samples were obtained to determine the blood lactate (LT) and salivary amylase (T(sa)) thresholds. The root mean-square voltage of electromyographic activity (rms-EMG) of the vastus lateralis muscle was also recorded to detect the electromyographic threshold (EMG(T)). No significant difference was found between the exercise intensity corresponding to the LT, T(sa) or EMG(T).

Signal-averaged electrocardiograms in normal Doberman pinschers.

Signal-averaged electrocardiograms (SAECGs) were performed on nonsedated normal dogs in left-lateral recumbency. Following signal averaging, both time-domain and 3-dimensional frequency-domain analyses were performed. For time-domain analysis, the high-frequency QRS (HFQRS) duration, duration of the terminal QRS complex less than 40 microV (LAS40), and root mean square (RMS) voltages (microV) of the terminal 40 milliseconds (RMS40) and 30 milliseconds of the QRS complex were calculated. For frequency-domain analysis, correlation ratios were calculated for 30-, 40-, 50-, and 60-millisecond segment lengths begun 10, 15, or 20 milliseconds before the end of the QRS complex. Spectro-temporal mapping was also performed. All of the parameters of the SAECGs analyzed in the time domain were associated with each other. LAS40 and RMS voltages regressed significantly (P < .0000) on the HFQRS duration. Ninety-five percent of the HFQRSs were 55-75 milliseconds, 95% of the LAS40s were 9-26 milliseconds, and 95% of the RMS40 voltages were 177-444 microV. None of the SAECGs contained evidence of ventricular late potentials. Spectro-temporal maps were similar in each dog when the same segment lengths and starting points were compared. No evidence of ventricular late potentials was observed. Correlation ratios were lower when windowed segments included 15 or 20 milliseconds (versus 10 milliseconds) of the terminal QRS complex. When only 10 milliseconds of the terminal QRS complex were included in windowed segments, the mean correlation ratios for 30- and 40-millisecond segment lengths were > 0.8 and > 0.61 in 67% of all analyses, respectively.

Analysis of the P wave with signal averaging to assess the risk of atrial fibrillation after coronary artery bypass surgery.

P wave signal averaging was performed in 91 consecutive patients undergoing coronary artery bypass grafting to detect patients at risk of postoperative atrial fibrillation (AF). Sixteen patients (17.5%) developed AF after surgery. The P wave duration on the signal-averaged electrocardiogram (ECG) and on surface ECG was prolonged in AF patients compared to others (respectively 141 +/- 12 vs. 132 +/- 12 ms and 124 +/- 9 vs. 113 +/- 9 ms). The root mean square voltages (RMS) of the total P wave were not different between the two groups; the RMS of the late portion of the P wave (late RMS) was significantly higher (0.25 +/- 0.15 vs. 0.17 +/- 0.10 microV) and the RMS of the first 110 ms of the P wave (early RMS) significantly lower (0.88 +/- 0.28 vs. 1.09 +/- 0.33 microV) in AF. The late/ early RMS ratio was different (0.29 +/- 0.16 vs. 0.17 +/- 0.11). In a multivariate analysis only age and the late/early RMS ratio were predictive for AF.

Evaluation of signal-averaged electrocardiogram in healthy obese women: effects of subcutaneous adipose tissue.

To determine the correlations between signal-averaged electrocardiography (SAECG) indices and various anthropometric parameters in obese women. Twenty-seven healthy obese women (mean age 29.7 +/- 9.6 y, mean body mass index 35.2 +/- 6.0 kg/m2). SAECG was performed using a Marquette, MAC 12/15 system. Bidirectional filtering, low-pass filtering 250 Hz and 25, 40 and 80 Hz high-pass filter settings were employed on the same averaged beats. At least 200 beats were averaged to achieve a noise level <1 microV. Body mass index, waist to hip circumference ratio, neck circumference, arm circumference and conicity index were determined for all subjects. Skinfold thicknesses were measured in triceps, biceps, subscapular, supra-iliac and para-umbilical regions. Significant correlations were observed between the root mean square (RMS) voltage of the terminal 40 ms of the filtered ORS complex at 25 and 40 Hz and skinfold thicknesses measured at different sites. Significant correlations were obtained between the noise level at 25 and 40 Hz and skinfold thicknesses measured at subscapular, biceps and triceps regions also. The only SAECG parameter correlated significantly with the noise level was the RMS voltage at 25 and 40 Hz high-pass filter settings. In obese women SAECG must be performed with 80 Hz high-pass filter setting which eliminates the random noise originating from the subcutaneous adipose tissue. In addition RMS voltage which shows positive linear correlations with the noise level of 25 and 40 Hz high-pass filter settings might be inappropriate for the definition of abnormal SAECG criteria in obese women.

Signal-averaged electrocardiography in healthy children: influence of age, body size, and gender.

Our objective was to determine influence of age, body size, and gender on SAECG signals and to establish normal range for standard SAECG parameters in the pediatric population. Five hundred thirty healthy children and adolescents (290 males, 240 females) aged 6.0-17.3 years were studied with high resolution ECG. Patients were divided into five age groups, and each age group was divided in two subgroups according to gender. Parameters studied were filtered QRS duration, root mean square (RMS) voltage of the last 40 ms and of the last 30 ms of the filtered QRS complex, and duration of the terminal waveform of the filtered QRS < 40 microV of amplitude (LAS). After validation of the distribution of the various variables, means, standard deviations, and 95% confidence intervals were determined for each SAECG parameter at 25- to 250-Hz filtering and at 40- to 250-Hz filtering for the ten subgroups. There was a significant age and body surface area (BSA)-associated increase in filtered QRS duration in boys and girls, and a decrease in RMS voltage of the end of the QRS complex in girls. In addition, girls had a significantly shorter QRS and longer LAS durations than boys. These differences of signal-averaged signals between genders were not related to age or body size differences since analysis of covariance with age at evaluation or BSA as covariates showed the same trend. Three children (0.6%) had a SAECG out of normal range for age for the four parameters studied either at 25- or 40-Hz high pass filter. Due to the large sample studied, our results provide a basis for interpretation of SAECG in children. Normal ranges for the various variables were determined, and it appeared that adjustments for age, body size, and gender are mandatory when studying SAECG in children.

Normal values and methodologic recommendations for signal-averaged electrocardiography in children and adolescents

Signal-averaged electrocardiography was performed in 153 normal children and adolescents (1 day to 18.3 years old) to examine the effects of age, sex, and race on different electrocardiographic variables, and to evaluate whether the current methods for analysis of the signal-averaged electrocardiogram are applicable to small children. Tracings with inaccurate automatic determination of the QRS end point or high noise levels were excluded. Filtered QRS duration, root-meansquare voltage, and low-amplitude signal duration were measured using 25, 40, and 80 Hz filters. All variables were significantly different (p < 0.01) in infants compared with subjects aged >15 years. These differences gradually resolved with increasing age. Sex differences were present for some variables in adolescents only, and there was no significant race-related difference. Because of the shorter QRS duration, the terminal activities were more accurately reflected at the terminal duration of 30 ms in infants and 35 ms in children aged at least 1 year to <6 years. Normative data for filtered QRS duration, root-mean-square voltage, and low-amplitude signal duration are provided for different age groups.