Criteria for evaluating abnormal signal-averaged electrocardiogram in children classified by age, body surface area and height

Signal-averaged electrocardiography in normal newborn infants

Signal-averaged electrocardiograms (SAECGs) were recorded with bipolar orthogonal and standard 12-lead settings in 29 term healthy newborn infants. SAECGs performed with the two lead configurations were similar in quality and quantity. For the duration of the QRS complex (QRSD), the upper limit of normality for newborn infants can be set to 100 ms. It is similar in individual bipolar orthogonal and individual standard 12-lead recordings as well as in filtered QRSD in the vectorcardiograms (the vector magnitude, VM, and the sum of extremity leads). In individual leads of bipolar orthogonal and standard 12-lead recordings, root-mean-square voltage of the terminal 40 ms of the QRS complex (RMS40) is widely scattered and unsuitable as discriminant variable. For VM and the sum of the extremity leads, the same reference values for RMS40 and duration of low-amplitude signal can be used as applied in adults. Individual lead recordings provide complementary information in addition to vectorcardiograms. There are practical advantages using standard 12-lead compared to conventional bipolar orthogonal configurations. The widespread use of standard 12-lead ECG in routine medical practice makes its utility advantageous also in performing signal-averaged electrocardiography.

Longitudinal estimation of signal-averaged electrocardiograms in patients with Kawasaki disease

BACKGROUND

Myocarditis associated with Kawasaki (KD) disease is prominent, but rarely detected by conventional methods. The hypothesis of this study is to see if signal-averaged electrocardiogram can detect myocarditis with KD.

METHODS

We obtained signal-averaged electrocardiograms from 71 patients with KD (mean age 2.8 +/- 2.9 years) in the acute (1st-4th week), subacute (5-7th week), and chronic (8th week or later) phases (mean study period 3.5 +/- 1.7 years). Sixteen patients who had pericardial effusion, bundle branch block or myocardial ischemia were excluded from this study. The results were compared with those of Holter and 12-lead electrocardiograms, echocardiography and serum myocardial enzymes. They were also contrasted with the course of each patient.

RESULTS

The incidence of abnormal findings on signal-averaged electrocardiogram was 18.2% in the acute phase versus 10.9% in the subacute and chronic phases. It differed significantly higher than the other conventional tests (P < 0.05). Four patients had abnormalities of signal-averaged electrocardiograms through all three phases. Among these four, two had reduced left ventricular contractility. However, these changes were transient and resolved in the subacute phase. All patients had good courses and no residue.

CONCLUSION

This study shows the possibility that signal-averaged electrocardiogram is more useful to detect myocarditis associated with KD than the other conventional tests. However, we could not define the prognostic value of abnormal signal-averaged electrocardiograms during this study period.

Normal values of signal-averaged electrocardiographic parameters and QT dispersion in infants and children

Ventricular late potentials, and dispersion of the QT interval, are markers for risk of ventricular arrhythmias. Normal values for these parameters are well established in adults, but may not apply for children. This study has investigated the age dependency of signal averaged electrocardiographic parameters and QT dispersion in 111 normal children aged from 5 days to 16 years. The results indicate that parameters change with age: duration of filtered QRS and low amplitude (< 40 microV) terminal signal increase with age, especially in the younger patients. Filtered QRS is 88.9 +/- 7.87 ms in infants, and increases to 108.7 +/- 8.51 in teenagers (p<0.001). Low amplitude terminal signals are 17.0 +/- 3.44 ms in infants, and 24.5 +/- 5.64 ms in teenagers (p<0.001). Root mean square of the last 40 ms decreases with age, but remains stable after the age of 10 years (122.4 +/- 33.30 microV in infants, 60.9 +/- 31.27 in teenagers, p<0.001). QT dispersion, on the other hand, does not change significantly with age. The mean value for the whole group is 36 +/- 13.7 ms. A weak but significant correlation exists between QT dispersion and filtered QRS. Thus, age must be taken into consideration when interpreting signal-averaged electrocardiograms, but not when measuring QT dispersion.

Evaluation of myocardial ischemia in Kawasaki disease by dobutamine stress signal-averaged ventricular late potentials

OBJECTIVE

To determine the possibility of diagnosing myocardial ischemia from signal-averaged electrocardiographic late potentials (LPs) in patients with Kawasaki disease.

METHODS

Dobutamine stress LPs were obtained in 85 children with a history of Kawasaki disease (48 without coronary artery lesions, 19 with coronary artery lesions without myocardial ischemia, and 18 with myocardial ischemia). The infusion of dobutamine was started at 5 micrograms/kg/min, increased to 30 micrograms/kg/min. The presence of LPs was determined by the filtered QRS duration, the root mean square voltage during the last 40 ms, and the duration of the signal under 40 microV.

RESULTS

Among the children without coronary lesions, LPs were detected in 4.2% at rest and in 2.1% with dobutamine stress. Among the group with coronary lesions but without ischemia, LPs were found in 5.3% at rest and in 5.3% with stress. In the group with ischemia, LPs were present in 44.4% at rest and in 77.8% with stress. The sensitivity for myocardial ischemia was 72.7% at rest and 87.5% with stress (p < 0.05), and the specificity was 86.5% at rest and 94.2% with stress.

CONCLUSION

LPs associated with dobutamine stress testing are useful for identifying myocardial ischemia in children with Kawasaki disease, especially in those who cannot tolerate testing involving physical exercise.