Table III.

Summary of serial measurements on ECGs

Measurement	Admission	P value	Midpoint	P value	Discharge	P value	Follow-up
Number of patients	63		55		60		60
ECG parameters:
Heart rate (bpm)	108 ± 22	<.001	80 ± 22	.171	77 ± 20	<.001	88 ± 15
PR interval (msec)	136 ± 24	.023	146 ± 28	.295	142 ± 26	.013	133 ± 18
QRS duration (msec)	84 ± 12	.374	88 ± 13	.048	84 ± 10	.376	84 ± 11
QRS axis (degrees)	71 ± 36	.014	63 ± 35	.596	64 ± 32	.004	57 ± 28
QTc (msec)	410 ± 30	.909	412 ± 29	.019	401 ± 25	.720	403 ± 22
Conduction/repolarization delay:
First degree AV block, number (% of children)	5 (8%)	n/a	9 (17%)	n/a	7 (12%)	n/a	2 (3%)
QRS prolongation, number (% of children)	4 (6%)	n/a	4 (7%)	n/a	1 (2%)	n/a	0
QTc prolongation, number (% of children)	7 (11%)	n/a	8 (15%)	n/a	2 (3%)	n/a	1 (2%)
QRS amplitude (mV):
R wave V1	0.473 ± 0.44	.789	0.469 ± 0.39	.104	0.555 ± 0.45	.086	0.686 ± 0.44
S wave V1	0.761 ± 0.59	0.390	0.789 ± 0.53	.169	0.917 ± 0.62	<.001	1.231 ± 0.64
R wave V4	1.663 ± 0.84	0.841	1.603 ± 0.81	.381	1.728 ± 0.74	.022	2.080 ± 0.78
R wave V6	1.296 ± 0.50	0.166	1.410 ± 0.55	.222	1.523 ± 0.60	.564	1.629 ± 0.46
T-wave amplitude (mV):
T wave amplitude (mV) Lead I	0.197 ± 0.14	0.153	0.233 ± 0.16	.909	0.240 ± 0.16	<.001	0.347 ± 0.12
T wave amplitude (mV) V6	0.214 ± 0.13	0.214	0.243 ± 0.20	.071	0.297 ± 0.17	<.001	0.436 ± 0.12
T/R ratio V6	0.175 ± 0.10	0.502	0.188 ± 0.14	.116	0.212 ± 0.13	<.001	0.280 ± 0.08
T-wave changes:
Number negative T-waves in chest leads	1.52 ± 1.36	0.181	1.75 ± 1.61	.010	1.23 ± 1.20	.054	0.95 ± 0.86
TWI present in V4-6, number (% of children)	7 (11%)	n/a	9 (16%)	n/a	3 (5%)	n/a	1 (2%)

n/a, not applicable.

Values are given as mean ± SD, or number (percentage). P values are comparisons between time points represented in adjacent columns.

P values are represented in bold if statistically significant (P < .05).