Table 2.

Results of Longitudinal Multilevel Linear Regression

Heart Rate Variability Measures	Baseline Values			Changes Over Time for NCI+
	Beta	Standard Error	p-value	Beta	Standard Error	p-value
MNN	−0.10	0.018	<0.0001	0.00015	0.000016	<0.0001
SDNN	−0.016	0.0045	0.0003	0.0000053	0.0000025	0.0354
CV	−0.102	0.018	<0.0001	0.00028	0.000011	<0.0001
RMSSD	−0.016	0.005	0.0022	−0.00001	0.0000029	<0.0001
SD1	−0.010	0.004	0.0194	0.0000094	0.0000017	<0.0001
SD2	−0.020	0.0048	<0.0001	0.0000028	0.0000033	0.4013
SD Ratio	0.079	0.031	0.0103	−0.00010	0.000030	0.0007
HFP	−0.221	0.119	0.0646	0.00036	0.00012	<0.0001
LFP	−0.185	0.233	0.4271	−0.0013	0.00029	0.0035
LHR	3.42	0.92	0.0002	−0.015	0.0011	<0.0001
DFA Alpha 1	−0.049	0.031	0.1132	0.0000061	0.000032	0.0560
DFA Alpha 2	0.0867	0.019	<0.0001	−0.00003	0.000043	0.4936

NCI = neurocardiogenic injury; MNN = mean of normal RR intervals; SDNN = mean of the standard deviations for all normal to normal RR intervals; CV = coefficient of variation of the RR interval time series; RMSSD = square root of the mean squared differences of successive NN intervals; SD1 = quantitative interpretation of Poincare plot and the standard deviation of the minor axis; SD2 = quantitative interpretation of Poincare plot and the standard deviation of the major axis; SD Ratio = SD1/SD2; HFP = high frequency power; LFP = low frequency power; LHR = LFP/HFP; DFA = detrended fluctuation analysis. For explanations of these terms, see Appendix B and C.