Table 3.

Correlations between HRV indices in ICD patients.

	RMSSD	PNN50	SDNN	HF-HRV	LF-HRV	LF/HF
PNN50	0.89 **
SDNN	0.60 **	0.56 **
HF-HRV	0.64 **	0.58 **	0.70 **
LF-HRV	0.53 **	0.43 *	0.75 **	0.82 **
LF/HF	−0.34 *	−0.35 *	−0.10	−0.43 **	0.13
HR (avg)	−.275	−.275	−.502 **	−.305 *	−.207	.214

RMSSD = root mean square successive difference of RR intervals; PNN50 = percent of successive RR interval differences > 50 ms; SDNN = standard deviation of RR intervals (SDNN); LF = low frequency HRV; HF = high frequency HRV; LF/HF = ratio of LF and HF; HR (avg) = Average heart rate during ambulatory monitoring.