Follow-Up and Risk Assessment in Patients with Myocardial Infarction Using Artificial Neural Networks

Table 2

Association of risk variables with cardiac mortality in univariable analysis.

Method	Variable (values)	Hazard ratio, 95% CI (univariable)
ECG parameters	QT interval (≤378)	1.38 (1.08–1.76)	0.009
	QTc interval (>434)	1.28 (1.00–1.67)	0.050
	PR interval (151–184)	0.69 (0.52–0.91)	0.008
	QRS complex (≤87)	0.56 (0.42–0.75)	0.001
	P wave (64.19–72.36)	2.14 (1.06–4.34)	0.034
Time domain analysis	Average HR (>84.7)	1.73 (1.05–2.86)	0.032
	SDNN (≤120.0)	9.33 (1.31–66.7)	0.026
	RMSSD (>53.7)	1.58 (1.04–2.40)	0.030
	pNN50 (≤2.7)	8.84 (1.14–68.56)	0.037
HRV statistics	VLF-RRI (351.4–406.2)	3.68 (1.06–12.84)	0.041
	PSD-RRI (≤276.5)	2.55 (1.02–6.35)	0.044

SDNN: standard deviation of all the RR intervals; RMSSD: square root of the mean of squared differences of two consecutive RR intervals; pNN50: percent of beats with consecutive RR interval difference of more than 50 milliseconds; VLF: very low frequency component of HRV; PSD: total power of HRV; HRV: heart rate variability; ECG: electrocardiogram.