Table 4.

Hazard ratios of frequency and regularity to self-termination

Model	Variable	HR (95% CI)a
		Unadjusted model	Adjusted by pathology	Fully adjusted
Univariate	DF	0.969 (0.844–1.065)	0.971 (0.842–1.070)	0.966 (0.841–1.063)
	RI	0.952 (0.927–0.977)	0.952 (0.926–0.978)	0.953 (0.927–0.979)
Multivariate	DF	0.986 (0.861–1.082)	0.985 (0.859–1.049)	0.983 (0.857–1.047)
	RI	0.953 (0.928–0.978)	0.953 (0.927–0.979)	0.954 (0.928–0.980)

Univariate and multivariate models introduce DF and RI as time-dependent variables and report corresponding hazard ratios (HRs) for self-termination of PVT/VF episodes. The time variables DFs and RIs are for the entire duration of each episode and for all the episodes. The univariate (DF or IR) and multivariate (DF and RI) models analyze the HR for 0.1 Hz DF and 0.01 RI changes. Models are tested unadjusted, adjusted by type of pathology, or fully adjusted by type of pathology and controlling variables of age at the first PVT/VF episode, sex, existence of prior documented congestive heart failure, width of the QRS and LV ejection fraction at the time of the ICD implantation. HR, hazard ratio; 95% CI, 95% confidence interval; DF, dominant frequency; RI, regularity index. ^a95% CI based on 10 000 iterations of the general bootstrap algorithm.