Table 1.

Demographic Data for Three Impedance Groups

	Mean Measured Impedance between 6 and 9 months
	Group L	Group M	Group H
	27 – 65 Ω	66 – 72 Ω	73 – 170 Ω
	(n=48709)	(n=46933)	(n=50596)
Age at implant, years	70 ± 12	68 ± 11	65 ± 11	p < 0.001
Gender
Female	29%	22%	24%
Male	71%	78%	76%	p < 0.001
Device type
ICD-VR	12%	14%	18%
ICD-DR	38%	41%	41%
CRT-D	50%	45%	41%	p < 0.001
Mean follow-up, months	26 ± 18	29 ± 19	32 ± 20	p < 0.001
Status
Alive	82%	86%	87%
Dead	18%	14%	13%	p < 0.001

Abbreviations: Ω = Impedance in ohms, group L = patients with baseline measured impedance ≤ 65 ohms, Group M = patients with baseline measured impedance 66–72 ohms; Group H: patients with baseline measured impedance ≥ 73 ohms. ICD-VR = single chamber intra-cardiac defibrillator, ICD-DR = dual chamber intra-cardiac defibrillator, CRT-D = cardiac resynchronization with an cardiac defibrillator.