Does age affect intrinsic heart rate, heart rate variability, and AV conduction in healthy humans before and after autonomic blockade?
Age-related differences in heart rate and AV conduction persist independently of autonomic influences, whereas differences in heart rate variability are largely explained by autonomic tone.
Heart rate, heart rate variability, and atrioventricular (AV) conduction were studied in 20 young (30 +/- 5 yr) and 19 older (69 +/- 7 yr) healthy men and women before and after single and double autonomic blockade (randomized order: atropine, 0.04 mg/kg i.v.; propranolol, 0.2 mg/kg i.v.). Basal R-R intervals did not differ, but older age increased P-R intervals (177 +/- 24 vs. 149 +/- 17 ms, P 98%, P < 0.0001). We conclude that age differences in heart rate variability can be explained by autonomic influences, but heart rate and AV conduction differences exist independently of beta-adrenergic and/or parasympathetic influences.
Craft et al. (Sat,) studied this question.