Age-related changes of sinus node function and autonomic regulation in subjects without sinus node disease--assessment by pharmacologic autonomic blockade.
To assess the relationship between aging and autonomic regulation of sinus node function, 56 subjects of various ages (range 14-75 years, mean 43 +/- 19 years) without sinus node disease were studied. Heart rate, corrected sinus node recovery time and sinoatrial conduction time were measured before (basic) and after (intrinsic) pharmacologic autonomic blockade (propranolol + atropine i.v.). Percent chronotropies of the above parameters were calculated by a modified Jordan's method. Basic heart rate and basic corrected sinus node recovery time did not vary with age (r = -0.15, r = 0.08, respectively), while basic sinoatrial conduction time tended to increase with age (r = 0.32, p < 0.05). Intrinsic heart rate decreased (r = -0.76, p < 0.001), and intrinsic corrected sinus node recovery time and intrinsic sinoatrial conduction time both increased with age (r = 0.55, p < 0.001; r = 0.56, p < 0.001, respectively). The younger the subject, the more negative the percent chronotropies of the above parameters were, and the percent chronotropies correlated positively with age (r = 0.68, p < 0.001; r = 0.52, p < 0.001 and r = 0.34, p < 0.05, respectively). In conclusion, intrinsic sinus node functions deteriorated with age. Furthermore, parasympathetic tone on the sinus node functions decreased with age, which may compensate for age-related deterioration of intrinsic sinus node function.
Kuga
K
K
Department of Internal Medicine, University of Tsukuba, Ibaraki, Japan.
Yamaguchi
I
I
Sugishita
Y
Y
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001285:Atropine; D001340:Autonomic Nerve Block; D001341:Autonomic Nervous System / Q000502:physiology*; D004594:Electrophysiology; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011433:Propranolol; D012044:Regression Analysis; D012849:Sinoatrial Node / Q000294:innervation / Q000502:physiology*
D001285:Atropine; D011433:Propranolol