Effects of digoxin and enalapril on heart period variability and response to head-up tilt in normal subjects.
To test the effects of digitalis and angiotensin-converting enzyme inhibition on the RR interval variability in an electrocardiogram, 20 normal subjects were given digoxin 0.25 mg, enalapril 10 mg, and placebo twice daily in a randomized, double-blind, crossover study. Continuous 24-hour electrocardiographic recordings obtained on day 5 of each treatment were analyzed and several time domain and power spectral measures of heart period variability were calculated. Digoxin markedly increased (up to 51%) indexes of vagal modulation of heart period without changing mean RR interval. Enalapril did not change any measure of heart period variability despite a modest hypotensive effect. To determine the effect of each treatment on the response to orthostatic stress, 10 subjects also underwent 15 minutes of 60 degrees head-up tilt; power spectra were calculated for 15 minutes at 0 degree and at 60 degrees of tilt. Neither active treatment affected the response to head-up tilt.
Department of Medicine, School of Public Health, Columbia University, New York, New York.
E S
ES
Kaufman
M S
MS
Bosner
J T
JT
Bigger
P K
PK
Stein
R E
RE
Kleiger
L M
LM
Rolnitzky
R C
RC
Steinman
J L
JL
Fleiss
D000328:Adult; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology; D002940:Circadian Rhythm; D004077:Digoxin / Q000494:pharmacology*; D004311:Double-Blind Method; D015716:Electrocardiography, Ambulatory / Q000187:drug effects; D004656:Enalapril / Q000494:pharmacology*; D005260:Female; D006257:Head; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology
D004656:Enalapril; D004077:Digoxin