H. Krum et al., EFFECT OF LONG-TERM DIGOXIN THERAPY ON AUTONOMIC FUNCTION IN PATIENTSWITH CHRONIC HEART-FAILURE, Journal of the American College of Cardiology, 25(2), 1995, pp. 289-294
Objectives. This study was conducted to determine the effect of long-t
erm digoxin therapy on autonomic function in patients with mild to mod
erate chronic heart failure. Background. Chronic heart failure is char
acterized by increased sympathetic activity and decreased parasympathe
tic activity. Intravenous digitalis has been found to reduce sympathet
ic activity immediately in these patients, but whether short-term neur
ohormonal effects are sustained during long-term oral therapy has not
been assessed. Methods. We determined sympathetic activity in 26 patie
nts with heart failure by measuring plasma norepinephrine levels and p
arasympathetic activity from variables of heart period variability der
ived from 24-h ambulatory electrocardiographic Holter recordings obtai
ned before and after 4 to 8 weeks of digoxin therapy. Results. After d
igoxin therapy, plasma norepinephrine decreased significantly from a m
ean +/- SEM of 552 +/- 80 to 390 +/- 37 ng/ml. In addition, the RR int
erval increased significantly from 719 +/- 19 to 771 +/- 20 ms. High f
requency power increased from 84 +/- 24 to 212 +/- 72 ms(2), and the r
oot mean square of successive differences in RR interval increased fro
m 20.3 +/- 1.8 to 27.0 +/- 3.4 ms, indicating a substantial increase i
n parasympathetic activity. Low frequency power, an index of barorefle
x activity, was also significantly increased (239 +/- 80 to 483 +/- 14
4 ms(2)) by digoxin therapy. Conclusions. These results indicate 1) th
at long-term therapy with digoxin acts to ameliorate the autonomic dys
function of patients with heart failure, and 2) that the short-term ne
urohormonal effects of digoxin are sustained during prolonged treatmen
t with the drug.