Effects of isosorbide dinitrate on oxygen uptake kinetics in cardiac patients.
OBJECTIVE
Although nitrates are known to improve indices of exercise capacity in patients with coronary artery disease, their effects on oxygen uptake kinetics during the onset of exercise have not been clarified. We evaluated the acute effects of isosorbide dinitrate on the kinetics of oxygen uptake during the onset of exercise at a constant work rate in patients with coronary artery disease.


METHODS
We studied 14 patients with coronary artery disease who performed 6 min of low-intensity exercise at a constant work rate on a cycle ergometer 30 min after oral administration of 10 mg of isosorbide dinitrate or placebo in a double-blind, crossover manner. Oxygen uptake was calculated from breath-by-breath analysis of respired gases. The time constant of oxygen uptake kinetics during the onset of exercise was determined by fitting a single exponential function to the oxygen uptake response.


RESULTS
Heart rate was significantly increased at rest, and systolic blood pressure was significantly decreased both at rest and during exercise after administration of isosorbide dinitrate. The time constant of oxygen uptake was significantly shorter (the kinetics were faster) after administration of isosorbide dinitrate (39.4+/-10.1 vs 44.5+/-10.5 s, P = 0.038).


CONCLUSIONS
Isosorbide dinitrate was found to speed the kinetics of the increase in oxygen uptake during constant work-rate exercise. The time constant of oxygen uptake, which reflects the rapidity of cardiovascular adaptation at the onset of exercise, seems to be a useful parameter of the effectiveness of therapy in patients with coronary artery disease.
Koike
A
A
The Kasumigaura Branch Hospital, Tokyo Medical and Dental University, Ibaraki, Japan.
Yajima
T
T
Koyama
Y
Y
Shimizu
N
N
Kano
H
H
Kobayashi
K
K
Taniguchi
K
K
Marumo
F
F
Hiroe
M
M
D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D003327:Coronary Disease / Q000188:drug therapy* / Q000503:physiopathology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007548:Isosorbide Dinitrate / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects*; D014665:Vasodilator Agents / Q000627:therapeutic use*
D014665:Vasodilator Agents; D007548:Isosorbide Dinitrate