Effects of short-term aminophylline administration on cardiac functional reserve in patients with syndrome X.
OBJECTIVE
This study sought to evaluate the effect of adenosine receptor blockade by aminophylline on cardiac functional reserve in patients with syndrome X.


BACKGROUND
Aminophylline may have a potentially antiischemic effect through the inhibition of adenosine and, thus, the coronary steal phenomenon in patients with syndrome X.


METHODS
A single-blind, placebo-controlled study of an intravenous infusion of aminophylline (6 mg/kg body weight over 15 min) or placebo (20 ml of saline solution over 15 min) was performed during continuous radionuclide monitoring of left ventricular ejection fraction in 12 patients performing supine bicycle ergometric exercise.


RESULTS
Aminophylline increased exercise time (aminophylline 400 s vs. placebo 355 s, p < 0.01), decreased degree of ST segment depression (aminophylline 1.6 mm vs. placebo 2.4 mm, p < 0.01) and either abolished (seven patients) or diminished (five patients) chest pain during exercise. Aminophylline also increased left ventricular ejection fraction at rest (aminophylline 66.5% vs. placebo 62.3%, p < 0.05) but did not improve its deterioration at peak exercise (aminophylline 60.1% vs. placebo 56.6%, p = NS) or shorten the abnormally prolonged interval between the end of exercise and the overshoot (aminophylline 115 s vs. placebo 130 s, p = NS).


CONCLUSIONS
Aminophylline infusion increases ischemic threshold and prolongs exercise duration in patients with syndrome X. It is hypothesized that aminophylline acts by inhibiting the coronary steal phenomenon through adenosine receptor blockade. It does not improve the deterioration in left ventricular function at peak exercise or the delayed response in ejection fraction in the recovery period, presumably because the beneficial effects of aminophylline that result from the redistribution of coronary blood flow are limited.
Yoshio
H
H
Second Department of Internal Medicine and Nuclear Medicine, School of Medicine, Kanazawa University, Japan.
Shimizu
M
M
Kita
Y
Y
Ino
H
H
Kaku
B
B
Taki
J
J
Takeda
R
R
D000628:Aminophylline / Q000008:administration & dosage / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects*; D018592:Cross-Over Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D017566:Microvascular Angina / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008875:Middle Aged; D015635:Radionuclide Ventriculography / Q000295:instrumentation; D018047:Receptors, Purinergic P1 / Q000187:drug effects*; D016037:Single-Blind Method; D013318:Stroke Volume / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects*
D018047:Receptors, Purinergic P1; D000628:Aminophylline