Circulation, Vol 64, 1135-1141, Copyright © 1981 by American Heart Association
MF Shiu, MA Ireland and WA Littler
Prenalterol, a beta-adrenergic agonist, was given to nine patients with
angiographically proved coronary artery disease. Subjects were studied
during chronic beta-adrenergic blockade. The adequacy of blockade was
assessed by the exercise heart rate response and by plasma concentrations
of blocking agents. After incremental doses of 2.5 mg, 5.0 mg and 7.5 mg of
prenalterol, heart rate was increased by 20%, 24% and 38%, respectively,
and left ventricular dP/dt max by 55%, 73% and 61%, respectively. Systolic
and diastolic blood pressures did not change significantly; pulmonary
artery wedge pressure fell from 10 +/- 0.5 mm Hg to 7.1 +/- 0.9 and 6.7 +/-
0.7 mm Hg after 2.5 mg and 5.0 mg, respectively (p less than 0.01 for
both). The net inotropic response to prenalterol was assessed, independent
of the chronotropic response, using incremental atrial pacing before and
after drug infusion. At identical heart rates, left ventricular dP/dt max
increased by 40%, 49% and 48% after 2.5 mg, 5.0 mg and 7.5 mg,
respectively. Left ventricular cineangiography before and after infusion
showed an increase in ejection fraction from 0.73 +/- 0.02 to 0.83 +/- 0.03
(p less than 0.001). Plasma prenalterol concentration estimations
demonstrated a clear, dose-related inotropic response, the level of
response in each patient being largely determined by the degree of
beta-adrenergic blockade at the time of the study.
ARTICLES
Hemodynamic effects of atrial pacing and prenalterol infusion in patients taking beta-adrenergic blocking drugs