Rfe. Pedretti et al., EFFECTS OF ORAL PIRENZEPINE ON HEART-RATE-VARIABILITY AND BARORECEPTOR REFLEX SENSITIVITY AFTER ACUTE MYOCARDIAL-INFARCTION, Journal of the American College of Cardiology, 25(4), 1995, pp. 915-921
Objectives. Our aims were 1) to assess whether oral pirenzepine could
increase indexes of cardiac vagal activity in postinfarction patients,
and 2) to compare the effects of this agent with those of transdermal
scopolamine. Background. Depression of vagal tone and reflexes predic
ts a poor arrhythmic outcome after myocardial infarction, Intervention
s for shifting the sympathovagal balance toward vagal dominance are no
w of increased clinical interest. Intravenous pirenzepine increases RR
interval variability in normal volunteers, a finding that could have
therapeutic implications if confirmed in postinfarction patients after
oral administration of the drug. Methods. In a single-blind placebo-c
ontrolled crossover trial, short-term RR interval variability and baro
receptor reflex sensitivity were evaluated in 20 patients an average o
f 19 +/- 6 days after infarction. Analysis was performed during contro
l conditions and during administration of placebo, oral pirenzepine an
d transdermal scopolamine. Results. Compared with placebo, at a dose o
f 25 mg mice daily, pirenzepine significantly increased all time and f
requency domain measures of RR interval variability and augmented baro
receptor reflex sensitivity by 60% (mean +/- 1 SD 10.4 +/- 5.9 vs. 6.5
+/- 3.2 ms/mm Hg, p = 0.0007). Pirenzepine and scopolamine shelved a
similar vagomimetic effect, but the overall incidence of adverse effec
ts was lower with pirenzepine (1 [5%] of 20 vs. 10 [50%] of 20). Concl
usions. In patients with a recent myocardial infarction, oral pirenzep
ine proved equal to transdermal scopolamine in significantly increasin
g indexes of cardiac vagal activity. These data suggest that oral pire
nzepine may have a therapeutic potential for preventing malignant vent
ricular arrhythmias after infarction.