Differential anti-ischaemic effects of muscarinic receptor blockade in patients with obstructive coronary artery disease - impaired vs normal left ventricular function

Aims In patients with coronary artery disease acetylcholine (a muscarinic agonist) causes vasoconstriction. The effect of atropine (a muscarinic antagonist) on coronary vasotone in patients with normal or impaired left ventricular function is unknown.

Methods and Results Twenty-four patients who required atropine infusion (to supplement heart rate response) during atrial pacing (pacing was conducted to assess ischaemia as part of an experimental protocol) were studied; 17 patients had normal and seven impaired left ventricular function (ejection fraction less than or equal to 0.40). Two control groups were selected from a large database (from patients in whom atrial pacing was carried out but to whom atropine was not administered) to match the normal (n = 20) and dysfunction (n = 10) groups. In the normal left ventricular function group atropine increased rate pressure product by 12 +/- 4%, as compared to those without atropine (P

Conclusion In patients with normal left ventricular function atropine improves coronary flow and reduces myocardial lactate production and ST-segment depression during atrial pacing, suggesting a reduction in myocardial ischaemia. (C) 1999 European Society of Cardiology.