Abstract

Glyceryl trinitrate is the best drug for preventing anginal pain.¹ It is often assumed to dilate coronary arteries, but measurements of myocardial blood flow in man have failed to show that sublingual administration of the drug increases flow in patients with diseased coronary arteries.² Local accumulation of metabolites during angina is believed to cause coronary vasodilatation: whether any drug can cause further local vasodilatation is uncertain. However, dilatation of the vascular bed may occur when the drug is injected into the coronary arteries of patients with ischaemic heart disease.³ The drug lowers arterial pressure both at rest and during exercise and it diminishes cardiac oxygen consumption. Thus it may help by reducing the metabolic requirements of the heart.¹