Effect of nicotine on coronary blood-flow in man

Summary. The effect of 4 mg nicotine administered in a chewing gum on coronary haemodynamics and oxygen transport, was studied by coronary sinus catheterization in eight healthy non-smoking men. Measurements were made of coronary sinus blood-flow (CSF) by thermodilution and arterial-coronary sinus (a-cs) O₂-difference together with heart rate and intra-arterial pressure both at rest, and during, atrial pacing with and without nicotine. Nicotine increased myocardial oxygen consumption (MVO₂) more than expected from the increase in the rate-pressure product. The increased MVO₂ was covered only partly by increased coronary blood-flow; especially during and after pacing an increased a-cs O₂-difference contributed significantly. This differed from the response when MVO₂ was increased by atrial pacing alone, in which case the whole increase in MVO₂ was covered by increased flow. The results suggest that nicotine affects coronary vascular resistance and blood-flow indirectly through a vasodilatory effect, by mechanisms related to the increased cardiac work, and directly through a vasoconstrictory effect. The suggested vasoconstrictor component is moderate in the non-ischaemic human heart.