“…Coronary circulation normally responds to increased myocardial oxygen demand with an increase of coronary flow. Different methods have been used in experimental animals and in man to increase oxygen demand of the myocardium, for example exercise (2, 6, 12,14), isoprenaline infusion or other pharmacological agents (2, 26), and pacing-induced tachycardia (PIT) (3, 4, 7, 8,9,16,20,23,24). 1 Present address: Afd.…”