[Studies on the degree of hypoxic and pharmacological coronary dilation (author's transl)]

On 11 isolated dog hearts, perfused with arterial blood of a donor dog, the degree of hypoxic dilatation and the maximum coronary blood flow achieved by adenosine were compared. The maximum coronary blood flow under adenosine infusion amounted to 455ml/minx100g, that means an increase of about 600% of the normal flow. If coronary venous pO2 was below 5mm Hg coronary blood flow was increased to 420ml/minx100g, which is 93% of the pharmacologically achieved maximum increase of the coronary blood flow. The difference between the maximum hypoxic and the maximum pharmacological dilatation is due to the method; it is caused by an increase of the extravascular component of coronary resistance under the influence of catecholamines in the case of hypoxic dilatation. It is pointed out that in order to achieve a maximum hypoxic dilatation oxygen pressure has to be below the critical value. It can be concluded that the intravascular component of coronary resistance is as low under hypoxic as under pharmacological dilatation.