Page 19, O2 Uptake, Exercise & Cor. Circ., Dr. D. Penney

Coronary Circulation (continued..):

A number of factors influence the ability of the coronary circulation to deliver oxygen: Coronary blood flow (CBF) as determined by vascular resistance, arterial pressure minus tissue pressure, vasodilator reserve and the presence of collaterals are major factors. Others variables are the kind and amount of hemoglobin present (variant due to genetic disease, methemoglobin, carboxyhemoglobin), shape of the ODC (right- or left-shifted), alveolar PO2, amount of cardiac myoglobin, average capillary to mitochondrial diffusion distance (increased by hypertrophy), capillary density, and erythrocyte deformability (e.g. sickle cells don't deform easily) and blood rheology. Coronary capillaries at a diameter of 4.5 um are among the smallest in the body. Erythrocytes being about 8 um in diameter must grossly deform in order to pass through them.

Coronary perfusion is determined diagnostically in order to detect coronary artery disease. This can be done using the Thallium scan.