The collateral coronary circulation in the human fetus: angiographic findings.

Collateral circulation was studied in the heart of 20 normal human fetuses aged 19 to 39 weeks, using a radiographic technique. The radiograms showed the presence of coronary anastomoses ranging in size from 3 to 50 mu. The anastomoses were more abundant and of larger diameter in the interventricular septum and in the subendocardial layers. Anastomoses between the superficial vessels were also present but were less frequent and of smaller diameter.