{'fraction_non_alphanumeric': 0.008382229673093043, 'fraction_numerical': 0.0, 'mean_word_length': 6.325153374233129, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Innate collateral segments are predominantly present in the subendocardium without preferential connectivity within the left ventricular wall

Innate collateral arteries provide the biophysical substrate for arteriogenesis. Their distribution and morphology predestine tissue areas salvageable by collateral flow. Fluorescent episcopic cryomicrotome imaging resulted in a three‐dimensional representation of the coronary network, in which collateral segments were automatically identified. Innate collateral segments are predominantly present in the subendocardium without preferential connectivity within the left ventricular wall of the dog heart and are preferentially oriented perpendicular to the long axis of the heart in the outer layers and parallel to this axis at the subendocardium. These results suggest that collateral segments are maintained without local hypoxia but because of heterogeneity in pressure gradients in the arterial tree. The high density and long‐axis orientation of collateral arteries in the subendocardial region provide the substrate for arterial plexus formation and indicate the need for three‐dimensional perfusion assessment in clinical perfusion imaging.