Final answer:
Blood flows from higher to lower pressure through a septal defect; in heart chambers, this can cause mixing of blood and lead to conditions like Tetralogy of Fallot, detectable by auscultation.
Step-by-step explanation:
When not accompanied by other abnormalities, pressure differences will usually cause blood to flow from the higher pressure to the lower pressure through a septal defect. In the context of the heart and its chambers, this means that if a septal defect exists between two heart chambers, the blood will flow from the chamber with higher pressure to the one with lower pressure. Since oxygenated blood is in the left side of the heart and has a higher pressure compared to the deoxygenated blood in the right side, a septal defect such as in the condition called Tetralogy of Fallot can cause oxygen-rich blood from the left ventricle to mix with the oxygen-poor blood in the right ventricle. This mixing can lead to cyanosis and other symptoms mentioned. It's worth noting that septal defects can be detected by unusual heart sounds through auscultation and confirmed with medical imaging.