Final answer:
A post-MI ruptured interventricular septum leads to the mixing of oxygen-rich and oxygen-poor blood, resulting in decreased blood oxygen saturation and symptoms like dyspnea and cyanosis. Surgical repair is often required to fix the septum and restore proper blood oxygenation.
Step-by-step explanation:
A post-MI ruptured interventricular septum has a significant effect on blood oxygenation. The interventricular septum separates the left and right ventricles and is normally intact, preventing mixing of oxygen-rich blood from the left ventricle with oxygen-poor blood from the right ventricle. When a myocardial infarction (MI) leads to a rupture in this septum, oxygen-poor blood from the right ventricle can enter the left ventricle and mix with the oxygen-rich blood. This results in reduced oxygen saturation of the blood that is pumped throughout the body, leading to symptoms such as dyspnea and cyanosis. Treatment often involves surgical repair to correct the defect and prevent further complications. In the context of Tetralogy of Fallot, a congenital condition, an opening in the interventricular septum allows for a similar mixing of blood, leading to a decrease in oxygen saturation. Long-term changes in lifestyle in addition to medical or surgical treatments are required to manage the condition effectively.