Pectus excavatum can harm the patient's or child's heart, primarily manifesting in compression of the heart and affecting the function of the internal heart valves. Imagine a normal person's rib cage, which is oval in cross-section. There is a certain ratio between the lateral diameter and the anterior-posterior diameter, with normal individuals having a ratio of less than 2.5. However, in patients with pectus excavatum, this anterior-posterior diameter is significantly compressed, meaning the sternum moves closer to the spine, compressing inward and backward, squeezing the heart - this is the first step. The heart itself is a contractile muscular organ, its purpose being to eject blood and circulate it throughout the body. If the sternum and spine directly compress the heart, preventing it from fully expanding, then blood cannot fully flow back into the heart, and thus the ejection or pumping function of the heart will be impacted. Secondly, besides the heart being compressed, just like a house becoming deformed from being squeezed, the doors within the house cannot function properly; they cannot close or open well. Thus, pectus excavatum not only compresses the heart itself but also severely harms the function of the heart valves, even causing mitral valve prolapse in some patients.