People are often accustomed to thinking in conventional ways, which creates a kind of inertia. As the name implies, this is a habitual long-term cultivation of the way of thinking. If we talk about the abstract, the object has the nature of maintaining the original state of motion unchanged is called inertia. If we talk about inertia more concretely, inertia is a line of fifty sheep jumping over the fence, the first forty-nine have jumped, the fence will be removed, and the last sheep will follow the previous sheep to do the same jumping action. In fact, many misdiagnoses in clinical work are related to mis-treatment cases and inertia, and the theory and knowledge will be introduced below. Straight-back syndrome is also known as pseudo-heart disease, flat chest syndrome, and straight-back-flat chest syndrome. It was first reported by Rawlings in 1960. It is characterized by the loss of thoracic curvature, shortening of the anterior and posterior thoracic diameters, cardiac murmurs and abnormal X-rays due to compression of the heart and large blood vessels. Because clinicians do not pay enough attention to this syndrome and know less about it, the inertial way of thinking is easy to act, so it is often misdiagnosed in clinical practice. Five cases of straight back syndrome misdiagnosis of heart disease are analyzed as follows. Straight back syndrome is an autosomal dominant disorder with a family history. It is mainly associated with congenital malformation or some unexplained spinal developmental disorder or abnormal rib curvature in early childhood. It can also be due to abnormal development of the vertebral body during the embryonic period. Clinical manifestations may include dizziness, insomnia, chest tightness, palpitations and other non-cardiac-specific symptoms, or may be asymptomatic and found only during physical examination. As the thoracic vertebrae are straightened, the sternum is flattened vertically and nearly parallel to the spine, so the successive diameter of the thorax becomes smaller, the heart and large blood vessels are compressed by the sternum and spine, resulting in deformation and distortion, and when the heart contracts, the blood flow changes from laminar flow to vortex and produces jet murmur, the second heart sound of the pulmonary artery is hyperactive or even split, and the murmur is reduced when sitting and inspiration. Diagnosis is mainly based on: 1. Long and lean body shape, flattened thorax, and interscapular depression. A grade 2-4/6 systolic jet murmur is heard in the pulmonary valve region, without tremor, and P2 is hyperactive or split. The systolic murmur may appear in the apical region or at the base of the heart. 2.X-ray performance has characteristic diagnostic value. The lateral chest radiograph shows the disappearance of normal physiological posterior convexity of the thoracic spine, flattening or shortening of the anterior-posterior diameter, the ratio of anterior-posterior diameter/transverse diameter is less than 0.42 or the ratio of transverse diameter/anterior-posterior diameter is greater than 2.5. The orthopantomogram shows normal blood in both lungs, a typical “pancake-like” enlargement of the heart and lungs, leftward and forward displacement and left-posterior rotation of the great vessels of the heart, the pulmonary artery trunk The pulmonary artery trunk was “bulging” and the aorta was shifted to the midline. Narrowing or occlusion of the anterior and posterior cardiac space. 3, Mild clinical symptoms are not compatible with a loud heart murmur. 4. There are no specific findings on electrocardiogram and echocardiogram, and no hemodynamic changes on cardiac catheterization. This sign is most likely to be misdiagnosed as congenital heart disease, such as atrial and ventricular septal defect, pulmonary valve stenosis, etc. There are also cases of misdiagnosis as wind heart disease, myocarditis, hyperthyroidism, anemia and pulmonary disease. However, careful physical examination and targeted ancillary tests can help to make the distinction. The main reasons for misdiagnosis are: 1. Inertial thinking pattern, narrow thinking, limited to the diagnosis of common and multiple diseases. Patients visit the clinic for cardiac symptoms, but clinicians limit their consideration to cardiac disorders and ignore non-cardiac factors, leading to misdiagnosis. 2. Blindly believe in previous diagnosis without independent opinion. For cases with poor treatment results, they do not actively pursue the root of the problem and follow the clouds. 3. Neglecting the lateral chest x-ray examination. The prognosis of this sign is good, and no special treatment is needed because it does not affect the function. With the increase of age, the development gradually tends to be perfect, and the elasticity of lung tissue and thorax decreases. With the widening of the anterior and posterior diameter of the thorax, the compression of the heart and large blood vessels can be partially or completely relieved, and there is a tendency of natural relief. However, for those who have no obvious tendency to remission with age, pulmonary diseases should be prevented. Minimize the cardiac load to prevent the occurrence of chronic obstructive pulmonary disease and heart failure.