Everyone knows where the heart is located. Therefore, when pain occurs in the left sternum, practically no one asks what it is, since the answer is ready in advance - it is the heart. But is it always like that?
In order to understand what causes pain in the sternum on the left, you need to know what is there. In addition to the heart, in this area is the left main bronchus, which enters the left lung, and its membrane, rich in nerve endings. Also there is a part of the mediastinum along which the nerves, large vessels, for example, the aorta pass. In addition to the heart, there is also its shell, called the pericardium, also rich in nerve endings. Do not forget about the chest, as nerves and blood vessels pass between the ribs, and the ribs are supported by intercostal muscles.
The most common diseases that people die from are related to heart disease. Basically, these are diseases caused by heart failure, such as various arrhythmias, angina pectoris, myocardial infarction, as well as myocarditis, pericarditis, endocarditis (but this is less common than the above diseases). All these pathologies can cause pain in the sternum on the left, but the pain in each disease is different from each other. For example, with angina pectoris, the pain has a compressive character and can be given to the left hand or to the left side of the neck, sometimes a feeling of numbness in the hand appears. The duration of pain in the left sternum does not exceed 15 to 20 minutes and it passes very quickly after taking nitroglycerin. With a heart attack, the pain is located in the sternum on the left (but not always), but it is much stronger, sometimes reaching the shock of cardiac etiology. The patient may lose consciousness, the temperature may rise, there is severe sweating, the pain also gives to the left arm, the left side of the neck and face. Such pain is not stopped by nitroglycerin, but needs strong analgesics and highly qualified help. But sometimes a heart attack, especially in older people, is manifested by much less symptomatology, less acute pain, and sometimes it even goes away asymptomatically.
With pericarditis, pain appears depending on the rate of progression of the disease. Serous pericarditis is characterized by the accumulation of fluid in the space between the membranes of the pericardium, if this accumulation is slow, then there may not be pain, or it is initially insignificant and increases along with the progression of the disease. The amount of liquid can reach 1 - 1.5 liters and even more. But if pericarditis appears spontaneously, as, for example, in cardiac tamponade, then the pain in the sternum on the left is acute, unbearable, does not go away after nitroglycerin.
Pulmonary disease can also be a pain in the left sternum. This refers to the left lung and its main bronchus. The bronchus can be ill with acute bronchitis with a severe course, also a tumor or some foreign body can be located there, which is very rare. The lungs give pain in pneumonia (pneumonia) when the pleura (pulmonary membrane) is introduced into the inflammatory process, since the lungs do not have nerve endings and cannot hurt on their own, and the pleura is rich in them. In this case, the pain is located on the affected side, it increases with inspiration and is practically absent during respiratory arrest, so the patient tries to breathe on the opposite side. Among other diseases, there may be a tumor, tuberculosis, but the pain in the sternum on the left will appear in cases where bronchi or pleura are introduced into the process. There are a number of diseases associated with pleura: pneumothorax (air entering the pleural cavity), pleurisy of various etiologies (the intensity of pain appears, as with pericarditis), empyema, etc. It should be remembered that pain in diseases of the lungs and pleura depends on the breathing process.
Very often, especially adolescents complain of acute pain in the sternum on the left, which is often associated with the inability to inhale. This scares many, suggesting that this is some kind of heart disease, but in fact very often it is intercostal neuralgia, which appears during stress, long tension, or an incorrect position of the spine. This pain does not last long, often goes away on its own, after a massage in this area or after sedatives. Sometimes the cause may be osteochondrosis in the thoracic spine. In such cases, more attention should be paid to this.
As you already noticed, there are a lot of reasons for pain in the sternum on the left, and this is not the whole list of diseases. In any case, in order to find out the exact cause, you should consult a doctor to prevent serious consequences.