Have you ever wondered what the secret to someone’s heart is? That's right, a chest x-ray! All right, so, here at Osmosis we don't actually have the secret to one’s heart, but we do know how to identify the different medical conditions that can affect the heart.
Let's start off by identifying the heart borders on a chest x-ray. The heart silhouette is between the lungs, and the right border, made up by the right atrium, as well as the left border, made up by the left ventricle and part of the left auricle, can be clearly seen. Above the left auricle, we can identify the pulmonary artery and the aortic arch. And in some clinical circumstances, the silhouette sign can be present, which is when the normal heart silhouette of the heart compared to the lungs is lost. More appropriately, you might want to think about it as a “loss of the heart silhouette”. The loss of the heart silhouette only occurs when the pathological process is in direct anatomical contact with the heart. Usually, the middle lobe is seen close to the right border of the heart. So, consolidation in the right middle lobe can also obscure the x-ray silhouette of the right heart border.
All right, now, even though the heart is protected by the sternum and thoracic cage, it’s still susceptible to injury. During penetrating trauma, like, for example, a stab wound, the right ventricle is the most commonly injured structure because of its anterior position in the chest and the fact that it forms the majority of the anterior surface of the heart, followed by the left ventricle which forms the apex of the heart and may be injured as far laterally as the left midclavicular line at the 5th intercostal space. The atria are less commonly injured than the ventricles. It’s also worth noting that the lungs overlap most of the anterior surface of the heart, so many penetrating injuries to the heart will also result in concurrent lung injury particularly to the parietal pleura.