Retrosternal pain that worsens on deep inspiration is pleuritic-type chest pain. It can occur with relatively minor causes such as chest-wall muscle/rib irritation or pleurisy, but it can also occur with pericarditis, pneumonia, pneumothorax, or a pulmonary embolism. Pericarditis can cause sharp central pain that is worse on deep breathing or lying down, while pulmonary embolism may cause pain with breathlessness, a fast heart rate, coughing blood, or leg swelling. NHS guidance on pericarditis and pulmonary embolism describe these features.

Seek emergency care now if you have any chest pressure/heaviness, pain spreading to the arm, jaw, back, or neck, shortness of breath, fainting, sweating, nausea, rapid heartbeat, coughing blood, or new one-sided calf swelling. Do not drive yourself.

Even without those features, new unexplained retrosternal pain with breathing should be assessed urgently today, especially if it is persistent, worsening, follows recent travel/immobility/surgery, or you have fever or cough. A clinician may need to check your vital signs, ECG, and lungs.