Pulmonary embolism is one of the important causes of acute chest pain . It can mimic acute coronary syndrome . In fact along with aortic dissection , it forms a differential diagnosis for STEMI especailly if the ECG is not typical.
The Chest pain of acute pulmonary embolism can originate in one of the following structures with different mechanism
- Lung parenchyma ( Necrotic pain ?)
- Pluritic pain in adjacent necrotic segment
- Main Pulmonary artery and it’s branches
- Right ventricular mechanical stretch
- Right ventricular ischemia
- Hypoxia induced LV ischemia with coexisting CAD.
- Multiple contribution from any of the above *
It should also be remembered , medicine never respects logic, as some times an episode of pulmonary embolism can occur without any chest pain
Localisation of chest pain
One can imagine , how difficult for the nervous system to zero in on the origin of this pain as the structures involved in acute pulmonary embolism are in different planes and in different depths within the chest cavity . Patients often complain vaguely the site of pain but what is universal is severe resting pain deep within the chest . If the ischemic lung segment transmit pain signals , the location and radiation depend on the bronchpulmonary segment involved.This again adds on to the complexity in the genesis of pain .It can be virtually any where in the back or front of chest.
But , the central and retrosternal chest pain are equally common as invariably the central pulmonary arteries go for a acute stretch which can be severely painful .In fact , current thinking is it could contribute maximum for the intensity of chest pain. Similarly, acute dilatation of RV result in mechanical pain. RV sub endocardial ischemia may also contribute .An intact bronchial circulation( From aorta) can limit the ischemic lung pain .
Analysing the chest pain of acute pulmonary embolism can be an interesting academic exercise . It could arise from multiple structures with different mechanisms. It may not be much significant with reference to management . But it has a diagnostic role. A pain which is severe , and atypically located should raise the suspicion of acute PE especially if the patient has associated dyspnea.