Pulmonary Embolism

Pulmonary emboli occur as the result of a thrombus (generally formed in the systemic veins) dislodging and embolising in the pulmonary arterial system.

Thrombi (or “clots”) form are caused due to a combination of three factors. These are often referred to as Virchow’s triad and encompass stasis of blood flow, hypercoagulability of the blood and endothelial damage of the vessel walls. Emboli can also occur from tumour, fat (from long bone fractures) amniotic fluid and foreign material injected during i.v. drug use.

The clinical features of pulmonary embolism are often rather vague, but unexplained dyspnoea is the most common (and often the sole) symptom. Pleuritic chest pain and haemoptysis (coughing blood) are present only when infarction has occurred. Many pulmonary emboli occur silently, but there are three typical clinical presentations.

Small/medium pulmonary embolism – an embolus has impacted in a terminal pulmonary vessel. Symptoms are pleuritic chest pain and dyspnoea. Haemoptyis occurs in 30% of cases, often 3+ days after the event. On examination the patient may be tachypnoeic with a localised pleural rub and an exudative pleural effusion can develop. The patient may have a fever, and cardiovascular examination is normal

Massive pulmonary embolism – much rarer, it involves sudden collapse because of an acute obstruction of the right ventricular outflow tract. The patient has severe central chest pain (cardiac ischaemia due to lack of coronary blood flow) and becomes shocked, pale and sweaty. Syncope may result if the cardiac output is transiently but dramatically reduced, and death may occur. On examination, the patient is tachypnoeic, has a tachycardia with hypotension and peripheral shutdown.

Multiple recurrent pulmonary emboli
This leads to increased breathlessness often over weeks or months. It is accompanied by weakness, syncope on exertion and occasionally angina. The physical signs are due to pulmonary hypertension that has developed from multiple occlusions of the pulmonary vasculature.

Diagnosis
The symptoms and signs of small and medium-sized pulmonary emboli are often subtle and non-specific, so the diagnosis is often delayed or even completely missed. Pulmonary embolism should be considered if patients present with symptoms of unexplained cough, chest pain, haemoptysis, new-onset atrial fibrillation (or other tachycardia), or signs of pulmonary hypertension

Investigations – include chest x-ray, plasma D-dimer, ECG, full bloods and radionuclide ventilation/perfusion scanning (V/Q scan)

Treatment
Oxygen, bed rest, heparin and analgesia

References - Kumar and Clarke, emedicine, wikipedia
By Steph