Pulmonary Embolism Flashcards
What is pulmonary embolism?
Pulmonary embolism (PE) is a condition where a blood clot (thrombus) forms in the pulmonary arteries. This is usually the result of a deep vein thrombosis (DVT) that developed in the legs and travelled (embolised) through the venous system and the right side of the heart to the pulmonary arteries in the lungs. Once they are in the pulmonary arteries they block the blood flow to the lung tissue and create strain on the right side of the heart. DVTs and PEs are collectively known as venous thromboembolism (VTE).
What are the risk factors?
Immobility
Recent surgery
Long haul flights
Pregnancy
Hormone therapy with oestrogen
Malignancy
Polycythaemia
Systemic lupus erythematosus
Thrombophilia
What is VTE prophylaxis?
prophylaxis with a low molecular weight heparin such as enoxaparin unless contraindicated. Contraindications include active bleeding or existing anticoagulation with warfarin or a NOAC. Anti-embolic compression stockings are also used unless contraindicated. The main contraindication for compression stockings is significant peripheral arterial disease.
Presentation
Shortness of breath
Cough with or without blood (haemoptysis)
Pleuritic chest pain
Hypoxia
Tachycardia
Raised respiratory rate
Low grade fever
Haemodynamic instability causing hypotension
What is Wells Score?
The Wells score predicts the risk of a patient presenting with symptoms actually having a DVT or pulmonary embolism. It takes in to account risk factors such as recent surgery and clinical findings such as tachycardia (heart rate >100) and haemoptysis.
How do we diagnose?
History
Examination
Chest xray
Perform a Wells score and proceed based on the outcome:
Likely: perform a CT pulmonary angiogram
Unlikely: perform a d-dimer and if positive perform a CTPA
How does CTPA and VQ scan work?
CT pulmonary angiogram (CTPA) involves a chest CT scan with an intravenous contrast that highlights the pulmonary arteries to demonstrate any blood clots. This is usually the first choice for investigating a pulmonary embolism as it tends to be more readily available, provides a more definitive assessment and gives information about alternative diagnoses such as pneumonia or malignancy.
Ventilation-perfusion (VQ) scan involves using radioactive isotopes and a gamma camera to compare the ventilation with the perfusion of the lungs. They are used in patients with renal impairment, contrast allergy or at risk from radiation where a CTPA is unsuitable. First, the isotopes are inhaled to fill the lungs and a picture is taken to demonstrate ventilation. Next a contrast containing isotopes is injected and a picture is taken to demonstrate perfusion. The two pictures are then compared. With a pulmonary embolism there will be a deficit in perfusion as the thrombus blocks blood flow to the lung tissue. This area of lung tissue will be ventilated but not perfused.
Management
-The initial recommended treatment is apixaban or rivaroxaban. Low molecular weight heparin (LMWH) is an alternative where these are not suitable, or in antiphospholipid syndrome. It should be started immediately before confirming the diagnosis in patients where DVT or PE is suspected and there is a delay in getting the scan. Examples are enoxaparin and dalteparin.
The options for long term anticoagulation in VTE are warfarin, a DOAC (The main three options are apixaban, dabigatran and rivaroxaban.) or LMWH. for 3 months first
Where there is a massive PE with haemodynamic compromise - thrombolysis. Thrombolysis involves injecting a fibrinolytic medication (they break down fibrin) that rapidly dissolves clots. There is a significant risk of bleeding which can make it dangerous. It is only used in patients with a massive PE . Some examples of thrombolytic agents are streptokinase, alteplase and tenecteplase.
There are two ways thrombolysis can be performed:
Intravenously using a peripheral cannula.
Directly into the pulmonary arteries using a central catheter. This is called catheter-directed thrombolysis.
