Pulmonary embolism Flashcards
Define pulmonary embolism
A condition in which one or more emboli, usually arising from a thrombus formed in the veins, are lodged in and obstruct the pulmonary arterial system, causing severe respiratory dysfunction.
Define provoked PE
Associated with an antecedent (within 3 months) and transient risk factor, e.g. immobility, surgery, trauma, pregnancy or puerperium, and the use of the COCP or HRT.
Define unprovoked PE
Absence of a transient risk factor - e.g. active cancer, thrombophilia (risks can’t be removed)
Pulmonary embolism (PE) pathophysiology
Emboli(s), usually arising from a thrombus formed in the veins, lodges in and obstructs the pulmonary artery(ies).
- -> lung tissue is ventilated but not perfused, resulting in an intra-pulmonary dead space and impaired gas exchange.
- -> reduction in cross-sectional area of pulmonary arterial bed
- -> elevation of pulmonary arterial pressure and reduction in cardiac output
- -> alveolar collapse, which worsens hypoxaemia
- -> hyperventilation and respiratory alkalosis
What happens in a massive PE?
Large or multiple emboli can abruptly increase pulmonary arterial pressure to a level of afterload which cannot be matched by the right ventricle. Sudden death may occur, or the person may present with hypotension or syncope, which might progress to shock or death due to acute right ventricular failure.
What are the non-thrombotic sources of emboli? (6)
Tumours e.g. prostate and breast cancers Fat e.g. long-bone fractures Amniotic fluid Sepsis e.g. endocarditis Foreign bodies e.g. IVDU, broken medical equipment Air e.g. surgery
What is Virchow’s triad?
Hypercoagulability
Venous stasis
Vascular wall damage
Major risk factors for PE (7)
Deep vein thrombosis Previous VTE Active cancer Recent surgery Significant immobility e.g. bed rest, hospital admission Lower limb trauma or fracture Pregnancy and postpartum
Other risk factors for PE (9)
>60yo COCP or HRT Obesity Significant medical comorbidities e.g. heart disease Long distance travel Varicose veins Superficial venous thrombosis Known thrombophilias Other e.g. central vein catheter, nephrotic syndrome, chronic dialysis, myeloproliferative disorders, Behcet's
Complications of PE
Mortality, morbidity, and hospitalization
Chronic thromboembolic pulmonary hypertension (rare)
What is CTEPH?
Chronic thromboembolic pulmonary hypertension
Emboli replaced with fibrous tissue, leading to chronic obsutrction and increased pulmonary arterial pressure, which can lead to right heart failure
Symptoms of PE
May be asymptomatic
Sudden and severe pleuritic chest pain
Dyspnoea
Features of DVT (e.g. leg pain/swelling)
Retrosternal chest pain (due to right ventricular ischaemia)
Cough and haemoptysis
Dizziness and/or syncope (due to right ventricular failure)
Signs of PE
Tachycardia Tachypnoea Hypoxia Pyrexia Elevated JVP Gallop rhythm, a widely split second heart sound, tricuspid regurgitant murmur Pleural rub Hypotension and cardiogenic shock (rare signs indicating central PE and/or a severely reduced haemodynamic reserve).
Chest x-ray features in PE
Atelectasis, pleural effusion, or elevation of a hemidiaphragm
Wedge opacity
ECG features in PE
Sinus tachycardia
Non-specific ST-segment and T-wave abnormalities
Right axis deviation
Right bundle-branch block
T-wave inversion in leads V1–V3
P pulmonale (increased P wave amplitude)
S1Q3T3 (large S wave in lead 1, large Q wave in lead 3, and T-wave inversion in lead 3)
Respiratory differentials for PE
Pneumothorax
Pneumonia
Acute bronchitis
Acute exacerbation of asthma /COPD/chronic lung disease
Cardiac differentials for PE
Acute coronary syndrome Acute congestive heart failure Dissecting or rupturing aortic aneurysm Unstable angina Myocardial infarction Pericarditis
Other differentials for PE
Musculoskeletal chest pain
GORD
Panic disorder
Any cause of syncope e.g. vasovagal, postural hypotension, arrythmias, seizures, CVD
Differentials for pleuritic chest pain (5)
Pneumonia PE Pneumothorax Pleurisy Pericarditis
Diagnosing PE
History + exam
CXR or ECG to exclude other causes if necessary
ABGs
Well’s score - if >4, arrange immediate CTPA. If less than or equal to 4, arrange D-dimer test. If positive, arrange immediate CTPA.
If there is a delay in getting CTPA, give interim LMWH.
What is the PE Well’s score? (7)
Clinical features of deep vein thrombosis +3 points
Tachycardia +1.5 points
Immobilization >3 days or surgery in the previous 4 weeks +1.5 points
Previous DVT or PE +1.5 points
Haemoptysis +1 point
Cancer (receiving treatment, treated in the last 6 months, or palliative) +1 point
Alternative diagnosis is less likely than PE +3 points
What is the use of V-Q or perfusion scintigraphy in diagnosing PE?
May be done in certain circumstances e.g. half-dose perfusion scintigraphy in pregnancy, or if allergy to contrast, or renal impairment
Not very specific (40%)
What is the use of echo in diagnosing PE?
For people with hypotension (clinically ‘massive’ PE). The absence of right heart failure excludes PE.
?To exclude pericarditis
Pharmacological treatment for confirmed PE
Low molecular weight heparin
Fondaparinux
Unfractionated heparin
Oral anticoagulant treatment (warfarin, apixaban, or rivaroxaban)
LMWH followed by an oral anticoagulant (dabigatran or edoxaban)
USUALLY LMWH/FONDAPARINUX INITIALLY (for at least 5 days) AND THEN WARFARIN WITHIN 24 HOURS (for at least 3 months)
Mechanical treatments may be offered in some cases. What are the options?
1) Permanent or temporary IVC filters - trap thromboemboli en route to the pulmonary circulation
2) Thrombolytic therapy - peripheral vein or directly into pulmonary arteries, e.g. streptokinase (plasminogen activators)
3) Open pulmonary embolectomy (surgical removal of clots)
What follow up for those with unprovoked PE?
Offer investigations to assess for cancer - CXR, FBC, calcium, LFTs, urinalysis, CT scan +/- mammogram if >40yo
Offer antiphospholipid testing
Consider thrombophilia testing
Enoxaparin and tinzaparin - mechanism, place in therapy, side effects, monitoring
Mechanism = LMWH, activates anti-thrombin III and forms a complex that inhibits thrombin, factors Xa, IXa, XIa, XIIa
Indicated to treat VTE in pregnancy, and in patients with risk factors such as obesity, cancer, recurrent VTE, and in uncomplicated patients with low risk of recurrence.
It is also used for prophylaxis.
Used if PE in cancer.
Side effects - haemorrhage, heparin-induced thrombocytopenia, skin reactions, thrombocytopenia, thrombocytosis, alopecia, hyperkalaemia, osteoporosis, priapism
Monitoring - routine monitoring not recommended,
if so anti-Factor Xa
Fondaparinux - mechanism, place in therapy, side effects
Mechanism = synthetic pentasaccharide that inhibits activated factor X.
Used for prophylaxis and treatment.
Side effects - anaemia; haemorrhage; chest pain; coagulation disorder; dyspnoea; fever; hepatic function abnormal; nausea; oedema; platelet abnormalities; skin reactions; thrombocytopenia; vomiting; wound secretion
Unfractionated heparin - mechanism, place in therapy, side effects
Treatment of mild to moderate or severe pulmonary embolism
Also used for prophylaxis in medical and surgical patients, and also in pregnancy
Mechanism - activates anti-thrombin III
Side effects - haemorrhage, heparin-induced thrombocytopenia, skin reactions, thrombocytopenia, thrombocytosis, alopecia, hyperkalaemia, osteoporosis, priapism
Warfarin - mechanism, place in therapy, side effects, monitoring
Mechanism – inhibits reduction of vitamin K to its active form, which in turns acts as a cofactor in the carboxylation of clotting factor II, VII, IX, X and protein C
Used in prophylaxis and treatment
Side effects –
haemorrhage, alopecia, nausea, vomiting, abnormal LFTs, skin necrosis, skin reactions, pancreatitis, jaundice, blue toe syndrome
Monitoring - INR, target 2.5 or 3.5 if recurrent
Used for 3 months, or 6 months if unprovoked
Apixaban, rivaroxaban mechanism
Direct factor Xa inhibtior
Dabigatran mechanism
Direct thrombin inhibitor
Management of massive PE
ABCDE
Initiate unfractionated heparin
Get ICU input
Thrombolysis = first-line if haemodynamically unstable
