A (thromboembolism) occurs when a
Blood Clot , generally a
Venous thrombus, becomes dislodged from its site of formation and
Embolizes to the
Arterial blood supply of one of the
Lung s. Symptoms may include
Difficulty Breathing ,
Pain during breathing, and more rarely circulatory instability and
Death . Treatment is with
Anticoagulant medication, such as
Warfarin .
Signs of PE are sudden-onset
Dyspnea (shortness of breath, 73%),
Tachypnea (rapid breathing, 70%),
Chest Pain of "pleuritic" nature (worsened by breathing, 66%),
Cough (37%),
Hemoptysis (coughing up blood, 13%), and in severe cases,
Cyanosis ,
Tachycardia (rapid heart rate),
Hypotension ,
Shock ,
Loss Of Consciousness , and death. Although most cases have no clinical evidence of
Deep Venous Thrombosis (DVT) in the
Leg s, findings that indicate DVT may aid in the diagnosis.
The most common sources of embolism are proximal leg
Deep Venous Thrombosis (DVTs) or pelvic vein thromboses. Any risk factor for DVT also increases the risk that the venous clot will dislodge and migrate to the lung circulation, which happens in up to 15% of all DVTs.
Risk factors for DVT and PE (together "venous thromboembolism" or VTE) can be divided into ''
Genetic '', ''acquired'' and ''circumstantial'' causes. In many occasions, more than one risk factor is present:
The
Gold Standard for diagnosing pulmonary embolism (PE) is
Pulmonary Angiography . In most cases, however, when PE is suspected on the basis of shortness of breath and chest pain, the following studies may confirm the presence of an embolus. Pulmonary angiography is used less often because of wider acceptance of CT scans, which are non-invasive.
- , effectively a pulmonary angiogram imaged by CT, is increasingly used as the mainstay in diagnosis. Advantages are clinical equivalence, better access for patients and the possibility of picking up other lung disorders from the Differential Diagnosis in case there is no pulmonary embolism.
- (or ''V/Q scan''), which shows that some areas of the lung are being ventilated but not perfused with blood (due to obstruction by a clot). It is a type of Scintigraphy . This study is used less often because of CT technology, however, it may be useful in patients who have an allergy to Iodinated Contrast
In low/moderate suspicion of PE, a normal
D-dimer level (shown in a
Blood Test ) is enough to exclude the possibility of PE.Bounameaux H, de Moerloose P, Perrier A, Reber G. Plasma measurement of D-dimer as diagnostic aid in suspected venous thromboembolism: an overview. ''Thromb Haemost'' 1994;71:1-6. PMID 8165626.
An
Electrocardiogram may show signs of right heart strain or acute ''
Cor Pulmonale '' in cases of large PEs - the classic signs are a large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III ("S1Q3T3").McGinn S, White PD. Acute cor pulmonale resulting from pulmonary embolism. ''J Am Med Assoc'' 1935;104:1473–1480. This is occasionally (up to 20%) present, but may also occur in other acute lung conditions and has therefore limited diagnostic value; The most commonly seen sign in the ECG is sinus tachycardia.
In massive PE, dysfunction of the right side of the heart can be seen on
Echocardiography (EKG), an indication that the
Pulmonary Artery is severely obstructed and the heart is unable to match the pressure. In the
United States , many physicians see this as an adequate indication for
Thrombolysis (see below).
The presence of
Deep Venous Thrombosis is in itself enough to warrant anticoagulation, without requiring the V/Q or spiral CT scans, and leg
Ultrasound can be used as a surrogate. This may be valid approach in pregnancy, in which the other modalities would increase the risk of birth defects in the unborn child. However, a negative scan does not rule out PE, and low-radiation dose scanning may be required if the mother is deemed at high risk of having pulmonary embolism.
When a PE is being suspected, a number of
Blood Test s are also done, in order to exclude important secondary causes of PE. This includes a
Full Blood Count ,
Clotting Status (
PT ,
APTT , TT), and some screening tests (
Erythrocyte Sedimentation Rate ,
Renal Function ,
Liver Enzyme s,
Electrolyte s). If one of these is abnormal, further investigations might be warranted.
Acutely, supportive treatments, such as
Oxygen or
Analgesia , are often required.
Massive PE causing hemodynamic instability (marked decreased
Oxygen Saturation ,
Tachycardia and/or
Hypotension ) is an indication for
Thrombolysis , the enzymatic destruction of the clot with medication. Some advocate its use also if right ventricular dysfunction can be demonstrated on
Echocardiography .Goldhaber SZ. Pulmonary embolism. ''
Lancet '' 2004;363:1295-305. PMID 15094276.
In most cases,
Anticoagulant therapy is the mainstay of treatment.
Heparin ,
Low Molecular Weight Heparin s, or
Fondaparinux is administered initially, while
Warfarin therapy is commenced (this may take several days, usually while the patient is in hospital). Warfarin therapy is usually continued for 3-6 months, or "lifelong" if there have been previous DVTs or PEs, or none of the usual risk factors is present. Warfarin therapy often requires frequent dose adjustment and monitoring of the
INR . In PE, INRs between 2.0 and 3.0 are generally considered ideal. If another episode of PE occurs under warfarin treatment, the INR window may be increased to e.g. 2.5-3.5 (unless there are contraindications) or anticoagulation may be changed to a different anticoagulant e.g.
Low Molecular Weight Heparin . In patients with an underlying malignancy, therapy with a course of
Low Molecular Weight Heparin may be favored over warfarin based on the results of the CLOT trial.
1 If anticoagulant therapy is
Contraindicated and/or ineffective an
Inferior Vena Cava Filter may be implanted.
Surgical management of acute pulmonary embolism (
Pulmonary Thrombectomy ) is uncommon and has largely been abandoned because of poor long-term outcomes. However, recently, it has gone through a resurgence with the revision of the surgical technique and is thought to benefit selected patients.Augustinos P, Ouriel K. Invasive approaches to treatment of venous thromboembolism. ''Circulation'' 2004 Aug 31;110(9 Suppl 1):I27-34. PMID 15339878.
Chronic pulmonary embolism leading to
Pulmonary Hypertension (known as ''chronic thromboembolic hypertension'') is treated with a surgical procedure known as a
Pulmonary Thromboendarterectomy .
Before anticoagulation became the accepted treatment, mortality from PE was about 26%.Barritt DW, Jorden SC. Anticoagulant drugs in the treatment of pulmonary embolism: a controlled trial. ''
Lancet '' 1960;1:1309-1312. PMID 13797091.
Prognosis depends on the amount of lung that is affected and on the co-existence of other debilitating conditions. Chronic embolisation to the lung can lead to
Pulmonary Hypertension .
After a first PE, the search for secondary causes is usually brief. Only when a second PE occurs, and especially when this happens while still under
Anticoagulant therapy, a further search for underlying conditions is undertaken. This will include testing (see above for full list) for Factor V Leiden mutation, antiphospholipid antibodies, protein C and S and antithrombin levels, and later prothrombin mutation, MTHFR mutation, Factor VIII concentration and rarer inherited
Coagulation abnormalities.
After a trial published in
1960 , anticoagulation became the most important therapeutic intervention in pulmonary embolism. Barritt and Jordan performed their study in the
Bristol Royal Infirmary in 1957. This study rapidly set the pace, considering that no other study of anticoagulation in confirmed PE ever had a placebo group (as this would have been unethical). Looking back, the reported mortality rate of 26% may have been an overstatement, given the fact that with the technology of the day, only severe PEs were detected.
A notable victim of pulmonary embolism was
William II , the last
Kaiser of
Germany .
