Essence of this Article
Pulmonary embolism (PE) occurs when a part of a thrombus, usually dislodged from a deep vein thrombosis (DVT), passes into the pulmonary circulation, occluding the pulmonary arteries. PE is a potentially life-threatening condition and is the most common reason for preventable hospital death. Rapid diagnosis is crucial however the diagnosis of PE may be missed because of its non-specific clinical symptoms. Long-term complications of PE include chronic thromboembolic pulmonary hypertension (CTEPH). The Wells score is one scoring system that is commonly used to predict clinical probability of PE. Ventilation-perfusion scanning had been the first-line approach in patients with suspected PE for decades, although other diagnostic methods are available.
PE is a potential cardiovascular emergency and occurs when a part of a thrombus, usually dislodged from a DVT (and then called an embolus), passes into the pulmonary circulation, occluding the pulmonary arteries. Nearly four-fifths of patients with PE have evidence of DVT,144 and approximately half of those with proven proximal DVT have an associated PE and, like DVT, PE is often asymptomatic.145 However, approximately 20–30% of cases are unprovoked (idiopathic).146
Epidemiological data indicate that, of the more than 1.1 million cases of VTE occur in the EU each year, approximately one-third are PE cases.124 PE is the most common reason for preventable hospital death.119 Long-term complications of PE include chronic thromboembolic pulmonary hypertension (CTEPH), which can have serious consequences.147, 148
Diagnosis of PE
Signs and symptoms
PE is a potentially life-threatening condition and in severe cases, the occurrence of circulatory collapse and cardiac arrest may result in sudden death. Early fatality occurs in up to 15% of patients,146 and thus rapid diagnosis is crucial. However, the diagnosis of PE may be missed because of its non-specific clinical symptoms.146
- Chest pain
- Respiratory crackles (crepitations)
These symptoms are not specifically diagnostic of PE.144 For this reason, the diagnostic process, and decisions regarding the need for imaging studies specifically designed to detect PE, should begin with a careful clinical examination and a determination of the likelihood that the patient has suffered a PE.
The clinical severity of PE varies depending on the patient’s baseline cardiopulmonary reserve, the size of the embolus, and the degree to which the embolus occludes the pulmonary circulation. A massive PE can cause cardiogenic shock, while small emboli may be asymptomatic.
A clinician should maintain a high index of suspicion for this condition, because prompt treatment of PE can dramatically reduce the morbidity and mortality of the disease.
Clinical probability scores
Scoring systems used in clinical practice include several key risk factors and markers for PE based on patient history and presentation. The Wells score is one scoring system that is commonly used method to predict clinical probability of PE.134 This prediction rule has been revised several times since its development to make it simpler and more accurate.149
Wells score for prediction of PE.149
A total score >6 indicates a high probability of a PE, a score of 2−6 moderate probability and a score <2 low probability.149
|Clinically suspected DVT||3|
|Alternative diagnosis less likely than PE||3|
|Rapid heart rate||1.5|
|Immobilization within past 4 weeks||1.5|
|History of DVT||1.5|
|DVT, deep vein thrombosis; PE, pulmonary embolism.|
Ventilation-perfusion scanning had been the first-line approach in patients with suspected PE for decades. A ventilation-perfusion scan indicating a high probability of PE provides sufficient evidence for the initiation of treatment, although it should be noted that a scan indicating a low probability of PE does not rule out the condition.150 Spiral CT has a high sensitivity and specificity for detecting large pulmonary emboli but is generally unable to detect small ones. One method that is used for diagnosis is CT pulmonary angiography. This is rarely a first-line diagnostic test, because it is more invasive than either ventilation-perfusion scans or spiral CT.126
Combined diagnostic methods
A number of diagnostic methods can be used to assess patients with suspected PE, including the use of a simple clinical prediction rule, D-dimer testing and CT. The efficacy of these methods as a combined approach was evaluated in a prospective cohort study involving over 3300 patients, and it was shown that this method could be applied in 98.5% of eligible patients, while effectively guiding the clinical management decision in 97.9% of patients.151 The European Society of Cardiology (ESC) has issued algorithms for the diagnosis of PE depending on whether the risk of death based on clinical symptoms is judged to be high or not.146 High-risk PE in this context is usually suspected if shock and/or hypotension are present.
ESC algorithm for the confirmatory diagnosis of potentially fatal PE. Adapted from Torbicki et al.146 ai.e. with shock and/or hypotension ; bnot available if the patient’s condition allows bedside diagnostic tests only; ctransoesophageal ECG may detect pulmonary arterial thrombi in a significant proportion of patients with RV overload and PE that is ultimately confirmed by spiral CT. Confirmation of DVT with bedside compression ultrasonography could also assist decision-making. CT, computed tomography; ECG, electrocardiography; PE, pulmonary embolism; RV, right ventricular.
ESC guidelines for the diagnosis of PE where the clinical symptoms are not suggestive of a high risk of death. Adapted from Torbicki et al.146 ai.e. not with shock and/or hypotension; be.g. Wells score. CT, computed tomography; PE, pulmonary embolism.
Risk factors for recurrence
As with DVT, the risk of recurrent PE appears to be higher in patients with an initial unprovoked PE and/or persistent risk factors than in those with transient risk factors.152
Persistent risk factors include:152
- Active cancer
- Elevated levels of antiphospholipid antibodies
- Elevated D-dimer concentration after discontinuation of therapy
Several studies have indicated that patients with an initial PE are at high risk of recurrent PE,153, 154 and one meta-analysis suggested that the risk for recurrent PE is 3.1-fold greater in patients who have had an initial symptomatic PE than in those with initial proximal DVT.155