Clinical Characteristics
Pulmonary embolism (PE) presents a wide range of characteristics, from no symptoms to shock or sudden death.
The most common symptom is dyspnea followed by chest pain (classically but not always pleuritic) and cough. However, many patients, including those with significant PE, have mild symptoms or are asymptomatic.
●Initial tests – In patients with symptoms compatible with pulmonary embolism, tests including electrocardiography (ECG), chest X-ray, brain natriuretic peptide (BNP) levels, and troponin should be performed. However, these tests are neither sensitive nor specific for the diagnosis of PE and are very useful for confirming the presence of alternative diagnoses or providing prognostic information in the event of a PE diagnosis.
●Hemodynamically unstable patients
•With a high clinical suspicion of PE, who are hemodynamically unstable and successfully resuscitated, immediate anticoagulation and definitive diagnostic imaging are preferable.
•With a low or moderate suspicion of PE who are successfully resuscitated, the same diagnostic and empirical anticoagulation approach should be used as for hemodynamically stable patients.
•For patients who remain unstable despite resuscitation, bedside echocardiography and lower limb compression ultrasound (ultrasound) with Doppler of the leg veins can be used to obtain a rapid or presumptive diagnosis of PE (visualization of a thrombus or new right heart strain) to justify the administration of potentially life-saving therapies, including thrombolytic agents.
●Hemodynamically stable patients – For patients suspected of PE who are hemodynamically stable, we suggest an approach that selectively integrates clinical assessment, three-level pre-test probability tests (e.g., clinical gestalt or Wells criteria, PE exclusion criteria (PERC), D-dimer and imaging Pulmonary CT angiography (CTPA), also called chest angiography with contrast agent, is the preferred imaging examination.
•In patients with a low clinical probability of PE (e.g., <15 percent, Wells score <2), PERC should be applied. Patients who meet all eight criteria do not need further testing. For patients who do not meet PERC criteria or for whom PERC cannot be applied, further testing with a sensitive D-dimer measurement is indicated; no imaging is required when the D-dimer level is normal (<500 ng/mL [fibrinogen equivalent units]), while imaging is indicated in those with a positive D-dimer.
A positive D-dimer can be defined as ≥ 500 ng/mL (fibrinogen equivalent units) or a value above the age-adjusted or pre-test probability-adjusted threshold (e.g., YEARS). Adjusted D-dimer levels based on certain criteria have been proposed and may be considered an alternative in patients with low (or low-intermediate probability for PE). They should not be used in those with a high or intermediate-high probability of PE.
•In patients with an intermediate clinical probability of PE (e.g., Wells score 2 to 6), we prefer sensitive D-dimer testing to determine whether diagnostic imaging is indicated or not. Patients with a negative D-dimer do not need imaging while those with a positive D-dimer should undergo chest imaging. However, some experts proceed directly to diagnostic imaging in certain patients (e.g., those with limited cardiopulmonary reserve or those in the upper range of the intermediate range like a Wells score of 4 to 6).
•In patients with a high clinical probability of PE (e.g., Wells score > 6), we prefer diagnostic imaging with CTPA. A positive result confirms the diagnosis of PE while a negative result excludes it in almost all cases.
CTPA acquires thin-slice volumetric images (≤ 2.5 mm) of the chest after a precisely timed intravenous contrast bolus administration for maximal enhancement of the pulmonary arteries. A multi-detector row CT scanner (≥ 16 detector rows) is required to achieve sufficient diagnostic performance. A chest CT scan with contrast not performed as a CTPA but for other indications is not an adequate examination to exclude suspected pulmonary embolism.
●Alternative imaging approaches
• Ventilation and perfusion scan (V/Q) – For patients suspected of pulmonary embolism for whom CTPA is contraindicated, unavailable, or inconclusive, the V/Q scan is the alternative imaging examination. V/Q scan results, reported as having a high, intermediate, or low probability of PE, or normal, should be interpreted in conjunction with clinical suspicion. A high-probability V/Q scan and high clinical probability are sufficient to confirm PE. A normal scan or a low-probability scan in a context of low clinical probability of PE can also be used to exclude PE. All other combinations of V/Q results and clinical probability are not diagnostic.
•Other tests – For patients for whom CT and V/Q CT are contraindicated, unavailable, or inconclusive, we prefer non-invasive tests with lower limb compression ultrasound with Doppler (although they do not allow diagnosing PE).
●Diagnosis – A diagnosis of PE is made radiographically based on a CTPA, magnetic resonance pulmonary angiography (MRPA), or catheter pulmonary angiography by demonstrating a filling defect in any branch of the pulmonary artery. With V/Q scan, a high-probability scan with high clinical probability confirms PE.
●Differential diagnosis – The differential diagnosis of PE includes many other entities that present similarly with dyspnea, chest pain, hypoxemia, leg pain and swelling, tachycardia, syncope, and shock. Other competing diagnoses, including heart failure, myocardial ischemia, pneumothorax, pneumonia, and pericarditis, can be distinguished by electrocardiographic, echocardiographic, laboratory, and chest radiographic tests. However, PE can coexist with these pathologies and, therefore, the presence of another diagnosis does not completely exclude the diagnosis of PE.
Source: UpToDate