Non-imaging Diagnosis of Pulmonary Embolism

Pulmonary Embolism (PE) is frequent in clinical practice and can lead to significant sequelae: prompt diagnosis is imperative to enable early treatment and improve outcomes. However, making the diagnosis is not always simple and PE can be quite elusive. The clinical symptoms and signs of PE are not specific and the clinical presentation varies considerably, depending on the severity of the obstruction as well as the background status of the patient. PE can be completely asymptomatic, cause dyspnea, pleuritic chest pain and syncope or present as cardiogenic shock and sudden death. The key to the diagnosis is a high index of suspicion. When PE is suspected, patients should be classified according to the probability of a diagnosis of PE as low, intermediate or high. This estimation is based on typical symptoms, signs and predisposing factors for venous thromboembolism. This probability assessment is imperative as it will dictate further steps to make the most efficient pathway to the diagnosis or rule-out of PE. It is possible to use clinical judgement or one of the standardized scores to calculate the probability risk of PE. We recommend using the simplified Geneva or simplified Wells scores for probability assessment that are simple and predictive. Patients with low or intermediate risk should undergo D-dimer assay testing that has a very high negative predictive value; a negative assay rules out PE with a high sensitivity. A positive result requires further imaging evaluation. Patients with a high pretest probability should undergo directly an imaging study, primarily by CTPA, to make the diagnosis of PE. The ECG, although non-specific, may increase the index of suspicion for PE as well as provide prognostic information. Cardiac biomarkers are nonspecific but provide important prognostic information. Troponin, a marker of right ventricular myocardial injury identifies patients at high risk for adverse outcome. Measuring BNP levels, although not routinely recommended, is also useful in the risk stratification and prognosis of patients with a large PE.