Clinical Review

Fortnightly review : the diagnosis of pulmonary embolism

BMJ 1997; 314 doi: https://doi.org/10.1136/bmj.314.7078.425 (Published 08 February 1997) Cite this as: BMJ 1997;314:425
  1. Tony Fennerty, consultant physiciana
  1. a Chest Clinic Southern General Hospital Glasgow G51 4TF
  • Accepted 6 December 1996

Introduction

Pulmonary emboli are responsible for 10% of all deaths in hospital (medical and surgical), and contribute to a further 10%.1 Death occurs in a heterogeneous group of patients ranging from those who are terminally ill to those who are convalescent. It is usually a sudden event but not always unheralded and often predictable. Thromboprophylaxis and a high level of suspicion are the only means by which any impression is likely to be made on the current death rate, which has not changed in the past 30 years.1 Once treatment is started death from pulmonary embolism is rare, the problem is diagnosing it. The only confirmatory test available to most clinicians is ventilation perfusion lung scanning, but it is truly diagnostic in only about 30% of cases. The remaining 70% of scans–that is, low and intermediate probability scans, sometimes referred to as non-diagnostic scans–may represent a probability for an underlying embolus of between 4% and 66%, depending on the clinical circumstances and the scan abnormality.2 Most clinical guidelines refer patients with a non-diagnostic scan for pulmonary angiography, the gold standard diagnostic test for pulmonary embolus, ignoring the fact that angiography is not available to many clinicians in the United Kingdom. Clinicians thus have to make clinical decisions on the basis of somewhat broad diagnostic probabilities.

How do they cope? We do not know for sure, but in most cases treatment is probably withheld.3 When an uncertain diagnosis is balanced against the perceived risks and inconveniences of anticoagulant treatment concerns about anticoagulants are likely to win over any concerns over dying of pulmonary embolism. But how fatal is pulmonary embolism?

Remarkably little is known about the natural course of the condition, but a death rate of 30% for an untreated pulmonary embolus is often quoted and accounts for …

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