Comparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study

doi:10.1016/S0140-6736(02)08596-3

The Lancet

Volume 359, Issue 9318, 11 May 2002, Pages 1643-1647

https://doi.org/10.1016/S0140-6736(02)08596-3 Get rights and content

Summary

Background

Diagnostic strategies for pulmonary embolism are complex and consist of non-invasive diagnostic tests done to avoid conventional pulmonary angiography as much as possible. We aimed to assess the diagnostic accuracy of magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, using conventional pulmonary angiography as a reference method.

Methods

In a prospective study, we enrolled 141 patients with suspected pulmonary embolism and an abnormal perfusion scan. Patients underwent MRA before conventional pulmonary angiography. Two reviewers, masked with respect to the results of conventional pulmonary angiography, assessed MRA images independently. Statistical analyses used X² and 95% CI.

Findings

MRA was contraindicated in 13 patients (9%), and images were not interpretable in eight (6%). MRA was done in two patients in whom conventional pulmonary angiography was contraindicated. Thus, MRA and conventional pulmonary angiography results were available in 118 patients (84%). Prevalence of pulmonary embolism was 30%. Images were read independently in 115 patients, and agreement obtained in 105 (91%), K=0–75. MRA identified 27 of 35 patients with proven pulmonary embolism (sensitivity 77%, 95% CI 61–90). Sensitivity of MRA for isolated subsegmental, segmental, and central or lobar pulmonary embolism was 40%, 84%, and 100%, respectively (p<0·01 for isolated subsegmental vs segmental or larger pulmonary embolism). However, subgroups contained small numbers. MRA identified pulmonary embolism in two patients with normal angiogram (98%, 92–100).

Interpretation

MRA is sensitive and specific for segmental or larger pulmonary embolism. Results are similar to those obtained with helical computed tomography, but MRA has safer contrast agents and does not involve ionising radiation. MRA could become part of the diagnostic strategy for pulmonary embolism.

Introduction

Pulmonary embolism has an incidence of three suspected cases per 1000 inhabitants in the western world per year1, 2, 3 30–40% of these patients need anticoagulant drugs and have to be distinguished from those in whom anticoagulation can be safely withheld to avoid unnecessary risks3, 4, 5. The reference method, conventional pulmonary angiography, is invasive and carries an, albeit small, risk of complications6, 7. Hence, diagnostic strategies are often complex, consisting of non-invasive diagnostic tests, such as plasma D-dimer measurement, lung scintigraphy, and ultrasonography of the leg veins, to try to avoid conventional pulmonary angiography in as many patients as possible8, 9, 10.

Helical computed tomography (CT) has shown great promise for the diagnosis of pulmonary embolism11, 12 Improved techniques, decreased slice thickness, improved reconstruction, and faster CT scanners will enhance the diagnostic power of CT. However, use of CT for the safe exclusion of pulmonary embolism is currently restricted by its insensitivity to small, subsegmental emboli13, 14.

Magnetic resonance angiography (MRA) is another possible approach for diagnosis of suspected pulmonary embolism¹⁵. This diagnostic technique has safer contrast agents than CT and does not involve ionising radiation. MRA is rapidly improving, and with use of contrast-enhanced breath-hold techniques a detailed MRA of most body areas can be done. Furthermore, magnetic resonance imaging can be used to assess soft tissues, lung perfusion, and pulmonary angiography in a single investigation. Development of new and faster scanning sequences has enabled MRA to be done in shorter time spans than previously, allowing people who have difficulty in holding their breath for long periods to undergo MRA of the pulmonary vasculature. Finally, improved methods are being introduced that allow almost simultaneous imaging of ventilation and perfusion of the lung. Thus, magnetic resonance imaging is increasingly applied for diagnosis of a rising number of chest disorders.

We aimed to assess the diagnostic accuracy of MRA for diagnosis of pulmonary embolism, using conventional pulmonary angiography as the reference method, in non-selected patients with suspected pulmonary embolism.

Section snippets

Patients

We recruited consecutive patients from ongoing trials of diagnostic strategy in pulmonary embolism¹⁰ and the value of rapid plasma D-Dimer test in diagnosis of the disease.¹⁶ 141 patients with clinically suspected pulmonary embolism and an abnormal perfusion lung scintigram were referred for conventional pulmonary angiography. In these patients, MRA was done before conventional pulmonary angiography. All patients were managed on the basis of the conventional pulmonary angiography results. All

Results

The initial cohort was 141 patients, 61 men and 80 women, with a median age of 53 years (range 16–87). In 13 patients (9%), MRA could not be done for medical reasons, such as extreme dyspnoea, metal in orbits, or claustrophobia. In eight patients (6%), MRA was not interpretable because of insufficient contrast enhancement (four patients) or technical failure (four). In these 21 patients, DSA showed pulmonary emboli in three, and was normal in the remaining 18. Finally, MRA was done in two

Discussion

Our results show that the findings of MRA are similar to helical CT: there is good performance in larger (segmental or greater) emboli, whereas the diagnosis of (isolated) subsegmental pulmonary embolism is more difficult11, 12, 13, 19, 20. Few data exist that show the value and feasibility of MRA in patients with suspected pulmonary embolism¹⁵. These data are mainly based on selected patients with previously documented pulmonary embolism. MRA has many more advantages than helical CT. First, it

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ArticlesComparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study

Summary

Background

Methods

Findings

Interpretation

Introduction

Section snippets

Patients

Results

Discussion

Chest

Lancet

Am Heart J

A population-based perspective of the hospital incidence and case-fatality rates of deep vein thrombosis and pulmonary embolism: the Worcester DVT study

Arch Intern Med

Diagnosis, treatment and prevention of pulmonary embolism: report of the WHO/ISFC Task Force

JAMA

The diagnosis of venous thromboembolism: an overview

Bleeding complications in oral anticoagulant therapy: an analysis of risk factors

Arch Intern Med

Pulmonary angiography performed with iopamidol: complications in 1434 patients

Radiology

Feasibility, safety and clinical utility of angiography in patients with suspected pulmonary embolism and non-diagnostic lung scan findings

Eur Radiol

Management of venous thromboembolism

N Engl J Med

Active implementation of a consensus strategy improves diagnosis and management in suspected pulmonary embolism

Q J Med

Diagnosis of pulmonary embolism with spiral CT: comparison with pulmonary angiography and scintigraphy

Radiology

Role of spiral volumetric computed tomographic scanning in the assessment of patients with clinical suspicion of pulmonary embolism and an abnormal ventilation/perfusion lung scan

Thorax

Detection of pulmonary embolism in patients with unresolved clinical and scintigraphic diagnosis: helical CT versus angiography

AJR

Articles
Comparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study