COMPARISON
OF CONTRAST-ENHANCED MAGNETIC RESONANCE ANGIOGRAPHY AND CONVENTIONAL PULMONARY
ANGIOGRAPHY FOR THE DIAGNOSIS OF PULMONARY EMBOLISM: A PROSPECTIVE STUDY.
Oudkerk
M, et al. Lancet 2002 May 11;359(9318):1643-7
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 chi(2) 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%), kappa=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.
CONCLUSION:
This study basically demonstrates that MRA is not better then helical CT.