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Diagnosis of Pulmonary Embolism With Magnetic Resonance Angiography FREE

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The summary below is from the full report titled “Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism. A Multicenter Prospective Study (PIOPED III).” It is in the 6 April 2010 issue of Annals of Internal Medicine (volume 152, pages 434-443). The authors are P.D. Stein, T.L. Chenevert, S.E. Fowler, L.R. Goodman, A. Gottschalk, C.A. Hales, R.D. Hull, K.A. Jablonski, K.V. Leeper Jr., D.P. Naidich, D.J. Sak, H.D. Sostman, V.F. Tapson, J.G. Weg, and P.K. Woodard, for the PIOPED III (Prospective Investigation of Pulmonary Embolism Diagnosis III) Investigators.

Ann Intern Med. 2010;152(7):I-44. doi:10.7326/0003-4819-152-7-201004060-00004
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What is the problem and what is known about it so far?

Pulmonary embolism (PE) is a blockage of an artery in the lung. It usually occurs when a blood clot from a deep vein in the legs becomes dislodged and travels through the heart to the arteries of the lungs. Pulmonary embolism can be fatal if it is not treated quickly, and it can be difficult to diagnose. Doctors typically use history and physical examination, blood tests (d-dimer assays and arterial blood oxygen levels), ultrasonography or x-rays with dye injections of the leg veins (venograms), and lung radioisotope injections or computed tomography scans (CAT scans) of the arteries in the lungs to diagnose PE. They also may insert dye into the blood vessels of the lungs, by using a tube inserted in a leg vein and threaded through the heart, to see blockages in the arteries in the lungs (pulmonary angiography).

A more recent proposed test to diagnose PE is gadolinium-enhanced magnetic resonance angiography (MRA). This test uses a standard magnetic resonance imaging (MRI) unit. It involves injecting a chemical (gadolinium) that enhances MRA images of blood vessels.

Why did the researchers do this particular study?

To see whether gadolinium-enhanced MRA is a feasible, accurate test for diagnosing PE.

Who was studied?

371 adults from 7 hospital and emergency department sites.

How was the study done?

The researchers recruited patients with suspected PE. They excluded those who declined or could not give consent; were critically ill or could not lie still; were pregnant or nursing; or had kidney problems, a recent heart attack, claustrophobia, or an implanted or external device that precluded MRA. Participating patients had PE diagnosed or excluded with standard tests. Those with diagnosed PE and a sample of those with excluded PE then had gadolinium-enhanced MRA. Two doctors, who had no knowledge of the results of other tests that were used to diagnose PE, interpreted the MRA results. The researchers then examined data to see whether MRA correctly identified the patients who did and did not have PE according to the standard tests.

What did the researchers find?

In 25% of the patients who had MRA, the test was technically inadequate because of poor-quality images. Numbers of technically inadequate tests varied across the 7 hospitals. The procedure identified 57% of the 104 patients who had PE according to standard tests. In patients with technically adequate MRA, 78% with PE were identified, and 99% of those in whom PE was excluded were correctly identified.

What were the limitations of the study?

Many patients with suspected PE declined to participate in the study or were excluded because they were not eligible.

What are the implications of the study?

Gadolinium-enhanced MRA to diagnose PE is not always feasible and is often technically inadequate. Patients should have the test done only at centers that routinely perform it well and only if standard tests cannot be performed.





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