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08-01-2012 | Cardiology | Article

CMR imaging superior to SPECT for diagnosing coronary heart disease

Abstract

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MedWire News: Cardiac magnetic resonance (CMR) imaging is superior to single-photon emission computed tomography (SPECT) for diagnosing coronary heart disease (CHD), a study in The Lancet suggests.

The Cardiovascular magnetic resonance and single-photon emission computed tomography for diagnosis of coronary heart disease (CE-MARC) trial is the largest, real-world evaluation of CMR to date, say study authors John Greenwood (University of Leeds, UK) and colleagues.

"The findings of CE-MARC support the wider adoption of CMR for the diagnosis and management of stable CHD patients," they write.

The study involved 752 patients with suspected angina pectoris and at least one major cardiovascular risk factor determined by a cardiologist. Each patient underwent CMR, SPECT, and invasive X-ray coronary angiography, which was the reference standard for the study.

The CMR test was parametric and consisted of rest and adenosine stress perfusion, cine imaging, late gadolinium enhancement, and MR coronary angiography. The SPECT tests included gated adenosine stress and rest SPECT with technetium (99mTc) tetrofosmin.

Overall, 39% of patients had significant CHD as identified by X-ray angiography.

For CMR, the sensitivity was 86.5%, specificity 83.4%, positive predictive value 77.2%, and negative predictive value 90.5%.

On the other hand, the sensitivity of SPECT was 66.5%, specificity 82.6%, positive predictive value 71.4%, and negative predictive value 79.1%.

The sensitivity and negative predictive value of CMR and SPECT differed significantly (p<0.0001 for both), but the specificity and positive predictive value did not.

Of note, stress perfusion CMR was more diagnostically accurate than SPECT even when adjusting for the angiographic cutoff value used for severity of clinically significant stenosis (≥50% or 70%; p<0.0001).

The authors say that their findings support the inclusion of CMR in evidence-based clinical management guidelines.

In a related commentary, Robert Bonow (Northwestern University, Chicago, Illinois, USA) says: "Whether CMR will supplant SPECT or other established tests, such as stress echocardiography, for routine diagnostic purposes is uncertain."

"Enhanced diagnostic accuracy of CMR must be balanced against availability and cost-effectiveness, and there is a need for evidence of measurable improvements in patient outcomes."

He concludes: "Research is now sorely needed to show that the appropriate use of these resources can further improve patient outcomes."

By Piriya Mahendra

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