CMR 'may be preferable' to SPECT for CHD prognosis

By Eleanor McDermid

Long-term follow-up of the CE-MARC study suggests that cardiovascular magnetic resonance (CMR) could be a better predictor of cardiovascular events than single-photon emission computed tomography (SPECT) in patients with coronary heart disease (CHD).

The original CE-MARC (Clinical Evaluation of MAgnetic Resonance imaging in Coronary heart disease) findings showed that the two techniques had equivalent diagnostic power.

For the latest analysis, published in the Annals of Internal Medicine, the researchers monitored 628 study participants with suspected stable angina who had undergone both diagnostic techniques, plus the reference test of X-ray angiography. During 5 years of follow-up, 16.6% had at least one major adverse cardiovascular event (MACE).

"Hard" clinical endpoints, defined as cardiovascular death and nonfatal myocardial infarction/acute coronary syndrome, occurred in a similar proportion of patients with abnormal findings on CMR and SPECT, at 7.9% and 7.4%, respectively. And the same was true of the broader MACE outcome, which also included unscheduled coronary revascularisation and hospitalisation for any cardiovascular cause, at 25.2% and 21.2%, respectively.

However, after accounting for variables including age, gender, diabetes, smoking status and hypertension, only CMR significantly predicted MACEs within 5 years, with abnormal findings raising the risk 2.3-fold, compared with a nonsignificant 1.4-fold for an abnormal SPECT result.

And CMR continued to be a significant predictor after accounting for angiography findings and initial treatment strategy, report John Greenwood (University of Leeds, UK) and study co-authors.

Of note, normal findings with either technique were associated with a low rate of adverse outcomes, at 1.4% and 2.5% for hard endpoints after CMR and SPECT, respectively, and a corresponding 10.0% and 14.1% for MACEs.

In a linked editorial, Myriam Hunink (Erasmus University Medical Center, Rotterdam, the Netherlands) and Kirsten Fleischmann (University of California, San Francisco, USA) say this latter finding "is reassuring and has important prognostic value."

The editorialists highlight the difficulties in disentangling the effects of prognosis, treatment and other factors in an observational study. However, they believe that the current findings, together with research showing equivalent cost-effectiveness for the two techniques, "suggest that, if available, CMR may be preferable to SPECT for evaluation of patients with suspected CHD."

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