Meta-analysis validates cardiac MR’s prognostic value

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 - Siemens Sensation CT

Pharmacologic stress cardiac MR offers excellent prognostic risk stratification of patients with known or suspected coronary artery disease (CAD), according to a meta-analysis published in the Aug. 27 issue of the Journal of the American College of Cardiology. While questioning its clinical utility, editorial writers gave it a thumbs up as a prognostic tool.

Cardiac MR (CMR) already has shown its worth as a diagnostic tool for detecting CAD, wrote Michael J. Lipinski, MD, PhD, of the University of Virginia Health System in Charlottesville, Va., and colleagues. Several small and single-center studies also have suggested it may be useful for stratifying low- and high-risk patients with known or suspected CAD. The authors undertook a review and meta-analysis of prognostic CMR studies to add clarity to the issue.

“Prognostic validation of stress CMR is critical because a negative stress CMR can be reassuring that the patient has a very low risk for major adverse cardiovascular events (MACE),” they wrote. “Alternatively, patients with stress-induced wall motion abnormalities, abnormal perfusion, and/or LGE [late gadolinium enhancement] are at higher risk of MACE.”

They included 19 peer-reviewed studies selected through a search of Cochrane Central, PubMed and meta-Register of Controlled Trials. The studies had a mean follow-up of 32 months and included a total of 11,636 patients. Fourteen used vasodilator stress, four dobutamine stress and one both vasodilator and dobutamine stress.

LGE was seen in 29 percent of patients, and those with evidence of LGE had worse outcomes compared to those without (odds ratio of 3.82). Ischemia was present in 32 percent of patients, with a higher incidence of MI (odds ratio of 7.7).

“The data demonstrate that patients with a stress CMR negative for evidence of ischemia have less than 1 percent AER [annualized event rate] of either cardiovascular death or nonfatal MI, whereas patients with ischemia on stress CMR have a 5 percent AER of either cardiovascular death or nonfatal MI,” Lipinski et al wrote. “Furthermore, there was no difference between vasodilator stress CMR and dobutamine stress CMR in terms of prognostic characteristics.”

The authors proposed that the findings give weight to the use of CMR for stratifying patients at low- and high-risk for MACE and make CMR “an excellent alternative to stress nuclear myocardial perfusion imaging and stress echocardiography in patients who cannot exercise. This is especially true given the excellent diagnostic characteristics of stress CMR for CAD.”

Raymond H. Chan, MD, MPH, and Warren J. Manning, MD, both of Beth Israel Deaconess Medical Center in Boston, agreed that the meta-analysis findings support CMR’s role as a prognostic tool but added it was still unclear how the data would guide patient management. They listed study limitations, including heterogeneity of study populations, a mixture of prospective and retrospective studies, variable definitions of terms and questions about generalizability.

They acknowledged that CMR can provide a comprehensive cardiovascular evaluation and recommended further studies to clarify its clinical utility. “One cannot deny the attractiveness of a test that is free of ionizing radiation, accurate, and potentially cost-effective,” they concluded.