JACC: DS-MRI predicts cardiac arrest, revascularization

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High-dose dobutamine stress MRI (DS-MRI) can be used to accurately identify patients at high risk for cardiac death and heart attack, a study published Oct. 5 in the Journal of the American College of Cardiology found. Patients with wall motion abnormalities (WMA) and perfusion deficits were significantly more likely to experience cardiac death, heart attack or revascularization, according to the study.

DS-MRI is a standard procedure for detecting coronary artery disease (CAD), but only minimal evidence exists as to the prognostic value of DS-MRI of WMA and perfusion assessment in detecting ischemia. “Assessment of long-term outcome of DS-MRI is important because this test may identify both high-risk patients who would benefit from invasive diagnostic and therapy, and lower-risk patients in whom additional procedures and intensive medical follow-up are not required,” Grigorious Korosoglou, MD, of the department of cardiology at the University of Heidelberg, Germany, and co-authors wrote.

The researchers assessed 1.5-T whole-body DS-MRI results for 1,493 consecutive patients suspected of having, or already diagnosed with, CAD. Wall motion and perfusion were assessed at baseline and under stress, and “hard events” (cardiac death and myocardial infarction), as well as revascularization were followed for an average of two years. The study also recorded common clinical indicators of CAD such as renal function under DS-MRI, diagnosis of diabetes mellitus and family history.

Fifty-three hard cardiac events were observed in the study, 14 cardiac deaths and 39 nonfatal heart attacks. Eighty-five patients also underwent “late” revascularization; an additional 158 patients underwent “early” revascularization within 90 days of the DS-MR, which the authors attributed to the study’s stress tests rather than pre-existing conditions and therefore were excluded from the results.  

Patients with inducible WMA were 33 percent more likely to experience hard cardiac events and 40 percent more likely to undergo revascularization within a period of four years. Similarly, patients with inducible perfusion deficits were 25 percent more likely to experience hard cardiac events and over 40 percent more likely to require revascularization within four years of the DS-MRI. Patients with normal DS-MRI (WMA- and perfusion deficit-free) readings had very low rates of cardiac events (one cardiac death and four heart attacks out of 1,193 patients) and revascularization. All results were statistically significant.

While both perfusion deficits and WMA significantly increased patients’ hazard ratios for cardiac events and revascularization individually, perfusion deficits did not significantly increase patients’ likelihoods of experiencing cardiac events or revascularization if they were complemented by WMA. In addition, patients at high-risk for CAD before DS-MRI (defined by factors such as poor renal function, current or prior smoking, diabetes mellitus, older age and family history) were 5 percent more likely to experience cardiac events and revascularization, with or without WMA presence. Low to intermediate risk CAD patients only faced increased risks (5 percent higher) of cardiac events when WMA or perfusion deficits were discovered under DS-MRI.

“In agreement with previous studies,” the authors commented, “the assessment of wall motion during stress was the most powerful index, yielding the highest hazard ratio for subsequent hard events. Furthermore, the presence of inducible WMA added value to risk stratification of patients with and without inducible perfusion deficits.”

Korosoglou and colleagues did note several limitations to their study. “Patterns of left ventricle geometric remodeling and the presence of delayed enhancement were not systematically analyzed,” the authors said, which may have weakened the ability of left ventricle (LV) impairment to predict outcomes beyond ejection fraction. The authors also acknowledged that motion artifacts and lower viewing resolution with increasing heartbeats should be considered when interpreting their results.

“The assessment of wall motion and perfusion during stress testing can accurately identify patients with positive findings who are at increased risk for cardiac events, and separate them from those with normal findings who are at much lower risk,” the authors concluded.