MR imaging spots silent but deadly cardiac conditions

May 1, 2007

Not all those who suffer heart attacks have typical symptoms. Many people, including the elderly, those with renal disease, and women, are at risk of having a silent myocardial infarction.

Not all those who suffer heart attacks have typical symptoms. Many people, including the elderly, those with renal disease, and women, are at risk of having a silent myocardial infarction. People with diabetes, in particular, are among those at highest risk of experiencing a silent MI. Now there is a clinical MRI technique that can identify abnormal myocardium, which signifies a high-risk profile, in diabetic patients.

Using late-enhancement cardiac MR in 133 patients, Harvard University researchers found the technique detected scarred myocardial tissue previously undiagnosed by left ventricular ejection fraction and ECG testing. They also found that those with the abnormal myocardium were more likely to experience other adverse cardiac events, including heart attack, unstable angina, congestive heart failure, and death. Senior investigator Dr. Raymond Kwong, codirector of cardiac MRI and CT at Brigham and Women's Hospital in Boston, presented the study at the 2007 Society for Cardiac Magnetic Resonance meeting in Rome.

Cardiac MR, however, will complement, not replace, current diagnostic tests, Kwong said. Clinical centers in Europe, Asia, and South America already apply the technique, which does not require a new scanner, only upgrades to existing hardware. A steep learning curve might be the only significant limitation. Kwong added that a large-scale trial would be needed to determine whether the technique should be used to screen patients and refer them for further treatment.

In another study presented at the SCMR meeting, Dr. W. Gregory Hundley and colleagues at Wake Forest University in North Carolina found that dobutamine stress perfusion MRI performed on patients with reduced heart function can identify who will die of a heart attack.

They assessed 240 consecutive patients who had a left ventricular ejection fraction lesser than or equal to 55% and were poor candidates for other types of cardiac stress testing. The researchers found a significant link between an increase in the wall motion score index of some patients and their likelihood of myocardial infarction and death. The predictive value was greater when the wall motion index was greater than or equal to 1.7 but lesser than or equal to 2.4.

The procedure might prove useful in clinical practice, particularly for patients who cannot be imaged well with existing procedures, Hundley said.