Diagnostic Imaging
June 2004

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MR and echocardiography race for cardiac supremacy

Despite echo's five decades of success, it may not stand up to MR's strong emerging data

Both cardiac MR and echocardiography can stake a claim as the gold standard for noninvasive evaluation of coronary disease, but for somewhat different reasons, according to proponents of the two imaging modalities.

For assessment of ventricular function, viability, coronary artery integrity, and identification of inducible ischemia, cardiac MR is exemplary, said Dr. Warren Manning, chief of noninvasive cardiac imaging at Beth Israel Deaconess Medical Center. Manning, who spoke during a debate at the American College of Cardiology meeting in March, chided his debate opponent by contending that an average MR looks like a great echo.

Pretty pictures do not demonstrate superiority, countered Dr. A. Jamil Tajik, a professor of medicine and consultant cardiologist at the Mayo Clinic in Rochester, MN. Echocardiography's outcomes data spanning 50 years have withstood the test of time, he said.

According to Manning, 2D and M-mode echo are inferior to volumetric MR techniques in normal and myopathic hearts. The inferiority relates to the geometric assumptions often used in echo, not to some specific trait of MR. In fact, some studies suggest that 3D echo offers accuracy comparable to that of cardiac MR, he said.

Areas in which cardiac MR equals or surpasses echo include dobutamine stress tests, perfusion to detect coronary disease, assessment of regional wall motion of the left ventricle, distinguishing of viable myocardium from nonviable tissue, and determination of the level of functional recovery after revascularization, Manning said. Cardiac MR also offers the potential to evaluate the coronary arteries.

But echocardiography's value in diagnosing coronary disease has been validated in more than 50 studies involving more than 20,000 patients, Tajik said. In patients with chronic ischemic heart disease, shortened mitral deceleration time on echo correlates with a low likelihood of functional improvement after revascularization. Both 2D and 3D echo have proved useful for evaluating the challenging patient population with ischemic mitral regurgitation.

"The role of echo in coronary disease in the acute setting is unsurpassable," Tajik said. "In patients with arrhythmias or chronic ischemic left ventricular dysfunction, echo is unsurpassed in assessing structure, function, and hemodynamics."

While Tajik lauded the portability and low cost of echo, Manning touted MR's ability to conduct a complete, multifaceted cardiac evaluation in less than an hour. He also dispelled the notion that cardiac MR is expensive, saying that the cost falls midway between echo and nuclear studies.

But with the last word, Tajik said that Manning's vision of MR as a portable, inexpensive imaging modality that provides immediate information about numerous aspects of patient status is still just a dream.

"And because of that, echo will remain the heart of cardiology for now and for the near future," he said.