Report from SCMR: Delayed enhancement predicts post−revascularization procedure risk

A cardiac MRI study measuring the risk of death and myocardial infarction from surgically induced myocardial damage bolsters a growing argument encouraging clinicians to use caution when deciding to revascularize asymptomatic heart patients.

Patients with evidence of new myocardial hyperenhancement after revascularization have a threefold higher risk of death, infarction, or other major cardiovascular events in the three years after surgery than patients without such damage, according to a study led by Dr. Joseph Selvanayagam, a CMR researcher at Flinders University School of Medicine in Adelaide, Australia. The study was supervised by Dr. Stefan Neubauer while Selvanayagam practiced at Oxford University Center for Clinical Magnetic Research in 2007.

Selvanayagam's investigation is an extension of his previous work. It found that about three of 10 patients who undergo complex percutaneous coronary interventions (PCI) show evidence of surgically related myocardial hyperenhancement on delayed-enhancement CMR (Circulation 2005;111(8):1027-1032). Other studies suggest that up to half of all revascularization procedures may produce some damage to the myocardium, he said at the 2008 Society for Cardiovascular Magnetic Resonance meeting in Los Angeles.

This evidence follows the 2007 publication of the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial. That randomized investigation involving 2287 patients found that PCI did not reduce the risk of death, myocardial infarction, or other major cardiovascular events when added to noninvasive therapies for patients with stable coronary artery disease (NEJM 2007;356:1503-1516). It led some cardiologists to recommend against angioplasty or bypass surgery for such patients.

Selvanayagam based his new findings on DE-CMR and troponin enzyme tests performed the day before and the day after complex PCI for 93 patients and coronary artery bypass graft for 65 patients. About 88% of the patients had stable angina, and myocardial ischemia was cited as the primary indication for the interventions.

A comparison of pre- and postsurgical DE-CMR identified a new zone of myocardial hyperenhancement in 32% of patients. Hyperenhancement is a well-established indicator of necrotic myocardial tissue. The median mass of the new lesion was 5 g.

Follow-up surveys performed an average of three years later found that 27 patients (18%) achieved a primary endpoint (death from a cardiac-related event, nonfatal MI, prolonged ventricular arrhythmia leading to implantation of a cardioverter defibrillator, or hospitalization from unstable angina or heart failure). Twelve patients (8%) achieved the secondary endpoint (death from a noncardiac condition, nonfatal MI, or ventricular arrhythmia).

Patients with new postsurgical myocardial hyperenhancement were about 3.1 times more susceptible to cardiac death, nonfatal infarction, or other major event than patients without evidence of surgically related myocardial damage, Selvanayagam said. Neither troponin enzymes nor left ventricular functional measurements produced statistically significant findings.

Selvanayagam also found a correlation between the mass of the new lesions and clinical outcomes. Each gram of hyperenhanced tissue translated into a 10% increase in the probability that the patient would experience an adverse cardiac event, he said.

In the context of the COURAGE trial, Selvanayagam noted that his results underscore the risks involved in performing revascularization procedures on patients with stable coronary disease.

"The increased risk of future clinical events should be taken into consideration when patients are considered for coronary revascularization," he said. "You have to bear in mind the trade-off between the luminal gain from revascularization versus the myonecrosis related to revascularization."

For more information from the Diagnostic Imaging archives:

Delayed-enhancement coronary artery imaging tracks vascular inflammation changes in stable and unstable CAD

DE-MRI depicts postablation scar

Report from SCMR: DE-CMR stratifies risk for dilated cardiomyopathy patients