Report from SCMR: Cardiac MR identifies patients who require aortic valve surgery

Oxford University researchers have established that aortic regurgitation fraction, measured with cardiac MR, accurately singles out patients who need aortic valve replacement surgery.

Patients with aortic regurgitation pose a challenge, especially when they are asymptomatic, said Dr. Saul G. Myerson, during the opening session of the 2008 Society for Cardiovascular Magnetic Resonance meeting in Los Angeles.

Physicians have traditionally relied on physical signs and symptoms to guide surgical decision making. For some patients, measurements of excess left ventricular dilation or dysfunction are appropriate, but they force the clinician into a balancing act. Left untreated, severe LV dilation can lead to death in some patients, while it has no effect for years on many others.

"That would mean we would operate on them unnecessarily in some cases," he said.

Aortic regurgitation measurement with echocardiography is difficult, but Myerson and colleagues found that CMR is relatively easy to perform and can be added to the protocol for measuring LV function. Their study examined the clinical utility of the CMR measures and the optimal thresholds to guide therapy.

Fifty aortic regurgitation patients were examined, 33 of them asymptomatic. Their conditions were established with a baseline CMR scan and monitored with annual CMR for up to five years. They were compared with 17 surgical patients, who exhibited conventional physical indications for a surgical interventional. The surgical group received only a baseline CMR scan before surgery.

Results showed that regurgitant fraction was far more able to predict progressive disease than any measure of LV function, Myerson said. No patient with a regurgitant fraction of less than 20% progressed. About 18% of patients with fractions from 21% to 30% progressed, and more than two-thirds of patients with fractions more than 33% went on to surgery. Sensitivity and specificity were 100% and 77%, respectively.

Because of these findings, all patients at or above the 33% threshold were classified as good candidates for immediate valve replacement surgery, Myerson said.

Aortic regurgitation fraction also accurately predicted progression to surgery for the 33 asymptomatic subjects. All 19 patients with values of less than 33% survived more than five years, compared with a 40% survival rates for the 14 women and men with regurgitant fractions of more than 33%.

Myerson expressed confidence in the ability of CMR measurement of aortic regurgitation fraction to separate surgical candidates from patients who qualify for conservative therapy in a timely and accurate way.

"I would suggest that we can start thinking about using these measures to plan which patients would be most appropriate for surgery," he said.

For more information from the Diagnostic Imaging archives:

MRI demonstrates heart morphology and function

Consensus remains elusive for best left ventricle test

Cardiac MR research builds on modality's inherent strengths