ASNC: Patient selection is 'cornerstone' of nuclear card

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DENVER—When performing nuclear imaging studies, it is important to balance benefits against potential risks, however, it is most imperative to ensure that only appropriate patients are being imaged, George A. Beller, MD, a cardiologist at the University of Virginia Health System in Charlottesville, said during a presentation Sept. 10 at the 16th annual American Society of Nuclear Cardiology (ASNC) scientific session.

Numerous factors must be considered when selecting the appropriate stress test modality, Beller offered. These factors include accuracy of the test (sensitivity and specificity); pre-test probability of coronary artery disease (CAD); safety (contrast and radiation dose); as well as cost effectiveness.

Beller outlined results of a previous study that showed that of the 655,614 patients enrolled who underwent at least one imaging procedure per year, 24 percent had moderate to fairly high radiation exposure.

“We must think about this exposure more and more as we select types of stress tests and radionuclide protocols,” Beller said. “While we must maintain accuracy, at the same time, we must also reduce radiation exposure.”

An additional study outlined that patients with a greater number of risk factors see higher event rates during normal exercise SPECT tests. For 124 patients with no risk factors, event rates were 0.9 per year; for patients with more than three CAD risk factors, the event rate was 1.7 per year.

Beller also offered that in post-stress SPECT imaging, of the patients who received abnormal scans, revascularized patients had significantly better outcomes than patients who underwent optimal medical therapy (OMT). Cardiac death rates were 4.6 percent for patients treated with OMT and 1.3 percent for revascularization. This is where individualizing patient treatment becomes important to improve outcomes, Beller said.

Additionally, Beller noted that SPECT imaging had an incremental value over ECG echo, lab exam and clinical markups, as well as coronary angiography.

“Stress myocardial perfusion imaging [MPI] with SPECT or PET provides clinically useful prognostic information for patients with suspected or known CAD,” Beller offered. “PET MPI offers a higher value for risk assessment.”

Beller concluded that the radiation exposure must always be balanced against the benefits of imaging. However, “for the noninvasive assessment of prognosis, the 'cornerstone' of nuclear cardiology, only appropriate patients should be imaged, stress only imaging in low to intermediate risk patients,” Beller said. “Start with ECG alone for low-risk patients who have good functional capacity and make sure to employ the best possible strategy for each individual patient population.”