Clinical evidence secures reprieve for coronary CTA

Pending clinical trial results played a pivotal role in the Centers for Medicare and Medicaid Services' decision in March to set aside plans to establish a national payment policy for outpatient multislice coronary CT angiography. Other published trials advanced our understanding of how nuclear cardiology, echocardiography, and cardiac MRI fit in evolving diagnostic practice.

The March decision rejected an advisory committee recommendation to demand more evidence to justify reimbursement for coronary CT angiography. A "Coverage with Evidence Development" requirement would have limited payment to a few facilities that participate in CMS-approved clinical trials.

The CMS deliberations were pivotal, said Dr. Daniel Berman, president-elect of the Society of Cardiac Computed Tomography.

"This was a monumental decision," he said in an interview. "If it had gone the way it was being suggested, there would have been a marked slowdown in the development of this very promising new field.

Unpublished and newly published research figured prominently in the analysis published with CMS's final decision that rejected the recommendation. The report, for example, cited findings from a Dutch study of 64-slice coronary CTA performed on 104 nonconsecutive patients with either unstable angina or non-ST elevation myocardial infarction (Heart 2007;93:1386-1392). Though 16% of the coronary segments were excluded because of poor visualization, Dr. Willem B. Meijboom and colleagues at the Thoraxcenter in Rotterdam found on a perpatient basis that the test was 100% sensitive and 75% specific for detecting significant coronary stenoses.

Conducted by a former critic of coronary calcium scoring, the MESA trial demonstrated that calcium scoring performed on MSCT studies is superior to the Framingham risk scores for predicting cardiac events. The findings were consistent for African American, Caucasian, Chinese, and Hispanic populations. The trial also demonstrated that any coronary calcium score higher than zero is associated with increased risk.

"While it remains to be determined which individuals benefit most from such testing, this study provides further and very strong evidence that imaging the actual substrate of cardiovascular events (atherosclerotic plaque) al­lows for more accurate risk prediction than traditional risk factors," said Dr. Stephan Achenbach, a professor of internal medicine at the University of Erlangen in Germany.

Cardiac CT's emergence as a mainstream tool has led researchers to reconsider how nuclear medicine, echocardiography, cardiac MR, and x-ray angiography complement one another.

PET may play a larger role in cardiology, perhaps as a replacement in some instances for the stress-rest SPECT protocol that Berman helped develop in the 1990s at Cedars-Sinai Medical Center in Los Angeles.

New SPECT cameras are improving the sensitivity and speed of myo­cardial perfusion imaging. A review in the Journal of the American College of Cardiology Imaging (2008,1:156-163) found that high-speed SPECT was up to eight times more sensitive than conventional cameras for myocardial perfusion imaging. More journal work is expected to explore these themes as more high-sensitivity SPECT devices are installed, according to Dr. Art Stillman, a professor of medicine and biomedical engineering at Emory University.

A recent study by Dr. Uchechukwu K. Sampson from Dr. Marcelo Di Carli's group at Brigham and Women's Hospital established that the sensitivity of rubidium-92 PET/CT for the presence of single- and multivessel coronary artery disease was 92% and 95%, respectively. The results suggest that PET will be most appropriate for patients who have an intermediate risk of coronary disease and are ill-suited for CT imaging, Berman said.

At the 2008 American College of Cardiology meeting, Dr. Rasmus Mogelvang, a cardiologist at Gentofte Hospital in Copenhagen, demonstrated that echocardiography reliably predicted cardiac-related mortality over a three-year period when it accounts for both systolic and diastolic measures of ventricular performance. The findings were drawn from echo tests performed on 1011 healthy volunteers enrolled in the Fourth Copenhagen City Heart Study in Denmark.

A cardiac MRI study presented at the 2008 Society for Cardiovascular Magnetic Resonance meeting added to a growing concerns about the selection of patients for revascularization. Dr. Joseph Selvanayagam, a CMR researcher at Flinders University in Adelaide, Australia, found that 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. The study was supervised by Dr. Stefan Neubauer while Selvanayagam practiced at Oxford University in 2007.