Coronary artery CT assesses sudden death risk from all cardiovascular causes

Multislice CT evaluations of coronary artery stenosis can calculate the risk of heart-related death for patients with recently diagnosed coronary artery disease. Results are at least as reliable as those presented by conventional myocardial perfusion SPECT imaging.

A trial conducted by Dr. Tracy Q. Callister, director of the Tennessee Heart and Vascular Institute in Nashville, involved 1138 patients who underwent MSCT coronary angiography for chest pain.

Callister's collaborators included Dr. James Min, director of cardiac CT at New York Presbyterian Hospital, Dr. Daniel Berman, director of nuclear cardiology at Cedars-Sinai Medical Center in Los Angeles, and Leslie J. Shaw, Ph.D., at the Atlanta Cardiovascular Research Institute. Min presented the results in June at the 2007 Stanford Multidetector-Row CT Symposium in San Francisco.

All patients were at least 45 years old. Coronary stenoses were graded as minimal (less than 30%), mild (31% to 49%), moderate (50% to 69%), or severe (more than 70%).

The investigators identified several statistically significant predictors of future mortality from data collected during the MSCT test when they checked on the patients' health status an average of 15.3 months later. They found that 39 subjects had died in the follow-up period. Patients with mild or no coronary artery plaque had a 99.7% chance of surviving, while the survival rates for patients with moderate or severe coronary disease dropped off to 85%.

"There was a stepwise reduction in survival given the number of vessels involved," Min said. "If you have at least moderate or severe plaque in the left main artery, it portends an extremely unfavorable prognostic category for those 15 months."

A similar stepwise decrement for survival was seen for moderate stenosis, with plaque residing in the left main artery leading to the worst results, he said.

The Duke coronary artery disease index, using data from the MSCT studies, generated a highly significant stratification of risk (p<0.0001). The index was valuable for assessing the severity of coronary artery plaque and adjusting the degree of risk to account for the plaque's location in the left main or proximal left anterior descending artery, he said.

With help from Berman and Shaw, the investigators uncovered a strong correlation between MSCT results and assessments of 8000 patients who underwent nuclear stress testing. When matched for the pretest likelihood of significant coronary heart disease, the annual mortality for patients in the CT arm was 1.16% compared with 1.13% for patients in the nuclear perfusion arm, Min said.

The actual death rate was also strongly associated with Duke CAD index jeopardy groups. The highest mortality rates arose patients in the highest risk group then decreased accordingly in the lower risk groups, he said.

"From this, we can conclude that current generation multidetector CT angiography of the coronary arteries possesses strong prognostic value for extent, severity, and location of coronary artery plaque," Min said. "CT and nuclear SPECT imaging possess similar abilities to identify individuals at risk for sudden death."

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