Predicting Heart Attack Risk with CT Angiography

Coronary computed tomography angiography (CCTA) is an effective tool for determining the risk of myocardial infarctions and other abnormal cardiac events in patients with suspected coronary artery disease (CAD) but no treatable risk factors, such as high blood pressure or high cholesterol.

“CCTA should be considered as an appropriate first-line test for patients with atypical chest pain and suspected but not confirmed coronary artery disease,” said the study’s lead author, Jonathon Leipsic, MD, FRCPC, from the University of British Columbia (Vancouver, BC, Canada).

Treatment for heart disease typically involves tackling modifiable cardiovascular risk factors such as high blood pressure, elevated cholesterol, diabetes, and smoking. However, some risk factors, such as family history, are not modifiable, and no risk models exist to help guide clinicians to identify those symptomatic patients without cardiac risk factors who are at an increased risk of death and myocardial infarction. “This scenario, where patients are symptomatic but have no cardiac risk factors, comes up often in clinical practice,” Dr. Leipsic said. “We lack a good tool to stratify these patients into risk groups.”

CCTA is a noninvasive test that has shown high accuracy for the diagnosis or exclusion of coronary artery disease in individuals. However, referral for patients with suspected coronary artery disease is frequently based on clinical risk factor scoring. Less is known about the prognostic benefits of CCTA in individuals with no medically modifiable risk factors.

In the first study of its sort, published online February 2013 in the journal Radiology, Dr. Leipsic and colleagues correlated CCTA results with the risk of major adverse cardiac events in 5,262 patients with suspected coronary artery disease but no medically modifiable risk factors. They culled the data from the Coronary CT Angiography Evaluation For Clinical Outcomes: An International Multicenter (CONFIRM) registry.

After a median follow-up of 2.3 years, 104 patients had experienced a major adverse cardiovascular event. The researchers identified a high occurrence of CAD in the study group, in spite of the lack of modifiable risk factors. More than 25% of the patients had non-obstructive disease or disease related to the accumulation of plaque in the arteries, and another 12% had obstructive disease with a greater than 50% narrowing in a coronary artery. “We found that patients with narrowing of the coronary arteries on CT had a much higher risk of an adverse cardiac event,” Dr. Leipsic said. “This was true even for those without a family history of heart disease.”

Both asymptomatic and symptomatic patients with obstructive disease faced an increased risk for a major cardiac event. Contrarily, the absence of CAD on CCTA was associated with a very low risk of a major event.

The findings, according to the investigators, emphasize the need for improvement in the evaluation of individuals who may be overlooked by conventional techniques of CAD assessment. “If a patient shows up with vague symptoms and no medically modifiable risk factors, doctors often dismiss them or do a treadmill test, which won’t identify atherosclerosis and only has a modest sensitivity for detecting obstructive disease,” Dr. Leipsic said.

CCTA could help address this problem, Dr. Leipsic added, by helping to detect or rule out coronary artery disease and identifying those who may be helped with more intensive therapy. The researchers continue to examine the CONFIRM data with the goal of further clarifying the association between plaque and myocardial infarctions and the longer-term outlook for patients with coronary artery disease.

“We are now collecting data to determine the prognostic value of CCTA after five years or more of follow-up, which will be very important for the field,” Dr. Leipsic stated.

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University of British Columbia