Cardiac CT with Somatom Definition Image source: Siemens Healthcare

The use of coronary CT angiography (CCTA) for diagnosis and risk assessment in patients with low or intermediate risk or pretest probability for coronary artery disease (CAD) was viewed favorably, whereas testing in high-risk patients, routine repeat testing and general screening in certain clinical scenarios were viewed less favorably in a multi-society appropriate use criteria document published online Oct. 25 in the Journal of the American College of Cardiology.

The report, written by the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular CT, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the Society for Cardiovascular Angiography and Interventions and the Society for Cardiovascular MR, also suggests that the use of non-contrast CT for calcium scoring is appropriate within intermediate- and selected low-risk patients.

The criteria, which the authors said would “have an impact on physician decision making, performance and reimbursement policy, as well as “help guide future research,” outline the appropriate applications of CCTA and are within the category of cardiac structural and functional evaluation.

In scoring the indications, Allen J. Taylor, MD, from the Washington Hospital Center in Washington, D.C., and colleagues said that the following probabilities, as calculated from various available algorithms, should be applied:

• Low pretest probability: 10 percent pretest probability of CAD;
• Intermediate pretest probability: Between 10 percent and 90 percent pretest probability of CAD; and
• High pretest probability: 90 percent pretest probability of CAD.

 
This document is an update to the original appropriateness criteria for CCTA published in 2006. However, the authors said that a direct comparison to the 2006 document is “difficult” because of the many changes in the number and wording of clinical scenarios.

In summary:

• Thirty-one indications were carried forward from the 2006 document, including prior ratings where 10 were appropriate, 10 were uncertain and 11 were inappropriate. Among these, eight shifted up one category from either uncertain to appropriate (Indications 1 [intermediate], 6 [low], 10 [intermediate], 39, 49, 54) or from inappropriate to uncertain (Indications 2 [high], 42 [more than five years]). The other 23 indications are unchanged appropriate use ratings.
• One area of expansion compared with the 2006 criteria involves symptomatic patients without known heart disease. CCTA was felt to be appropriate primarily for situations involving a low or intermediate pretest probability of obstructive CAD. Scenarios involving high-probability CAD patients were rated as uncertain with the exceptions of a patient with an interpretable ECG who was able to exercise, and for definite MI.
• Non-contrast CT calcium scoring was judged as appropriate for intermediate coronary heart disease (CHD) risk patients, and for the specific subset of low-risk patients in whom a family history of premature CHD was present. Intermediate risk was defined as a 10-year risk of between 10 and 20 percent, although individual patient exceptions to a broadened intermediate risk range of 6 to 20 percent were recognized for certain patient subsets with generally low absolute risk but high relative risk (younger men and women). Screening asymptomatic patients using CCTA was considered inappropriate, as was repeat coronary calcium testing. Repeat CCTA in asymptomatic patients or patients with stable symptoms with prior test results was broadly considered inappropriate.
• Within heart failure, CCTA was appropriate or uncertain as a test across both normal (new to this document) and abnormal left ventricular ejection fraction (LVEF), although the only appropriate scenarios were with reduced LVEF with low or intermediate pretest CAD probability.
• As part of the preoperative evaluation, CCTA was viewed as a potential option among patients undergoing heart surgery for noncoronary indications (e.g., valve replacement surgery or atrial septal defect closure) when the pretest CAD risk was either intermediate (appropriate) or low (uncertain). In comparison, there were no appropriate indications for CCTA as part of the preoperative evaluation for noncardiac surgery.
• The evaluation of coronary stents was considered as a function of patient symptom status, time from revascularization and stent size. Only with larger stents (> 3 mm in diameter) after long periods of time (> two years) was stent imaging considered uncertain, and only with left main stents was imaging of stents considered appropriate.
• The strength of CCTA is the evaluation of cardiac structure and function. Appropriate indications include coronary anomalies, congenital heart disease, right ventricular function evaluation, LVEF evaluation when images from other techniques are inadequate or evaluation of prosthetic heart valves. New to this document is the use of CCTA for evaluation of myocardial viability when other modalities are inadequate or contraindicated (uncertain), and in suspected arrhythmogenic right ventricular dysplasia (appropriate).
• CCTA use was appropriate prior to electrophysiological procedures for anatomic mapping, or prior to repeat sternotomy in preoperative cardiac surgery.
• There was disagreement on the panel in two clinical scenarios: CAD detection in the setting of a low pretest probability for CAD when the ECG is interpretable and the patient is able to exercise (Indication 1); and preoperative coronary assessment prior to noncoronary cardiac surgery in the setting of a low pretest probability for CAD (Indication 30). Both of these indications were ranked as uncertain.

Taylor and colleagues concluded that this document represents the current understanding of the net clinical benefit of CCTA with respect to the balance between benefit and risk to the patient as assessed under the appropriate use criteria methodology. “It is intended to provide a practical guide and perspective to clinicians and patients when considering CCT imaging and promote more appropriate test utilization including avoidance of either under- or overutilization,” they wrote.

The full text of this report was published online Oct. 25 in the Journal of the American College of Cardiology. The document also will appear in the November issue of the journal, when it will also be co-published in Circulation and the Journal of Cardiovascular Computed Tomography.