JACC: CCTA proves its merit as predictor in meta-analysis

Calcified and noncalcified plaque by CCTA. Source: Fabian Bamberg, MD, University of Munich

The presence and extent of coronary artery disease detected during coronary CT angiography (CCTA) are strong, independent predictors of cardiovascular events, according to a meta-analysis published June 14 in the Journal of the American College of Cardiology. In addition, the meta-analysis provided data to direct which finding should be included in standard CCTA reports.

Currently, the development of clinical practice guidelines focused on CCTA has been constrained by the lack of robust outcome data, wrote Fabian Bamberg, MD, MPH, of the department of clinical radiology at Ludwig-Maximilians University in Munich, and colleagues. In addition, despite the increasing volume of data suggesting that the presence and severity of CCTA-detected coronary artery disease is linked with risk for future cardiovascular events, uncertainty about individual risk estimates has stalled development of actual risk estimates associated with specific findings.

“[I]t is necessary to appropriately design future outcome studies including risk modification in prospective, randomized intervention trials and consideration of the public health impact of an increased use of noninvasive cardiac imaging using coronary CTA,” wrote Bamberg.

Bamberg and colleagues completed a systematic review of studies that analyzed the prognostic value of CCTA and located 11 cohort studies of more than 100 subjects with follow-up of at least one year.

The researchers focused on assessing the relationship between a CCTA finding of significant coronary stenosis (>50 percent luminal narrowing) and a combined cardiovascular endpoint. Secondary predictors were presence of any atherosclerotic plaque, presence of significant left main stenosis and the risk associated with each coronary segment containing plaque, shared the researchers.

The 11 studies included 7,335 subjects (average age 59.1 years, 62.8 percent male) with follow-up ranging between 14 and 78 months.

The researchers estimated a 10-fold higher risk of outcome events (cardiovascular death, nonfatal myocardial infarction, unstable angina requiring hospitalization and revascularizations) among patients with CCTA-detected coronary stenosis compared with subjects without coronary stenosis.

There was, however, substantial heterogeneity with respect to risk prediction based on choice of endpoints, classification of CT findings and age of the study population.

Specifically, the researchers noted higher risk associated with CT studies that included revascularization. In fact, the annualized event rate was 5 percent for all studies, but it fell to 1 percent when it focused on death, nonfatal myocardial infarction and unstable angina (i.e., excluding revascularization). This led the researchers to recommend that revascularization be reported as an outcome of CCTA utilization and efficiency rather than efficacy and effectiveness.

Analysis of the three studies that included the incremental value of CCTA beyond coronary calcification showed that the association between the presence of significant coronary stenosis or any plaque and cardiovascular events remained highly significant after adjustment for coronary calcium, according to Bamberg and colleagues.

In addition, the researchers noted that subjects with any plaque detected by CT were at approximately 4.5-fold risk for events compared with subjects without plaque detected. Each segment containing detectable plaque is associated with 23 percent higher risk for adverse outcomes.

Bamberg and colleagues determined that several CT findings are linked with worse outcomes and recommended that they be included as standard report measures. These are:

• The presence of at least one coronary artery stenosis exceeding >50 percent diameter stenosis per patient;
• The number of coronary segments containing at least one coronary artery stenosis exceeding >50 percent diameter;
• Left main coronary artery disease;
• The presence of any detectable atherosclerotic plaque (regardless of severity) per patient; and
• The number of segments containing nonobstructive plaque, calcified, noncalcified and mixed plaque.

In addition, the researchers emphasized the need for a large prospective study focusing on clinically more relevant endpoints, i.e. death, myocardial infarction and unstable angina rather than revascularizations. They suggested that the ongoing 10,000 patient PROMISE (PROspective Multicenter Imaging Study for the Evaluation of chest pain) trial fills this gap.

The results indicated that CCTA "may provide incremental prognostic information beyond the analysis of coronary calcium,” wrote Bamberg, but confirming this hypothesis requires larger, dedicated studies.