AIM: Low-dose CCTA rivals angio for CAD detection

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Coronary CT angiography study rules out coronary artery disease in a 58-year-old asymptomatic man with multiple cardiovascular risk factors. Image source: U. Joseph Schoepf, Medical University of South Carolina, Charleston

Low-dose coronary CT angiography (CCTA) suggested that the sensitivity of the technique rivals catheter-based angiography and may offer an alternative to invasive angiography in ruling out coronary artery disease in symptomatic patients, according to a meta-analysis of 16 studies published March 15 in Annals of Internal Medicine.

Although 2.3 million CCTA studies are performed annually in the U.S., the noninvasive exam is associated with an effective radiation dose of 12 millisievert [mSv], which has sparked concerns among physicians and patients. Prospective ECG gating, also known as step-and-shoot or sequential mode, cuts dose up to 80 percent by limiting radiation application to a predefined point in the cardiac cycle. However, some physicians have voiced concerns about the potential reduced diagnostic quality of the resulting dataset.

Moritz Wyler von Ballmoos, MD, PhD, MPH, from the department of cardiac surgery at Children’s Hospital Boston, Harvard Medical School in Boston, and colleagues designed the meta-analysis to examine whether or not low-dose CCTA provides sufficient accuracy to be considered for the daily clinical routine.

The meta-analysis focused on 16 studies that compared results of low-dose CCTA with catheter angiography in patients with suspected CAD.

Wyler von Ballmoos and colleagues focused the primary analysis at the patient level, writing that it “is the most relevant analysis from a clinical point of view because it better relates to the clinical purpose of triaging patients.” They also completed analyses at the vessel and segment levels.

Ultimately, the meta-analysis included 2,622 coronary arteries in 11,518 segments in 960 patients. Seven studies used 64-slice scanners; four used dual-source; 64-slice CT; two used 320-slice CT, and each of the following—dual-source; 128-slice; single source; 128-slice; and single source 256-slice CT—accounted for one study.

“On average 2.4 percent of the coronary arterial segments were of nondiagnostic image quality, and one or more segments were nondiagnostic in 9.5 percent of the patients. The average estimated effective radiation dose for low-dose CCTA was 2.7 mSv,” wrote Wyler von Ballmoos.

Researchers used an adaption of the QUADA (Quality Assessment of Diagnostic Accuracy Studies) tool to assess methodological study quality and reported overall satisfactory study quality.

The patient characteristics analysis revealed a mean prevalence of CAD among study participants of 60.1 percent, mean body mass index [BMI] of 26.5 kg/m 2 and a mean age of 63.4 years.

When the researchers reviewed diagnostic performance measurements, they found the patient-level analysis had the highest sensitivity, with a pooled sensitivity of 1.00 and a pooled specificity of 0.89 for low-dose CCTA compared with catheter angiography.

von Ballmoos and colleagues added that low-dose CCTA “seems to be characterized by a very high negative predictive value across a broad spectrum of pretest probabilities for CAD (zero to 80 percent).”

The findings led the researchers to state that “CCTA with prospective ECG gating has a high specificity and an excellent sensitivity for the detection of morphologically significant CAD, compared with catheter angiography.” What’s more, the technique cut radiation dose to 2.7 mSv without sacrificing diagnostic performance, they explained.

Wyler von Ballmoos and colleagues acknowledged a few limitations to the study, explaining that relevant data could not be secured for each analytic level for all studies. Plus, multiple studies originated from a single center, and the overall number of studies included in the meta-analysis was small, so the results of the meta-analysis may not be generalizable.

While pointing out the promising potential of early evidence, the researchers stressed the need for additional studies “to address the potential of low-dose CCTA for use in triage as a means of positively altering management and outcomes in patients with suspected CAD. Thorough analyses of the potential harms of this imaging test are also needed.”