SAN DIEGO, CA — A novel algorithm shows promise in overcoming a major drawback of coronary computed-tomography angiography (CCTA)—artifacts caused by coronary motion in patients with a rapid or irregular heart rate[1].

Dr Daniele E Andreini (Centro Cardiologico Monzino, Milan, Italy) presented preliminary findings from 71 patients of the planned 218 patients in the international Validation of an Intra-cycle CT Motion Correction Algorithm for Diagnostic Accuracy: A Prospective Multicenter Study (VICTORY), in a late-breaking trial session at the Society of Cardiovascular Computed Tomography 2014 Annual Scientific Meeting .

The results agree with those in previously published, single-center studies, he said, which consistently showed that the intracycle motion-correction algorithm—SnapShot Freez4e (GE Healthcare), which received FDA clearance in 2012—improved the quality and interpretability of coronary CT images.

Data analysis of the full study should provide better insight into whether improved image quality will translate into better diagnostic accuracy, Andreini said. This tool might be especially useful when performing CT "in patients who do not receive heart-rate control medications or in whom suitable heart-rate values are not achievable despite the medication," he noted.

By using mathematical modeling and merging two or three data sets, the algorithm is able to eliminate motion artifacts in a patient's coronary CT scan, so that clinicians can better visualize the coronary arteries, moderator Dr Quynh A Truong (Weill Cornell Medical College, New York, NY) commented to heartwire . "It's a novel algorithm that could be used for a scan that typically would be deemed uninterpretable," she noted.

Fast Heart Rates, False-Positive CT Scans

Although CCTA is an effective, noninvasive method to directly visualize the coronary arteries, coronary motion-related artifacts can make it difficult to interpret CT scans. Heart rate plays a crucial role in determining image quality in coronary CT, Andreini said.

"The ideal scenario is a patient with a stable and low heart rate of 65 beats per minute," he noted. "In a patient with a very high heart rate, motion blurring may affect image quality. Motion is one of the most common causes of false positives in coronary CT."

In a single-center study, researchers have reported that the intracycle motion-compensation algorithm improved CCTA image quality, interpretability, and diagnostic accuracy in 36 consecutive patients with severe aortic stenosis[2].

The patients were undergoing CCTA and invasive angiography to be evaluated for transcatheter aortic-valve replacement. Around a third (14 patients) had atrial fibrillation. The patients had a mean heart rate of 71 beats per minute, but this varied by 17 beats during the study.

"Diagnostic accuracy was improved by motion correction, per artery and per segment analysis," Andreini noted.

Similarly, in a study of 120 patients that they presented at last year's European Society of Cardiology Congress, 81% of CT scans were interpretable without the algorithm, but 97% were interpretable with it. For example, in one patient whose heart rate varied from 72 to 87 beats per minute, by using motion correction, researchers were able to identify a severe lesion.

VICTORY for Image Quality

The rationale and design for VICTORY was published last year[3]. The study is comparing the use of a 64-slice CTA scanner (with or without a motion-correction algorithm) vs of the use of invasive coronary angiography to detect and exclude significant coronary artery obstruction.

It is enrolling patients in nine centers in Europe, Asia, and North America who are 18 and older with suspected CAD but no known history of CAD. The participants also have normal renal function and are not taking any medications that lower heart rate.

The study population is "a cohort of patients previously not considered candidates for CCTA with standard reconstruction." Andreini said. They hypothesized that intracycle motion compensation would be "a powerful tool to reduce false positives and improve the diagnostic accuracy in patients with higher baseline heart rates."

The 71 patients in this initial analysis had a mean age of 66, and 59% were male. They had a mean body-mass index (BMI) of 27 and an average heart rate of 71 beats per minute.

Compared with conventional CCTA, adding the motion-correction algorithm increased the percentage of images that were interpretable from 77% to 86% and the percentage of coronary arteries that were free from motion artifacts from 71% to 86%—both significant improvements.

The percentage of CT images from the left main coronary artery that were interpretable was similar without and with motion correction (94% vs 97%). However, the interpretable images from the left anterior descending artery improved from 72% to 94%. The increase in interpretable images was greatest for the right coronary artery (which is most affected by motion); this increased from 46% to 70%.

There was also a significant improvement in image quality and freedom from motion artifacts—per coronary segment and per coronary artery.

Andreini is on the speaker's bureau of GE Healthcare. Truong has no disclosures.

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