Dual-Source CT Not Affected by Heart Rate When Evaluating Coronary Artery Stenosis

A recent study was conducted to determine the effect of heart rate, heart rate variability, and calcification on the ability to evaluate coronary artery stenosis on dual-source CT.

The Study
100 patients who underwent dual-source CT on the day before scheduled invasive coronary angiography.

Methodology
Prior to CT scanning, patients received 2.5 mg of isosorbide dinitrate. Prior to contrast administration, an Agatston calcium score was obtained on an initial non-enhanced CT.

Contrast (80 mL) was given using automated injection and the test-bolus technique to optimize enhancement of the coronary arteries.

Prospective tube current modulation was used to reduce radiation dose.

A single-segment reconstruction algorithm was applied for data reconstruction using the data of one fourth rotation of both detectors for image reconstruction.

Coronary arteries were evaluated using thin-slab maximum intensity projection images, curved-planar reformations, and 3-dimensional volume rendered images.

Image quality was subjectively assessed, and significant stenosis was considered >=50% luminal narrowing.

During invasive coronary angiography, the degree of stenosis was evaluated using quantitative coronary analysis. A significant stenosis was considered >=50%.

Coronary segments were classified according to the American Heart Association 13 segment model.

Results
Mean heart rate was 64.9 +/- 13.2 bpm, and mean heart rate variability was 23.6 +/- 36.2 beats per CT examination. Mean Agatston calcium score was 786.5 +/- 965.9. Median calcium score was 370.

Diagnostic image quality was obtained in 90.2% of coronary artery segments. In 9.8% of segments that were of poor or non-diagnostic image quality, 8.1% was due to severe calcification and 1.6% was due to motion artifact.

The sensitivity, specificity, positive-predictive value, and negative-predictive value of coronary CT compared with invasive angiography was 91.1%, 92.0%, 75.4%, and 97.5% by coronary segment, respectively, and 100.0%, 81.5%, 93.6%, and 100% by patient, respectively.

Multivariate regression analysis demonstrated that heart rate variability and calcium score were the only variables that significantly impacted image quality (P =0.015 and P <0.001, respectively).

Image quality was not significantly impacted by heart rate (P =0.14).

In this study, linear regression analysis demonstrated that good or excellent image quality can be obtained for heart rates up to 95.2 bpm.

Although heart rate variability affected image quality, it did not affect the accuracy of lesion detection.

The number of non-diagnostic segments was significantly affected by calcification only as this was the only factor that significantly affected diagnostic accuracy (P =0.001).

Conclusions
Dual-source CT demonstrates good quality images independent of heart rate over a wide range of heart rates. Image quality was affected by heart rate variability and particularly coronary artery calcification.

Reviewer’s Comments
The authors have demonstrated that the improved temporal resolution of dual-source CT further advances our capability of non-invasively evaluating coronary artery stenosis.

Author: Vineet R. Jain, MD

Brodoefel H, Burgstahler C, et al. Dual-Source CT: Effect of Heart Rate, Heart Rate Variability, and Calcification on Image Quality and Diagnostic Accuracy. Radiology; 2008; 247 (May): 346-355