Detection of Coronary Artery Stenosis by Low-Dose, Prospectively Electrocardiogram-Triggered, High-Pitch Spiral Coronary Computed Tomography Angiography

Study Questions:

What is the diagnostic accuracy of a newly developed protocol for coronary computed tomographic angiography (CTA) utilizing prospective electrocardiogram (ECG)-triggered, high-pitch low tube current?


CTA using the ECG-triggered, high-pitch methodology was attempted in 75 patients with suspected coronary artery disease (CAD). Twenty-five patients were excluded for body weight >100 kg or failure to lower heart rate to ≤60 bpm, leaving 50 patients who underwent CTA and conventional coronary arteriography.


CTA was successful in all 50 patients, 16 of whom had CAD on standard arteriography. Single-vessel CAD was noted in seven patients, and two- and three-vessel disease in four patients each. One patient had left main stenosis. Analyzed on a per-patient basis, CTA had a sensitivity of 100% (16/16), specificity of 82% (28/34), a positive predictive value of 72%, and a negative predictive value of 100%. On a per-vessel basis, sensitivity and specificity were 100% and 94%, with all 29 stenotic vessels accurately identified and the absence of disease correctly identified in 161 of 171 vessels. On a per-vessel basis, positive and negative predictive values were 74% and 100%. Analyzed on a per-segment basis, 46 of 50 diseased segments were correctly identified with a sensitivity of 92%, and 670 of 686 disease-free segments accurately characterized for a specificity of 98%. The mean estimated effective radiation dose was 0.76 ± 0.08 mSv (0.64-0.95 mSv). An additional average radiation exposure of 0.21 ± 0.05 mSv was attributable to the test acquisition.


In patients who were ideal candidates for CTA, ECG-triggered, high-pitch spiral coronary CTA is highly accurate for detection of coronary stenosis, with an estimated radiation exposure <1.0 mSv.


Coronary CTA has clearly been demonstrated to be an accurate means of detection and exclusion of CAD, with negative predictive values of 100% being common in fairly large trials. The limitation of early algorithms for CTA was substantial radiation exposure as high as 12-30 mSv in earlier studies. This exceeds the exposure for invasive coronary arteriography, which averages 5-7 mSv. Multiple algorithms have been utilized to reduce the radiation exposure including ECG gating, modulating tube current during nonimaging periods, high-speed spiral dual-detector methodology, and using lower tube voltage. In this study, a high-pitch spiral acquisition was utilized, which reduces the number of overlapping images and hence the total exposure. These techniques allowed capture of the entire coronary tree during a single diastole with a significant reduction in estimated radiation exposure compared to many other protocols without a loss of accuracy. It should be emphasized that this was a fairly limited study with only 50 patients from the original cohort; one-third were excluded as being a nonideal candidate based on strict heart rate criteria or body weight >100 kg. As the major advantage of CTA is its exceptionally high negative predictive value (95-100% in virtually all studies), it may be an ideal tool for utilization in low-risk individuals, many of whom are likely to be either women or younger age, where there is legitimate clinical concern regarding radiation exposure. Reduction of the radiation exposure to the ≤1.0 mSv range, as demonstrated here, should go a long way toward alleviating many of these concerns.

Clinical Topics: Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Atherosclerotic Disease (CAD/PAD), Interventions and Coronary Artery Disease, Interventions and Imaging, Computed Tomography, Nuclear Imaging

Keywords: Coronary Artery Disease, Coronary Stenosis, Electrocardiography, Diastole, Tomography, Spiral Computed, Heart Rate

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