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High-Pitch Thoracic CT With Simultaneous Assessment of Coronary Arteries: Effect of Heart Rate and Heart Rate Variability on Image Quality and Diagnostic Accuracy
Study Questions:
Using a high-pitch spiral image acquisition protocol for computed tomography angiography (CTA) and a dual-source system, what mean heart rate and heart rate variability (HRV) are required for diagnostic imaging of the coronary arteries simultaneously with thoracic CT for noncardiac purposes?
Methods:
High-pitch thoracic CT was performed in 111 consecutive patients (mean age 60.2 ± 11.5 years; range 37-81 years) using a dual-source system (2 x 128 0.6 mm sections, 38.4 mm collimation width, 0.28-second rotation time). Data acquisition was prospectively electrocardiographically triggered at 60% of the R-R interval using a pitch of 3.2. Image quality was evaluated using a 3-point scale (1 = excellent, 2 = moderate, 3 = poor).
Results:
Close interobserver agreement was found for image quality scores of 1,998 evaluated coronary segments (κ = 0.93). Image quality was of diagnostic value in 828 of 1,739 segments (47.6%). In 29 of 111 patients (26%), diagnostic image quality was observed for all segments. Average heart rate and HRV were significantly higher in patients with at least one nondiagnostic coronary segment compared with those without (p < 0.001). All patients with mean heart rates <64 bpm and HRV <13 bpm had diagnostic image quality in all coronary segments. Effective radiation dose for thoracic CTA was 1.9 ± 0.66 mSv. The mean scan time was 0.9 ± 0.1 second.
Conclusions:
Simultaneous evaluation of coronary arteries in high-pitch dual-source CTA of the thorax for noncardiac purposes is consistently diagnostic in patients with low heart rates and HRV, whereas most patients not receiving beta-blockers had at least one segment that was not diagnostic because of higher heart rate and HRV. Beta-blockers are recommended if there are no contraindications and coronary interpretation is anticipated.
Perspective:
This study demonstrates that CTA requires a relatively low heart rate and low HRV; and that if heart rate and HRV both are low, then anatomic data about the coronary arteries can be obtained on thoracic spiral CT scans performed for noncardiac purposes. Neither the actual use of beta-blockers nor the accuracy of CTA relative to an external standard was tested.
Keywords: Tomography, X-Ray Computed, Risk Factors, Electrocardiography, Observer Variation, Heart Rate, Tomography, Spiral Computed, Radiation Dosage, Heart Diseases, Coronary Angiography, Coronary Vessels, Bradycardia
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