High-pitch thoracic CT with simultaneous assessment of coronary arteries: effect of heart rate and heart rate variability on image quality and diagnostic accuracy.

OBJECTIVES

The aim of this study was to evaluate the mean heart rate and heart rate variability (HRV) required for diagnostic imaging of the coronary arteries simultaneously with thoracic computed tomography for noncardiac purposes, applying a high-pitch spiral image acquisition protocol for computed tomography angiography (CTA) using a dual-source system.

BACKGROUND

For the primary prevention of coronary heart disease, screening methods to identify currently asymptomatic people who are at high risk for developing coronary heart disease are essential. Coronary CTA can rule out coronary artery stenoses with high negative predictive value.

METHODS

High-pitch thoracic computed tomography was performed in 111 consecutive patients (mean age 60.2 ± 11.5 years; range 37 to 81 years) using a dual-source system (2 × 128 0.6-mm sections, 38.4-mm collimation width, 0.28-s 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 for image quality scores of 1,998 evaluated coronary segments was found (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 (p<0.001) higher in patients with at least 1 nondiagnostic coronary segment compared with those without. All patients with mean heart rates <64 beats/min and HRV <13 beats/min 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 s.

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 1 segment that was not diagnostic because of heart rate and HRV. Beta blockers are recommended if there are no contraindications and coronary interpretation is anticipated.