OBJECTIVE: To determine the effects of heart rate frequency (HRF) and heart rate variability (HRV) on radiation exposure and image quality in a large cohort of patients undergoing DSCT (dual-source computed tomograph) coronary angiography with three different electrocardiogram (ECG) pulsing models, to prospectively investigate CT image quality parameters by using different protocols and to calculate the radiation dose estimates for noninvasive coronary angiography performed by DSCT. METHODS: Over a 1-month period, 253 consecutive patients were recruited and categorized into 3 groups: Group A:low HRF (</= 75 beats/min) with normal-minor heart rate variability (HRV) (mean interbeat difference (IBD), 0 - 3), coronary CT angiography proceeding with prospective ECG-triggered flash spiral scan; Group B: intermediate-high HRF (> 75 beats/min) with normal-minor HRV (IBD, 0 - 4), with prospective ECG-triggered sequence scan; Group C: intermediate-high HRF (> 75 beats/min) with moderate-severe HRV (IBD >/= 5) with retrospective ECG-gated spiral scan. RESULTS: CT coronary angiography yielded excellent image quality in 87.7% of patients (222/253). No significant differences were found among three groups with different HRF and HRV in image quality and diagnostic performance. Radiation exposure was significantly higher in patients with low versus high HRF and in patients with severe versus normal HRV. Significant difference (P < 0.001) was found among the effective doses of group A (mean +/- standard deviation, 0.602 +/- 0.363 mSv), group B (1.253 +/- 0.804 mSv) and group C (9.039 +/- 5.657 mSv). CONCLUSION: The higher temporal resolution of dual-source spiral CT coronary angiography performed with adaptive ECG pulsing results in preserved diagnostic image quality and performance independent of HRF or HRV at the cost of limited dose reduction in arrhythmic patients.