 The dual-source CT DSCT equipped with two X-ray tubes at 90 degree offset in the gantry can provide temporal resolution 83ms using mono-segmental reconstruction technique. The recent studies about the effect of heart rate on IQ of DSCT coronary angiography which concluded in adequate diagnostic IQ of dual-source CTCA without immediate pre-scanning heart rate control included chronic users of β-blocker focused on the influences of average heart rate, heart rate variability and coronary arterial calcifications on IQ. The effect of blooming artifact of calcification on IQ by far cannot be eliminated. Here, we investigate the effects of maximum heart rate, average heart rate, minimum heart rate and heart rate variability on the motion-related IQ of DSCT coronary angiography in patients without both pre-scanning heart rate control and chronic use of β-blocker agent, compared with that in chronic users of β-blocker agents. 