CT coronary angiography in low- to intermediate-risk patients: less radiation, less invasive angiography, and less revascularisation.

Objectives: We investigated whether any change in the use of invasive coronary angiography and coronary revascularisation after CT coronary angiography in patients with a low to intermediate pre-test probability of coronary artery disease could be explained from alterations in patient characteristics.

Design: A cohort study based on data samples from the Western Denmark Heart Registry. Follow-up ended on 11 March 2014.

Results: A total of 3541 persons were examined during the period of January 2010-December 2013. The median radiation dose was reduced from 4.2 to 2.2 mSv (p < 0.001) due to improved technology. The immediate referral rate for subsequent myocardial perfusion scans was increased from 2.8% to 10.0% (p < 0.001), while the immediate referral rate for invasive coronary angiography decreased from 25.3% to 10.8% (p < 0.001). The revascularisation rate diminished from 10.4% to 6.3%. The multivariable adjusted hazard ratio (95% confidence interval) for invasive coronary angiography during follow-up after CT coronary angiography was 0.59 (0.47-0.74) and that for coronary revascularisation was 0.66 (0.45-0.97) in 2013 compared to that in 2010.

Conclusions: The radiation dose diminished considerably. The reductions in the use of invasive coronary angiography and coronary revascularisation could not be explained by changes in patient characteristics but are driven by an increased use of perfusion scans in combination with increasing use of measurement of functional coronary flow reserve.