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Background CT coronary angiography (CTCA) is an established non-invasive imaging modality for assessing coronary artery disease (CAD). Advances in scanner technology, particularly the transition from 64-slice scanners that require a minimum of 3 heart beats for complete coverage of the heart, to 16 cm detector, single heartbeat CT scanners, offer potential improvements in diagnostic accuracy, radiation dose reduction, and minimization of unnecessary invasive procedures. We sought to evaluate the clinical impact of a single heartbeat 640-slice CTCA on diagnostic performance and invasive management.Methods A retrospective, observational study was conducted at the Golden Jubilee National Hospital a tertiary cardiology centre providing cardiovascular imaging for the west of Scotland. Patients were identified from routine cardiac CT scanning lists before and after the installation of 16cm detector, single heartbeat scanner in July 2020. From May 2019 to February 2020 500 patients were scanned using a 64-slice scanner (GE LightSpeed CT750 HD) and from November 2020 to July 2021 500 patient were scanned on a 640-slice scanner (Canon Aquilion One). The outcomes of interest were rates of subsequent invasive coronary angiography (ICA), need for repeat CTCA, radiation dose (dose-length product, DLP), and rates of revascularization (percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG)).Results Patient characteristics and scan parameters are summarised in table 1. Total radiation dose was significantly lower (DLP: 235.49 vs. 285.60, p=0.0015) and fewer patient required repeat CTCA scan on the day of imaging (7 vs. 39 patients, p=0.048) The use of the 640-slice CT scanner significantly reduced the need for subsequent ICA (16% vs. 25.2%, p<0.05). Revascularization by PCI was numerically higher in the 640-slice group (64 vs. 47 patients, p = ns), CABG rates were similar (20 vs 22 patients). Pressure wire use was numerically lower in patients undergoing angiography following CTCA on a single heartbeat scanner.Abstract 6-009 Table 1Comparison of patient characteristics, heart rate and radiation dose. BMI – body mass index, bpm – beats per minute, DLP – dose length product 64 slice scanner 640 slice scanner Male gender – no.(%) 221 (44) 212 (42) Age – yr (mean ± SD) 57.9 ± 11.5 58.4 ± 10.7 Weight – kg (mean ± SD) 85.1 ± 21.5 87.1 ± 21.7 BMI – kg/m2 (mean ± SD) 29.2 ± 6.3 31.9 ± 10.0 Heart rate – bpm (mean ± SD) 60.4 ± 11.1 59.0 ± 10.7 Intravenous beta blocker -no.(%) 369 (73.8) 356 (71.2) Radiation dose (DLP) – mGy.cm (median(IQR)) 204 (227) 199 (129) Repeat CTCA – no.(%) 39 (7.8) 7 (1.4) Conclusion In this observational study a single heartbeat, 640-slice CT scanner reduced the need for repeat scanning, reduced radiation dose and led to fewer diagnostic invasive coronary angiograms. These findings support the prioritization of single heartbeat CT technology for CAD assessment in clinical practice.Abstract 6-009 Figure 1Invasive angiography, pressure wire use, intravascular imaging and revascularization following CT imaging