Background: Coronary computed tomographic angiography (CCTA) has been demonstrated to improve efficiency in the evaluation of patients with acute chest pain. However, these studies were conducted in controlled environments and real world impact of such strategy has not been confirmed. Method: In this single centre observational study, we used a novel CCTA orientated chest pain pathway for intermediate risk chest. The pathway is executed by exclusively by routine hospital staff. Comparisons were made with historical records 12 months prior. Primary endpoint was the length of stay and rate of same-day discharge. Secondary endpoint included rate of invasive angiography, proportion of significant angiographic findings and chest pain representations within 3 months for those whom coronary disease has been ruled out. Safety end points included coronary events and cardiovascular death. Results: From 1/10/2012 to 30/9/2014, 385 patients (60% of eligible patients) were assessed using the pathway. Length of stay was 2.3days (historical data 1.7 days) for overall and1.0 days (1.6 days) with coronary ischaemia ruled out. Same-day discharge rate was 33.9% (14.6%) and 40.4% (17.2%). Chest pain presentation within 3 months after ruling out was 3% (9%) and no coronary events (2 coronary events in the historical arm) occurred within 3 months. Rate of significant findings on coronary angiography is 64% (46%). Conclusion: The CCTA focussed pathway has demonstrated improvement in all primary and secondary endpoints in a real world setting. The main drawback was the lower than expected rate of compliance in using the pathway.

Background: Intermediate (50-70%) stenoses on CTCA frequently prompt further investigation. Noting that contrast intensity tends to decrease more markedly across more severe lesions, we aimed to develop a simple technique to quantify this intensity reduction, and evaluate its efficacy in assessing the severity of coronary stenoses. Methods and Results: Data from 33 consecutive patients with an intermediate stenosis on CTCA and subsequent invasive coronary angiography (ICA) in St Vincent's Hospital, Sydney were analysed. Exclusion criteria included significant motion artefacts, excessive calcification or coronary stents involving the target lesion. The investigators were blinded to the ICA results. The difference of the minimum Hounsfield unit (HU) count measured across each stenosis and a reference segment immediately proximal to the lesion were used to determine the absolute and percentage reductions in HU. 39 intermediate stenoses among 33 CTCAs were assessed and compared to ICA: 18 stenoses were graded >70% by ICA. Using an absolute cut-off of 123 HU reduction, the sensitivity, specificity, positive predictive value and negative predictive value for > 70% ICA stenosis were 100%, 76.2%, 78.3% and 100%, respectively; and for a percentage HU reduction cut-off of 30%, the corresponding results were 100%, 71.4%, 75.0% and 100%, respectively. Conclusion: Measurement of the HU reduction across intermediate coronary lesions on CTCA provides useful discrimination of the less severe stenoses at subsequent ICA. Our results suggest that the strong negative predictive value of an absolute reduction <123 HU or a relative reduction <30% would obviate the need for further investigation.