Novel techniques for assessment of functional significance of coronary artery stenoses by coronary angiography and cardiac computed tomography

It is widely accepted that revascularisation guided by functional assessment of coronary artery stenosis is superior to anatomical assessment by coronary angiography alone. Fractional flow reserve (FFR) is now the established ‘gold standard’ for functional assessment of coronary artery stenosis. However, routine invasive coronary angiography and fractional flow reserve evaluation for all patients with chest pain is not feasible or economically viable. Therefore, it would be ideal if there is a non-invasive modality that can provide both anatomical and functional assessment of coronary artery stenosis. In this thesis, the utility of cardiac computed tomography for not only anatomical but also functional assessment of coronary artery stenosis was assessed. We confirmed that CT coronary angiography (CTA) has excellent sensitivity and negative predictive value but lacks specificity and positive predictive value. Meanwhile novel adjunct CT methods such as transluminal attenuation gradient (TAG320) and adenosine stress CT perfusion (CTP) have modest accuracy for predicting significant FFR. More importantly, when TAG320 and CTP are combined with CTA, there is incremental predictive value for predicting significant FFR. Some recent studies have highlighted the poor correlation between diameter stenosis on invasive coronary angiography and FFR. With this in mind, we evaluated adjunct predictors that improved the diagnostic accuracy of invasive coronary angiography for significant FFR. We showed that diameter stenosis alone on invasive coronary angiography has poor diagnostic accuracy for functional assessment of coronary artery stenosis. However, when lesion length and area of myocardium subtended by coronary stenosis is added to diameter stenosis (DILEMMA score), there is improvement in diagnostic accuracy.