Computed tomography as a tool for percutaneous coronary intervention of chronic total occlusions

Chronic total occlusions (CTO) constitute a major challenge in percutaneous coronary revascularisation (PCI). The development of new interventional strategies, the availability of purpose made tools including dedicated catheters and wires, as well as increasing expertise by the operators, have contributed to the modest success rates which today hover around 75%. Case selection is of utmost importance since failure of this high risk procedure with its typically high radiation doses, high contrast doses and increased complication rates is associated with long term adverse events. Imaging of the coronary arteries using the gold standard of invasive coronary angiography allows characterisation of the chronic total occlusion and is often able to predict the probability of successful recanalisation. Multislice computed tomography (MSCT) is increasingly being utilised as a non-invasive diagnostic imaging modality to detect coronary artery disease. Its ability to provide information on the soft tissue (including plaque) surrounding the lumen has been applied to better define the morphological features of CTOs. In fact, the amount of calcification, tortuousity and actual length of the occluded segment which are established predictors of success, are all better characterised by MSCT. Three dimensional reconstruction of the coronary anatomy and its integration with two dimensional fluoroscopy images during the actual CTO-PCI procedure may help to identify the best angiographic projection, offering a directional guide at the angiographically "missing segment". More technological advances are needed to optimise this multi-modality imaging integration. Whether this will result in better success rates for CTO-PCI is still the subject of ongoing research. It is then that we can evaluate the true benefit of the use of MSCT for CTO against the risk from excessive radiation associated with this strategy.