The term chronic total coronary occlusion (CTO) describes an occluded coronary artery of at least three months duration with absolutely no angiographically detectable flow through the lesion itself (TIMI 0 flow)1. An important characteristic of a CTO is the length of the actually occluded segment which can only be assessed by way of simultaneous visualisation of the proximal segment and the distal segment through collateral filling. Other important features to be assessed from the diagnostic angiography are the tortuosity of the occluded segment and the degree of calcification, which are determinants of treatment success2,3.
The basic pathoanatomic features of a CTO consist of a proximal cap of the occlusion, which is often fibrotic or calcified and may provide considerable resistance to advancement of the wire; then, along the occlusion length follows a segment of loose fibrous tissue or organised thrombus with various degrees of adventitial and intraluminal neovascularisation, and various extents of calcification4,5. If this segment is very long, as most often occurs within the right coronary artery, multislice computed tomography (MSCT) might be helpful in defining the general direction of the vessel course. Finally, the distal cap needs to be passed towards the segment distal to the occlusion: this is often tapered and constricted and provides a small target for the distal wire entry.
The fact that a CTO requires specific techniques was recognised early by the pioneers of CTO recanalisation, such as Geoffrey Hartzler and Bernhard Meier, but it is only in the past decade that interventional techniques have developed considerably with new wire technologies and wire handling, advanced primarily by Japanese colleagues2,6. A further boost to achieving success rates of recanalisation above 90% came from the development of the retrograde approach. However, the primary strategy in the majority of cases remains the antegrade technique.