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Chronic total occlusions—a stiff challenge requiring a major breakthrough: is there light at the end of the tunnel?
  1. S Aziz,
  2. D R Ramsdale
  1. The Cardiothoracic Centre, Liverpool, UK
  1. Correspondence to:
    Dr David R Ramsdale
    The Cardiothoracic Centre Liverpool, Thomas Drive, Liverpool. L14 3PE, UK;

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Chronic total occlusion (CTO) remains one of the more difficult challenges for coronary interventionists. Innovations are essential if old, calcified, and long CTOs are to be successfully recanalised without acute complication and with a satisfactory short and long term outcome. Recent developments have included devices for breaking through the fibrous cap by blunt microdissection, an ultrasound device for “softening” resistant CTOs, and a device for differentiating between plaque and normal vessel wall to aid safe passage of a guidewire to the lumen beyond. This paper will review current practice and recent technological advances that are aimed at overcoming problematic CTOs.


Although it is often impossible to know exactly when the occlusion occurred, a CTO is arbitrarily defined as a > 3 month old, total obstruction of a coronary artery. A definition of > 1 month is likely to result in higher reported success rates for a particular treatment strategy.


CTOs consist of various degrees of fibro-atheromatous plaque and thrombus depending on the mechanism of occlusion and its duration (fig 1). A tough fibrous cap is often present at the proximal and distal margins of the CTO, with softer material in between. Endothelialised microchannels that traverse the occlusion increase the likelihood of passage with low profile hydrophilic guidewires. When the fibrous occlusion is long, densely organised and homogenous, and when microchannels are absent, guidewire passage is less successful and subintimal dissection likely.

Figure 1

 Microscopic section through a chronic total occlusion (CTO) with visible tiny microchannels. Courtesy of Dr John Gosney, Royal Liverpool University Hospital, Liverpool.

The clinical and technical problem

Approximately 30% of all coronary angiograms in patients with coronary artery disease will show a CTO and its presence often excludes patients from treatment by percutaneous coronary intervention (PCI).1 CTOs are one of the commonest reasons for referral for coronary artery bypass surgery (CABG) and many …

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