Novel approaches for the treatment of chronic total coronary occlusions

Despite major advancements in the technology used for the percutaneous treatment of coronary artery disease, chronic total occlusions (CTOs) persist as a major challenge to the interventional cardiologist with relatively low success rates. CTOs are evident in 20% of patients undergoing cardiac catheterization and are responsible for the majority of cases that are referred to bypass surgery. There is growing evidence that patients may benefit from recanalization of a CTO by alleviation of angina, improving left ventricular function, and potentially long-term survival. The major obstacle to percutaneous recanalization of CTOs is the inability to cross the occlusion with coronary guidewires. Even when crossed, the operator has to deal with the exact location of the distal wire (e.g., dissection or true lumen) and the existence of relatively long lesion requiring multiple stents with high restenosis rates. New technologies for CTO revascularization have been focused mainly on a mechanical approach including specialized guidewires and more recently, specific devices using highly sophisticated technology such as laser guidewire, optical coherence reflectometry, and a blunt microdissection catheter. An alternate biological approach involves the local administration of enzymes such as plasminogen activators (urokinase) or collagenase, which can act locally to specifically degrade the collagen content of the CTO, thereby "softening" the occlusion and allowing easier guidewire crossing. In conclusion, CTOs emerge as a great technical challenge and are the focus of novel series of mechanical and biological approaches.