Coronary Artery Chronic Total Occlusion

Coronary artery chronic total occlusion (CTO) is defined as an occluded coronary artery segment without anterograde flow for at least three months. It can be classified as a “true” or “functional” CTO based on flow characteristics. In “true” CTO, there is no anterograde flow. In “functional” CTO, there is minimal anterograde flow through the occluded segment of the coronary artery. CTO is a common finding during coronary angiography and its prevalence may vary depending on the reported literature. Among patients without previous coronary artery bypass grafting (CABG), CTO is found in about 20–30% of the patients. CTO may develop insidiously over a period of time and involve a complex interplay between intracellular and extracellular factors, smooth muscle and foam cells, calcification, and neovascularization. There is a growing body of evidence to support that CTO revascularization may improve clinical outcome when compared to medical management. Both the European and American cardiovascular societies support CTO revascularization with a class 2a recommendation (level of evidence B). Historically, due to low procedural success rate, apparent inefficient resource utilization, potential increase in complication rates and uncertain clinical benefits, only about 10–20% of patients with CTO are treated with percutaneous coronary intervention (PCI). Recent advances using novel and innovative techniques with dedicated equipment have significantly improved the procedural success rate for CTO PCI to about 90% in the hands of experienced operators. With increasing interest in CTO PCI coupled with increased educational effort, CTO PCI likely will become more accessible to patients in need of CTO revascularization. Ongoing advancement in innovative techniques and equipment will continue to improve procedural success rates and reduce procedural complication rate for CTO PCI. Furthermore, there are a number of prospective clinical trials on the horizon which should help define the clinical benefits and limitations of CTO PCI in the near future.