Chronic Total Occlusions
A Chronic Total Occlusion (CTO) is defined as an artery that has been completely occluded for greater than 30 days. Chronically occluded coronary arteries account for approximately 20-30% of the documented coronary disease encountered in coronary catheterization labs today. Currently there are three methods for treatment of CTO's: percutaneous intervention, coronary artery bypass surgery (CABG) and medical management. Less than 10% of CTO cases are managed by percutaneous intervention. Approximately 40% of the CTOs are managed by surgical means and 50% by medications alone.
Medical therapy (e.g., nitrates, calcium, and beta blockers) is partially efficacious, but rarely completely eliminates either the symptoms or the objective evidence of the ischemia. Coronary Bypass Surgery is effective so long as the distal target vessel is anatomically suitable for insertion of a bypass graft. The limitations of the bypass surgery are well known and include significant patient morbidity, risk of surgical mortality, and significant expense.
The third option is percutaneous intervention. This minimally invasive, less costly procedure accounts for approximately 10% of coronary intervention cases. Percutaneous intervention is accomplished by using conventional guidewire techniques to slowly 'poke' and 'prod' through the occlusion. This procedure is successful 30-90% of the time depending on the operator skill and case selection criteria. The time spent to recanalize a chronic total occlusion is estimated to be between 5 minutes and several hours with an average time of about 30 minutes.
This standard procedure can often be associated with dissection and perforation of the vessel as the guidewire is extensively manipulated within the vasculature. It is estimated that dissection occurs in 15% of the cases as the guidewire is often navigated through a 'false' lumen. Perforation occurs in approximately 1-2% of the cases.
Successful recanalization typically results in improvement of clinical symptoms, normalization of a positive exercise test, and significant reduction in the need for bypass surgery.
