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Chronic total occlusions (CTOs) are identified in about a fifth of patients with coronary artery disease (CAD) undergoing nonemergent catheterization. Even though the vast majority are symptomatic, only about one-third of CTOs receive revascularization, with surgery about twice as common as percutaneous intervention, according to a Canadian registry study published in the March 13, 2012, issue of the Journal of the American College of Cardiology.

Bradley H. Strauss, MD, PhD, of Sunnybrook Health Sciences Centre (Toronto, Canada), and colleagues reviewed the records of 14,439 patients who underwent diagnostic angiography at 3 centers participating in the Canadian Multicenter CTO Registry from April 2008 through July 2009. The investigators analyzed the clinical and angiographic characteristics as well as the management strategy of 1,697 CAD patients in whom at least 1 CTO was identified.

CTO prevalence was 14.7% overall and 18.4% among those with significant CAD.

LV Function Normal for Most

Although CTO patients tended to be older and sicker than the general cath lab population, only 40% had prior MI and 12% had a history of heart failure. Nearly half presented with ACS, and only 13% reported no or mild symptoms (Canadian Cardiovascular Society class 0/1). LV function was normal (grade 1) in more than half of patients, while only 17% had significantly reduced LV function (grade 3/4).

In terms of anatomic distribution, most solitary CTOs were located in the right coronary artery (47%), while the remaining third were in the LAD (20%) and left circumflex (16%) arteries. In 78% of cases, the lesions appeared in the proximal or mid portion of the vessel. Moreover, 17% of patients had a CTO in more than 1 artery.

In addition, 76% of CTO patients had multivessel disease, and 7% exhibited significant stenosis of the left main trunk. Significant Q waves corresponding to the CTO territory—indicating absence of myocardial viability—were found for only 32% of RCA, 13% of LAD, and 26% of left circumflex lesions.

Less Than Half Treated Invasively

Overall, 44% of patients were managed medically without revascularization, while 26% underwent CABG and 30% received PCI. However, the CTO artery was grafted in only 88% of the surgical group, and PCI specifically of the CTO lesion was attempted in only 10% of patients, with a 70% success rate.

In terms of clinical characteristics, medically treated patients tended to be somewhat older than those who underwent revascularization and were more likely to have high-risk characteristics such as renal insufficiency, prior MI, and prior PCI. Compared with medically treated patients, those referred for PCI were younger and less likely to have diabetes, renal insufficiency, prior MI, and complex coronary anatomy.

Management strategy varied among the 3 participating centers in regard to medical therapy (P < 0.001) and CTO PCI (ranging from 16% to 1%; P < 0.001). No difference, however, was observed in use of CABG.

According to the authors, the discrepancy between the CTO revascularization rates and the incidence of normal or near-normal LV function “suggests that a substantial proportion of CTO patients with indirect evidence of myocardial viability are not undergoing some form of revascularization. To clarify this issue, future studies should include objective assessment of viability in the CTO territory.”

For Jeffrey W. Moses, MD, of Columbia University Medical Center/Weill Cornell Medical Center (New York, NY), the most concerning finding was the 53% prevalence of 3-vessel disease in the medically treated group. “In multivessel CTO patients, you should be even more compelled [to intervene] because at least 1 of those lesions is subtending 2 territories,” he noted.

“This highlights the problem that no scrutiny is being given to the underutilization of revascularization in areas where the consensus is that it prolongs life and certainly improves quality of life,” he told TCTMD in a telephone interview.

Revascularization the Issue—Not PCI vs. CABG

Most of these CTOs need revascularization, Dr. Moses insisted. “I don’t care how you do it,” he commented. “If PCI is not going to be successful, then send [the patient] to CABG. If they have left main disease plus a CTO—especially if it’s in a right [coronary artery]—you can make a good argument that those people should have bypass.

“But it’s the nonintervention group that confuses me,” he continued. “There’s a lot of disease there that’s just being treated medically. It’s really hard to understand what the logic is.”

Dr. Moses offered several possible reasons why physicians were making what he viewed as inappropriate therapeutic choices. One is poor understanding of CTO physiology. “Very few CTOs, even if they are single lesions, get adequate [perfusion] to prevent ischemia. By definition, CTOs are ischemic, and collaterals are almost never adequate [to overcome that deficit],” he said, suggesting that another factor may be that some operators are simply not technically adept enough to attempt such difficult procedures.

But a third, broader explanation, Dr. Moses said, is that many clinicians do not understand the place of coronary revascularization in contemporary practice. “There’s total confusion in the field,” he said, noting that underutilization “needs to be scrutinized.”

“This is a very disturbing study,” Dr. Moses emphasized. “The main message is that PCI treatment of CTOs—at least in Canada—is infrequent, despite all the advances that have been made.” Although there are some cultural and center-related variations in practice, CTO summits have been taking place around the world for years without much impact, he observed.

Study Details

Chronic total occlusion was defined as 100% luminal diameter stenosis without a discernible lumen and the absence of antegrade flow, known or assumed to be of at least 6 weeks’ duration, on the basis of prior angiography or presence of a concordant ACS.

Source:

Fefer P, Knudtson ML, Cheema AN, et al. Current perspectives on coronary chronic total occlusions: The Canadian Multicenter Chronic Total Occlusion Registry. J Am Coll Cardiol. 2012;59:991-997.

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