Coronary Chronic Total Occlusions: Revascularization in the Right Cases Improves Clinical Results

Coronary chronic total occlusion (CTO), defined as TIMI 0 flow for more than three months, is seen on nearly one-third of routine coronary angiograms. Despite the prevailing opinion that CTO is benign, experts in CTO management disagree.

“It’s traditionally taught that if a lesion is closed, it can’t get worse,” says Cleveland Clinic interventional cardiologist Jaikirshan Khatri, MD. “But physiologically, CTO is associated with significant ischemic burden. When used judiciously in conjunction with non-CTO percutaneous coronary intervention (PCI), bypass surgery and optimal medical therapy, PCI for CTO can improve outcomes for patients with coronary artery disease.”

That’s a key message of an update on coronary CTO management that Dr. Khatri recently published with two Cleveland Clinic colleagues in a December 2017 supplement to Cleveland Clinic Journal of Medicine.

How clinical results improve

The new paper outlines several of the clinical benefits of CTO PCI:

• In patents with CTO-related angina that’s refractory to medical therapy, PCI can produce symptom relief similar to that obtained by coronary artery bypass grafting (CABG) at one month.
• Studies have shown that successful CTO PCI can also have a positive impact on mortality risk. “Meta-analyses of observational data in symptomatic and ischemic patients who underwent CTO PCI show reduced rates of all-cause mortality, major adverse cardiac events and need for subsequent CABG,” Dr. Khatri notes.
• Opening coronary CTOs has been shown to have beneficial effects on left ventricular systolic function in patients with viable myocardium in the corresponding coronary territory. The improvement in systolic function appears to be sustained at three years.

The issue? Incomplete revascularization

In patients with patent but stenotic coronary arteries, it is known that physiologically driven decisions to revascularize can produce superior clinical results, Dr. Khatri observes.

“There is an ischemic burden threshold beyond which revascularization is superior to optimal medical therapy,” he explains. “In this setting, we know that CTO is associated with ischemic burden. Patients with symptoms related to CTO represent a subset of patients with incomplete revascularization. In this way, CTOs are similar to borderline lesions. But while we treat borderline lesions, we have traditionally tended to not treat CTOs.”

Angiography insufficient

Anatomic considerations alone are insufficient in determining whether to proceed with PCI, Dr. Khatri says.

“We know from traditional angiography that eyeballing an estimate isn’t helpful in borderline blockages,” he notes. “We need to obtain a measurement of the blockage to direct our decision.” This is where fractional flow reserve (FFR) is useful for informing the risk-benefit analysis of PCI versus medical treatment, he adds. “The lower an FFR value is below 0.8, the greater the benefit of PCI. The higher the value above 0.8, the greater the benefit of medical therapy. All CTOs have a value less than 0.8 independent of the size and quality of collaterals supplying the distal vessel.”

Noninvasive assessment of ischemic burden can also be conducted with myocardial perfusion imaging, he points out. In CTO, ischemia greater than 12.5 percent is predictive of significant improvement in symptoms after intervention.

Dr. Khatri and colleagues provide a helpful algorithm for determining the need for and method of coronary revascularization in patients with CTO in the following figure from their recent Cleveland Clinic Journal of Medicine review.

Image content: This image is available to view online.

View image online (https://assets.clevelandclinic.org/transform/f4ec43db-0ff8-4563-9ae0-98693b80ea21/Khatri-inset650x450_jpg)

Figure. An algorithmic approach to determining the need for and method of coronary revascularization in patients with coronary CTO. Reprinted, with permission, from Khatri et al., Cleveland Clinic Journal of Medicine (2017;84[suppl 3]:27-38).

A steep and long learning curve

The difficulty of performing CTO PCI has discouraged many operators from attempting it. As a result, Dr. Khatri and colleagues note in their review, the volume of CTO PCIs is less than 5 percent of total PCIs performed in the U.S. — and success rates remain low, at 59 percent.

But the combination of operator experience, improved technology and widespread adoption of a hybrid algorithm for the procedure published by Brilakis and colleagues in 2012 has improved results. High-volume centers now report procedural success rates as high as 92.9 percent.

“There is a strong correlation between a center’s CTO PCI volume and CTO PCI success rates,” says Dr. Khatri. “CTO PCI success remains heavily dependent on operator expertise, as a steep and long learning curve is involved.”

The unique technical aspects of CTO PCI, such as retrograde and subintimal guidewire tracking, have accelerated procedural success but can be associated with higher rates of adverse cardiac events compared with traditional antegrade and intraluminal guidewire tracking. “This makes it a difficult procedure that should be reserved for experienced operators,” Dr. Khatri says.

Improving on a good thing

At Cleveland Clinic, where several cardiologists collectively perform more than 100 CTO PCIs per year, the overall safety of the procedure is enhanced by use of bilateral radial artery access.

“The Achilles’ heel of PCI is a 1-in-1,000 chance of a life-threatening bleed with femoral access,” Dr. Khatri notes. “But the risk of a life-threatening bleed is substantially reduced when operators go through the wrist.”

He and his colleagues are researching several techniques to simplify, shorten and improve CTO PCI. “We hope to get the technique and technology good enough that it becomes a routine procedure with high safety and success rates,” he explains.

Image at top reprinted, with permission, from Khatri et al., Cleveland Clinic Journal of Medicine (2017;84[suppl 3]:27-38).