The study is the largest in the United States to examine the safety and effectiveness of a so-called retrograde approach to angioplasty and stenting of chronic total occlusions (CTOs). Using this innovative technique, interventional cardiologists at three medical centers were successful in tunneling through the obstruction, opening the blocked artery and restoring blood flow to the heart in about 80 percent of patients, many of whom had no alternative treatment options.
“Patients with chronic total occlusions experience chest pain, shortness of breath and other disabling symptoms,” said Tesfaldet T. Michael, MD, a cardiology research fellow at the University of Texas Southwestern Medical Center inDallas. “When medical therapy fails, percutaneous coronary intervention (PCI) may be the last resort. It really helps patients to have a better quality of life.”
Up to one-third of patients who undergo diagnostic angiography have cholesterol plaque that completely blocks a coronary artery. If they have previously had coronary artery bypass surgery, a surgeon may be reluctant to operate again. Still, only about 10 percent of CTOs are treated with PCI, largely because of the difficulty of getting an angioplasty balloon and stent across the hardened plug from the front end, and the lower success rates when compared to conventional PCI, which involves an artery that is narrowed but not blocked.
“PCI of CTOs is fundamentally different,” said Emmanouil Brilakis, MD, PhD, FSCAI, director of the cardiac catheterization laboratory at the Veterans Affairs (VA) North Texas Healthcare System in Dallas. “We can do non-CTOs with a success rate of nearly 100 percent. PCI of CTOs has about a 50 to 70 percent success rate using the antegrade (front-end) approach, even in experienced centers. It is very resource intensive and markedly less successful.”
The retrograde, or back-end, approach to CTOs may be more successful because the cholesterol plug tends to be softer, more tapered, and easier to cross at its far end. There are several variations of the retrograde technique. In each case, the back-end catheter and wire are moved into position by following a path of alternative arteries known as collaterals or by being threaded through an existing bypass graft, if the patient has previously had coronary artery bypass surgery.
In the simplest version of retrograde PCI, called the true-to-true technique, a back-end wire is pushed directly through the blockage to the front end. Today, a more common approach is called reverse CART (controlled antegrade and retrograde tracking and dissection). Using this technique, catheters with wires inside are threaded to both the front and back end of the occlusion. The interventional cardiologist then uses the front-end wire to tunnel into the artery wall just below the surface. Inflation of a tiny balloon enlarges the space and breaks through the tissue layer into the inside of the artery where the blockage is. The back-end wire is then advanced into the space created by the balloon. Once the back-end wire has crossed the blockage, inflation of another balloon opens the artery and pushes aside the cholesterol plaque. Stenting may then be done via the front or back end of the plaque, depending on the specifics of each case.
A third option, called CART, switches the roles of the front- and back-end wires, with the back-end wire used to accomplish the initial tunneling into the artery wall.
For the study, researchers analyzed data from 401 consecutive patients treated with retrograde CTO interventions at threeU.S.hospitals. The procedures were performed at St Joseph’s Hospital in Bellingham, WA (led by William Lombardi, MD, FSCAI); Piedmont Heart Institute in Atlanta (led by Dimitri Karmpaliotis, MD); and the VA North Texas Healthcare System in Dallas (led by Dr. Brilakis). Half the patients in this study had previously had bypass surgery. In 52 percent of cases, the retrograde approach was used after a standard antegrade approach had failed.
The retrograde CTO intervention was successful in 79.3 percent of patients. The true-to-true puncture was used in 47 percent of cases, reverse CART in 41 percent, and CART in 12 percent. Sixteen patients (4 percent) experienced major procedural complications, including death in one, heart attack in two, tearing of a bypass graft in two, puncture of an artery in 10, and difficulty removing PCI equipment in one.
“There is a lot of interest among interventionalists to train in CTO interventions,” Dr. Brilakis said. “The retrograde technique has a very steep learning curve, but we need many more trained operators in theUnited States, given the number of patients and the complexity of the procedures. We hope this report stimulates more people to do this.”
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