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Advantages to Coronary Artery Bypass Surgery Come to Light: Surgery, but not stenting, protects patients with stable coronary disease from future heart attacks and death.

When coronary artery disease (CAD) has narrowed an artery by 70%, the risk of heart attack becomes a concern, and it's time to discuss revascularization.

Until recently, the optimal choice of revascularization procedure was relatively straightforward: If you had one or two lesions threatening to cause a heart attack, angioplasty and stenting (percutaenous coronary intervention, or PCI) would be recommended. If severe atherosclerosis was present throughout your left anterior descending (LAD) artery, as well as other arteries in your heart, coronary artery bypass grafting (CABG) would be advised.

But now that millions of patients have undergone these procedures, other factors have come to light. Leading cardiologists recently presented evidence that PCI and

CABG do not have the same long-term impact.

"CABG provides what we call a 'field protection effect.' Not only does it prevent the culprit lesion from causing a heart attack, but it also protects against future heart attacks caused by lesions that may develop in the same artery," Cleveland Clinic heart surgeon Faisal Bakaeen, MD, explains. "To this end, CABG improves long-term survival.

"Stents do a good job of treating individual lesions, but they cannot protect against a future lesion. As such, they cannot protect against future heart attacks or improve survival," he explains.

When Revascularization May Be Necessary

CAD is a disease caused by atherosclerosis. Fatty plaques accumulate inside artery walls. These plaques can cause a vessel to become so narrow that blood can no longer pass through it. Plaques also can rupture, spilling their contents into the artery and causing a clot that stops blood flow. Either way, the result is a heart attack.

When a heart attack occurs, the area of heart muscle that is nourished by the affected artery is starved of oxygen and can die. Revascularization with PCI or CABG reestablishes adequate flow of freshly oxygenated blood to these areas.

What We Have Learned

The benefits of revascularization are directly related to the extent of the disease (disease burden). When someone has significant CAD throughout their coronary arteries, CABG can extend their life.

"Even if the disease hasn't progressed far enough to worry about an imminent heart attack, improving blood flow to the heart muscle will protect against a future heart attack," says Dr. Bakaeen.

The greater the disease burden, the more significant the benefit from CABG. Take diabetes, for example. Diabetes accelerates the development of CAD, increasing the risk of an early heart attack.

"In these patients, CABG has demonstrated clear superiority over PCI in terms of survival and preventing future heart attack," says Dr. Bakaeen.

How CABG Prolongs Life

Most heart-attack-causing lesions occur in the upper one-third of an artery. CABG bypasses these lesions and much of the remaining artery by attaching the bypass graft far downstream in an area less vulnerable to disease. As the disease continues to evolve in the artery, the bypass graft continues delivering oxygenated blood to the heart muscle nourished by the artery. This is how CABG prevents future heart attacks from occurring.

PCI cannot do this. "PCI only addresses a single lesion. It cannot protect an artery that develops a new lesion upstream or downstream from the stent," says Dr. Bakaeen.

"Moreover, the stent itself can become narrowed or clot," Dr. Bakaeen adds. "When this happens, blood flow stops. Because there is no alternative route for blood to follow, the heart muscle can die."

Where PCI Shines

PCI offers different advantages. PCI focuses on treating acute lesions that limit or stop blood flow. This makes it ideal when a single blockage is causing a heart attack.

"You stent it, allow the patient to recover and then discuss what to do next to prevent another heart attack," says Dr. Bakaeen.

There are times when a patient's overall condition makes PCI a safer choice, as well--for example, when a patient has a comorbidity such as severe lung disease, liver disease or extreme age. In such cases, the risks associated with surgery may be greater than the risk of heart attack.

In general, however, the new thinking is to look beyond the immediate effect of treatment to its long-term impact.

"If the goal is preventing future heart attacks, CABG is the answer," says Dr. Bakaeen.

RELATED ARTICLE: All CABGs Are Not Created Equal.

For patients to benefit from CABG, bypass grafts must stay open a long time. This is best accomplished by using arteries as grafts to important coronary vessels. Arteries are less vulnerable than veins to plaque formation.

The gold standard CABG graft is the left internal mammary artery (LIMA) to the LAD, the heart's most important artery. In appropriate patients with multivessel disease, Cleveland Clinic surgeons also use the right internal mammary artery and an artery from the arm as bypass grafts to other important arteries.

"The benefit of using these additional arterial grafts Is not as profound as with the LIMA to LAD, but they add protection against future heart attack while improving quality of life," says Dr. Bakaeen. "Our own research suggests that using these additional arterial grafts instead of veins translates into survival benefit starting five to seven years later."

The ongoing ROMA trial is designed to confirm this finding, but results won't be published for five to 10 years. "In the interim, we tailor the CABG operation to each patient to ensure the best possible results," says Dr. Bakaeen.

Caption: This illustration shows a left internal mammary artery (LIMA) bypass graft (in white) to the left anterior descending artery (LAD). The graft reroutes blood around an obstruction in the LAD, bringing blood to heart muscle nourished by this important artery. New research shows that bypass grafts not only prevent an obstruction from causing a heart attack, but also can prevent damage from blockages that may occur later in the same artery. Stents can open a target lesion, but cannot protect against future events.
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Publication:Heart Advisor
Date:Sep 1, 2019
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