Anyone who has coronary artery disease (CAD) needs to have aggressive medical therapy and risk factor modification, both to reduce the risk of heart attack, and to control symptoms of angina (if present).
Sometimes medical therapy alone is insufficient, and revascularization therapy is needed. Revascularization means that areas of significant obstruction in the coronary arteries are relieved with either angioplasty and a stent, or with bypass surgery (also called coronary artery bypass grafting, or CABG).
So, in any person diagnosed with CAD, the doctor and patient should consider two questions. First, is medical therapy alone sufficient, or should revascularization also be done? Second, if revascularization is recommended, should it be with stenting, or with CABG?
In most people who have CAD, medical therapy, along with appropriate lifestyle changes to improve cardiac risk, should be the approach of choice. Specifically, in people who have stable angina (angina that is predictable in onset, and that occurs only under specific circumstances such as exercise), medical therapy is as effective as revascularization in preventing heart attacks and reducing the risk of cardiovascular death. So medical therapy in such cases is virtually always the treatment of choice.
However, revascularization therapy is usually the better choice under some circumstances. These include:
• People who have the type of heart attack known as acute ST-Segment elevation myocardial infarction (STEMI).
• People with either unstable angina or non-ST-segment myocardial infarction (NSTEMI), who do not become stable quickly with aggressive medical therapy.
• People who have stable angina that is insufficiently controlled despite maximal medical therapy, or who cannot tolerate the medical treatment necessary to control it.
• People whose CAD anatomy puts them in a category where revascularization is more likely than medical therapy to improve survival. These include people who have significant blockage in their left main coronary artery, and those who have significant blockages in all three major coronary arteries — the right, left anterior descending and left circumflex arteries. Read more about coronary artery anatomy.
Once it is decided that revascularization is required, the next decision is whether to use angioplasty and stenting, or CABG.
Stenting is generally preferred over CABG in patients with STEMI, since it is the quicker way to open the blocked coronary artery. Stenting is also usually preferred in people with the other forms of acute coronary syndromes (ACS, such as NSTEMI or unstable angina), when rapidly opening the blocked coronary artery is deemed to be necessary.
In people with stable angina who have failed with medical therapy, stenting is generally preferred for those who have CAD involving a single coronary artery.
In those with stable angina who need revascularization and have two-vessel CAD, stenting is also generally recommended unless they also have diabetes, or their coronary artery anatomy is considered to be complex.
CABG is believed to yield better long-term outcomes in people with 3-vessel CAD.
CABG is thought to also give better results than stenting in most people with disease of the left main coronary artery. However, in those who have ACS due to blockage in the left main artery, stenting may be the safer choice since it can be done much more quickly.
CABG is a better option than stenting in people with 2-vessel CAD who also have diabetes.
Finally, in general, people revascularized with CABG less frequently need repeat revascularization than those who receive stents. For this reason, CABG should be at least discussed as an option with almost anyone who needs revascularization.
If we were going to summarize the situations in which CABG is preferred over stenting, we would say that the outcomes tend to be better with CABG in people who have “complex” CAD. “Complex” CAD includes people with 3-vessel disease, left main CAD, some people with 2-vessel disease, and almost anyone with diabetes who has CAD.
The SYNTAX trial, published in 2009, is the most definitive randomized clinical trial to compare stents to CABG in patients with complex CAD. This study showed that patients treated with CABG had significantly fewer endpoint events (a composite of death, stroke, heart attack, and the need for repeat revascularization) than patients receiving stents (12.4% vs 17.8% after 12 months). Similar results were reported in the BEST trial in 2015.
So the two major randomized clinical trials comparing stents to CABG in patients with complex CAD both came out in favor of CABG.
Cardiologists point out, however, that in the SYNTAX trial, while the composite endpoint was worse with stents, the short-term risk of stroke appears higher after CABG (0.6% for stents vs. 2.2% for CABG) after 12 months. This is a legitimate point, though the risk of stroke was statistically equivalent in both groups after three years.
Investigators who ran the SYNTAX trial have since developed what they call a “SYNTAX score,” which essentially grades the characteristics of a patient’s CAD in terms of its complexity. Patients with lower SYNTAX scores appear to do relatively better with stents than those with higher SYNTAX scores. However, while many cardiologists use the SYNTAX score to help decide whether a person with complex CAD should have stenting or CABG, this scoring system itself has not been tested in a clinical trial.
The bottom line is that for most people who need coronary artery revascularization, and who have severe triple-vessel CAD or significant blockage in their left main coronary artery, CABG usually should be considered the primary mode of therapy.
Stenting is generally preferred in people who have ACS, in people with single-vessel CAD, and in many people with 2-vessel CAD who do not have diabetes.
Using stents instead of CABG for complex CAD ought to be reserved for people who, after understanding all the risks and benefits, still opt for the less invasive approach.