Open Coronary Artery Bypass Graft (CABG): A Fading Standard for Treatment of Coronary Artery Disease?

Treatment of acute coronary artery disease was first accomplished surgically via the coronary artery bypass graft procedure some 45 years ago, then by angioplasty 32 years ago and finally by stenting 23 years ago.  Despite the evolution of treatment alternatives (which continue to evolve), CABG has represented a benchmark, if not gold standard, against which alternative treatments are judged.  Below is an excerpt from the MedMarket Diligence report, "Worldwide Market for Drug-Eluting, Bare Metal and Other Coronary Stents, 2008-2017" (Report #C245).

Coronary artery bypass graft (CABG) surgery is one of the therapies that can be used to treat patients whose coronary arteries are excessively blocked. CABG patients are typically selected for the procedure depending on the extent of their disease and the severity of symptoms while taking into account the patient’s age and the presence of other medical conditions that might make a CABG procedure too risky.

The goal of CABG surgery is to relieve symptoms of coronary artery disease, including angina, to allow the patient to return to a normal lifestyle and to lower his or her risk of suffering a heart attack or other cardiac incident.

Roughly 1,313,000 inpatient PCI procedures were performed in 2006 while 448,000 inpatient bypass procedures were performed, according to the American Heart Association. More than 800,000 CABG procedures were performed worldwide annually.

An open CABG procedure uses a blood vessel graft to restore normal blood flow to the heart. Most often, three or four arteries are bypassed in a single surgery. Typically, the grafts are harvested from the patient’s own arteries and veins from the chest (thoracic), leg (saphenous) or arm (radial). Internal mammary arteries (IMAs, also known as internal thoracic arteries [ITAs]) are the most common types of grafts used because of the excellent long-term success rates associated with use of these arteries. Often, ITAs can remain intact at their origin and thus maintain their own oxygen-rich blood supply. The other end is sewn to the coronary artery below the site of the blockage. Upwards of 90% of all CABG patients receive at least one internal artery graft. Other thoracic arteries used in CABG include the gastroepiploic and the inferior epigastric arteries.

To perform an open CABG procedure, the patient is placed on a cardiopulmonary bypass (CPB or heart-lung bypass) machine that temporarily takes over the function of the heart and lungs during surgery, thus maintaining the circulation of the blood and the oxygen content of the body. This “on-pump” surgery allows the surgeon to perform the bypass on a still heart.

Unfortunately, complications associated with CPB machines can be significant. These can include: postperfusion syndrome, hemolysis, capillary leak syndrome, clotting of blood in the circuit (particularly in the oxygenator), stroke, air embolism, device leakage (the patient will lose blood perfusion of tissues if a line is disconnected), kidney problems, and problems with mental clarity and memory.

Also, the costs incurred for procedures using a CPB machine are typically very significant. As such, several alternative procedures have been developed that allow coronary artery bypass to be achieved without the use of a CPB or heart-lung machine.

With a traditional, open CABG, patients typically remain in the intensive care unit for one to two days after the surgery, then are transferred to a standard nursing unit for another three to five days. Generally speaking, an average hospital stay for conventional CABG patients is 6–10 days. Full recovery usually occurs within two or three months.

Some results still point to the superiority of CABG over DES in some patient groups, such as those with multivessel disease. For instance, results published online April 6, 2009 (ahead of print in Circulation) showed that in nearly 4,000 patients with multivessel coronary artery disease, the longer-term rates of myocardial infarction, death, and TVR after stenting was significantly higher with DES. The rates in this study, led by Shengshou Hu, Md, PhD of Fuwai Hospital (Beijing, China), were higher than those found in the DES arms of Syntax. For this study, 1,834 patients had DES while 1,886 had CABG between April 1,2004 and December 21, 2005. After three years of follow-up, the DES patients showed unadjusted TVR rate to be 17.6% versus 4.2% in CABG patients. However, because the study was nonrandomized, many physicians are reluctant to put much stock in the findings. Also, the DES used in the study were not commercial stents from the United States but instead were developed by Chinese companies. Both paclitaxel and sirolimus stents were used in the study. 

Techniques for the performance of CABG continue to evolve, spanning off-pump ("beating heart") bypass, minimally invasive options (e.g., minimally invasive direct coronary artery bypass graft or MIDCAB), and even percutaneous CABG.

See MedMarket Diligence Report #C245.

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