Survival Advantage for Bypass Surgery Compared With Coronary Angioplasty In coronary heart disease (CHD), plaque builds up inside the coronary arteries that supply oxygen-rich blood to the heart muscle. The plaque is made up of cells, fibrous tissue, fatty substances such as cholesterol, and possibly calcium deposits. Over time, the plaque can limit or block the flow of blood to the heart muscle, resulting in chest pain, heart attack, heart failure, or erratic heart beats. Each year, more than a million procedures are performed to open or bypass blocked coronary arteries to improve blood flow to the heart muscle. In a new comparative effectiveness study of more than 189,000 older adults, researchers found that patients with stable CHD who underwent coronary artery bypass grafting (CABG) had better long-term survival rates than those who underwent percutaneous coronary intervention (PCI) to improve blood flow to the heart muscle. Background Comparative effectiveness research looks at the advantages and disadvantages of various approaches to a specific health issue for particular patient groups. Results provide information to help patients and health care providers decide which practices are most likely to offer the best approach for a particular patient, what the timing of interventions should be, and the best setting for providing care. This study compared two common treatments for CHD, CABG and PCI (with or without stenting). CABG, also known as bypass surgery,is the most common type of heart surgery in the United States. During CABG, a healthy artery or vein from the body is connected, or grafted, to the blocked coronary artery. The grafted artery or vein bypasses (that is, goes around) the blocked portion of the coronary artery, creating a new path for oxygen-rich blood to flow to the heart muscle. Surgeons can bypass multiple coronary arteries during one surgery. PCI, also known as coronary angioplasty, is a less invasive, nonsurgical procedure used to open narrowed or blocked coronary arteries. During the procedure, a thin, flexible catheter (tube) with a balloon at its tip is threaded through a blood vessel to the affected artery. Once in place, the balloon is inflated to compress the plaque against the artery wall. This restores blood flow through the artery. A stent (small mesh tube) is usually placed in the artery to help keep it open. What was the study? “Comparative effectiveness of revascularization strategies” was published in the New England Journal of Medicine online March 27 and in the April 19, 2012, print edition. This observational study examined the comparative effectiveness of CABG and PCI. - The American College of Cardiology Foundation (ACCF) and the Society of Thoracic Surgeons (STS) developed a partnership, the ACCF and STS Database Collaboration on the Comparative Effectiveness of Revascularization Strategies (ASCERT), to compare the outcomes of PCI and CABG.
- This unique study linked clinical databases containing information on patient procedures with administrative databases to track long-term outcomes. Records were analyzed on:
- 86,244 patients from the STS Adult Cardiac Surgery Database who underwent CABG.
- 103,549 patients from the ACCF National Cardiovascular Data Registry who underwent PCI (78 percent received drug-eluting stents, 16 percent received bare-metal stents, and 6 percent did not receive a stent).
- Followup claims data of the same patients from 644 U.S. hospitals from the Medicare Provider Analysis and Review database of the Centers for Medicare and Medicaid Services (CMS).
- All patients analyzed from the registries were 65 years of age or older and had stable CHD that involved two or three vessels. The patients had not had a heart attack within the previous 12 months.
- All patients underwent PCI or CABG between 2004 and 2007. The CMS claims data were from 2004 to 2008. The followup time ranged from 1 to 5 years, with an average of 2.72 years.
- The primary endpoint was all-cause survival. The researchers compared CABG and PCI in the overall population and in several subgroups.
- Because this was an observational study, the patients were not randomized to receive either PCI or CABG treatment. State-of-the-art statistical methods were used to make the two patient populations as similar as possible. The differences between the groups included:
- Patients undergoing PCI were on average older, a larger percentage were female, and the patients more often had two-vessel disease, compared with those undergoing CABG.
- More patients undergoing CABG had heart failure, diabetes, high blood pressure (hypertension), chronic lung disease, cerebrovascular disease, a history of smoking, or peripheral arterial disease, compared with patients undergoing PCI. These patients more often had three-vessel disease.
What did the study find? Overall, older adults with stable CHD who underwent CABG had better long-term survival rates than those who underwent PCI to improve blood flow to their heart muscle. These real-world data from more than 180,000 patients at 644 hospitals nationwide indicate that the favorable survival rates for CABG extend across the entire United States and across a variety of patient subgroups. - At 1 year, there were no differences in survival rates between the two groups (6.2 percent vs. 6.6 percent death rate for CABG and PCI, respectively).
- At 4 years, patients who had bypass surgery had a 21 percent lower mortality than those who underwent PCI (16.4 percent vs. 20.8 percent death rate for CABG and PCI, respectively).
- The long-term survival advantage after CABG was the same for all patient subgroups, regardless of age, sex, body mass index, or the presence of diabetes, chronic lung disease, or having had a previous heart attack. The sheer scale of the data (189,000 patients) allowed for an unprecedented analysis of subgroups.
- There are limitations in this type of study:
- There is selection bias in the patients, as illustrated by the different baseline characteristics between the two groups. The investigators used statistical methods to address this bias.
- Nevertheless, some variables that were not measured in the patients could influence the results. For example, if a large number of patients underwent PCI because they were considered too frail to undergo CABG, this could account for part of the difference in mortality between the two groups.
- Because the study was limited to Medicare patients aged 65 and older, the findings may not extend to younger patients.
What are the take-home messages? This study provides information to help physicians and patients determine the best approach to treat CHD. - Doctors should discuss the various options with their patients, including both short- and long-term pros and cons. The best treatment for each patient may vary according to their individual circumstances. For some patients PCI will be a more suitable option, and for others CABG will be preferable.
- Observational studies such as this one complement results from randomized controlled trials (RCTs). They provide insights on real-world outcomes that are more broadly representative than results from RCTs, which typically study more defined populations.
Where can I learn more? Health Information - Health Topics: Cardiac MRI, Cardiac Rehabilitation, Coronary Angioplasty, Heart Attack, Heart Failure, Heart Surgery, How the Heart Works, Clinical Trials
- Understanding Clinical Trials: Frequently Asked Questions
Research - Weintraub, W.S., Grau-Sepulveda, M.V., Weiss, J.M., … & Edwards, F.H. (2012). Comparative effectiveness of revascularization strategies. New England Journal of Medicine, 366(16), 1467-1476.
- Mauri, L. (2012). Why we still need randomized trials to compare effectiveness. New England Journal of Medicine, 366(16), 1538-1540.
- Implications of the ASCERT comparative effectiveness study (NHLBI Director’s Corner)
- NIH study shows survival advantage for bypass surgery compared with non-surgical procedure (news release)
Related Research Spotlight Study Summaries Additional study information - The ASCERT study was supported through designated comparative effectiveness research funds from the American Recovery and Reinvestment Act.
- ASCERT involved 16 investigators from among the five collaborating organizations: Christiana Care Center for Outcomes Research in Newark, DE; the ACCF in Washington, DC; the STS in Chicago, IL; Duke Clinical Research Institute in Durham, NC; and PERFUSE Angiographic Core Laboratories & Data Coordinating Center, a nonprofit academic research organization in Boston, MA.
June 2012 |
