FT. LAUDERDALE, FLA. – Coronary artery bypass graft surgery shows a clear long-term survival advantage in certain high-risk groups over percutaneous coronary intervention, based on results of the largest study of real-world data so far.
The survival advantage for a composite high-risk group – including patients aged 75 years and older, patients with diabetes, those with ejection fractions (EF) less than 50%, and those with a glomerular filtration rate (GFR) less than 60 mL/min per 1.73 m2 – was 28% at 4 years, Dr. Fred H. Edwards reported at the annual meeting of the Society of Thoracic Surgeons.
The findings come from the ASCERT (The American College of Cardiology Foundation – The Society of Thoracic Surgeons Collaboration on the Comparative Effectiveness of Revascularization Strategies) study, in which researchers compared catheter- and surgery-based procedures using the existing ACC and STS databases, as well as the Centers for Medicare and Medicaid Services 100% denominator file data. The study was designed to identify specific patient characteristics that favor one mode of treatment over the other.
The ACC and the STS both have large registries containing detailed clinical information on millions of procedures. However, the information in these databases extends to only 1 month after the procedure. The researchers linked this short-term clinical information with the administrative data registry from the CMS to provide long-term mortality, rehospitalization, and resource utilization outcomes. The 3- to 5-year outcomes after coronary artery bypass graft (CABG) surgery are being compared with those after percutaneous coronary intervention (PCI) – primarily using drug-eluting coronary stents, from the STS and ACC databases, respectively. In addition to survival, researchers are assessing the need for additional procedures and hospitalizations, new cardiac disease conditions, and the medications being taken at various points in time after the coronary artery procedure.
Patients in this CMS population were at least 65 years of age with two- to three-vessel disease. Patients with either single-vessel disease or left-main disease were excluded.
"[This study has] a population that is actually 10 times greater than the sum total of all patients ever having been enrolled in randomized [revascularization] trials," said Dr. Edwards, who is medical director of cardiothoracic surgery at the University of Florida/Shands Jacksonville,and chairman of the STS National Database.
Data from both the STS and ACC databases were linked to data from the CMS. A propensity score – the probability of having CABG – was calculated for each patient, and clinically important subgroups were identified before the files were linked. The propensity scores and inverse weighting were used to calculate adjusted survival curves. "Then we compared the survival for coronary bypass and percutaneous intervention for groups having very similar characteristics," said Dr. Edwards.
High- and Low-Risk Groups Identified
This analysis included a total of 189,793 patients, of which 103,549 received PCI. Dr. Edwards presented the survival results for high-risk subgroups; the overall results will be presented at the ACC’s Annual Scientific Session in March, he said.
High-risk subgroups include patients who were aged 75 years and older, had diabetes, had EFs less than 50%, and had a GFR less than 60 mL/min per 1.73 m2.
For those aged 75 years and older, the mortality risk ratio at 4 years was 0.78 favoring surgery. Correspondingly, the survival advantage in this group for surgery was 22%. For patients with three-vessel disease, the survival advantage at 4 years was 25%. Patients with insulin-dependent diabetes had a 28% survival advantage at 4 years with CABG, compared with PCI. For patients with EFs less than 50%, the survival advantage with surgery was 30% at 4 years.
However, there appears to be a survival advantage with PCI in these groups at up to 1 year of follow-up. "We should keep in mind that in many of these subgroups, the survival with percutaneous intervention is better than surgery in that first 6-10 months after the procedure. The reason for that, of course, is the procedural mortality," Dr. Edwards said.
They also defined a low-risk population (about 20% of the total population). They looked at survival advantages at years 1-4. "I think this is important because it illustrates that surgery really does start to declare its advantage in year 1 to year 2. Then it looks like it begins to plateau off a little bit," he said. "Still, at 4 years for both high-risk and low-risk patients, you’ve got more than a 25% survival advantage for surgery."
He noted that "this is a Medicare population, so we would be on shaky ground if we tried to extrapolate these results to a global population."