SAN DIEGO – Bilateral internal thoracic artery grafting is a reasonable revascularization strategy in suitable patients up to 70 years of age, results from a large Canadian study showed.
Although observational studies have suggested that bilateral internal thoracic artery grafting (BITA) can be ideal for this population of patients, it is used in just 4% of coronary artery bypass graft (CABG) cases in North America and 12% of CABG cases in Europe, Dr. Teresa M. Kieser said at the annual meeting of the Society of Thoracic Surgeons.
Dr. Teresa M. Kieser
"Why is it not used more often?" asked Dr. Kieser, a cardiac surgeon at the University of Calgary (Alta.). "Longer OR times, technical demands, and risks to patients. BITA today is reserved for the young, but who are the young? Currently there are no age guidelines for the performance of CABG with BITA. We set out to determine if there is an age cutoff point until which BITA is better."
She and her associates studied 5,601 consecutive patients who underwent isolated primary CABG between April 1995 and March 2008 and were followed to March 2009. The patients were linked to the Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease (APPROACH), an ongoing initiative that captures detailed clinical information on all patients undergoing cardiac catheterization and subsequent intervention in the province of Alberta since 1995.
The researchers used a Cox model to compare survival by type of internal thoracic artery graft used (bilateral, single, or none), and they adjusted for baseline clinical and demographic differences. The primary outcome was all-cause mortality, which included operative mortality. Secondary outcomes included cardiac catheterization, percutaneous coronary intervention, repeat CABG, and death within 1 year.
The mean age of the 5,601 patients was 64 years; 18.5% underwent BITA, 72% had single internal thoracic artery grafting (SITA), and 9.5% underwent CABG with vein only.
Dr. Kieser reported that, compared with patients in the other treatment groups, those in the BITA group were younger and more often male; had less comorbidity, lower European System for Cardiac Operative Risk Evaluation scores, and a higher ejection fraction; and underwent cardiac catheterization more often for stable angina.
The proportion of repeat procedures within 1 year of CABG was similar among all groups. However, those who underwent BITA had significantly lower mortality at 1 year, compared with their counterparts in the SITA and vein-only groups (2.4% vs. 4.3% and 8.2%, respectively).
During a mean follow-up of 7 years, 1,233 patients (22%) died. Patients in the BITA group had significantly lower crude long-term mortality, compared with those in the SITA and vein-only groups (16.7% vs. 40.1% and 42%, respectively). "This survival difference appeared to increase over prolonged follow-up," Dr. Kieser said.
After multivariable adjustment, the survival advantage for patients in the BITA groups was no longer statistically significant. "Perhaps a longer period of follow-up will clarify the presence or absence of a BITA advantage," she said.
A spline analysis that plotted hazard ratio for BITA relative to SITA across ages showed a trend toward a survival benefit of BITA, compared with SITA, in patients up to the age of 70 years. Age therefore appeared to be a modifier of the BITA effect.
"As the benefits of BITA become more obvious over time, a longer period of follow-up will be needed to confirm or deny the advantage of a BITA strategy," Dr. Kieser said. "We must advise caution in use of BITA in patients older than 70 years until more is known about BITA in this age group."
Dr. Kieser said that she had no relevant financial conflicts to disclose.