Younger patients may have more long-term benefits from bilateral internal thoracic artery (BITA) grafting than older subjects, researchers said, following a new post hoc analysis of the Arterial Revascularization Trial (ART).
The findings were published in the Jan. 5/12 issue of the Journal of the American College of Cardiology by Weill Cornell Medicine’s Mario Gaudino, MD, MSCE, and colleagues.
The association of age with the outcomes of BITAs versus single internal thoracic arteries (SITAs) for coronary bypass grafting is still undetermined, the researchers said. The original ART study did not fully investigate the interaction of treatment with age, only in a small subgroup of patients age 70 years or older in the intention-to-treat analysis.
Observational studies and meta-analyses have at least suggested that patients receiving BITAs instead of SITAs for coronary artery bypass grafting (CABG) have better long-term outcomes. Others – including Teresa Keiser, MD, and colleagues – go as far as suggesting that the beneficial effects of the BITA grafting strategy may be seen only in younger patients.
The researchers, therefore, set out to evaluate the association between age and BITA versus SITA outcomes in the ART trial – the only large randomized controlled trial to compare outcomes of these two treatment groups in patients undergoing CABG. The ART study randomized 3,102 patients to 1 of the 2 treatment arms, and at 10-year follow-up, survival data were available for 97.7% of the patients.
In the new analysis, age was analyzed both as a categorical variable by decade and as a continuous variable, the researchers said. The median follow-up time was 10 years.
All-cause mortality and a composite of major adverse events, including all-cause mortality, myocardial infarction or stroke, were used as the primary endpoints, while secondary endpoints included bleeding complications and sternal wound complications up to 6 months after surgery. Multivariable fractional polynomials analysis and log-rank tests were used.
The assessment included the “Royston and Sauerbrei” approach, with multivariable fractional polynomials (MFP) to model the treatment by age interaction on the primary and secondary outcomes, which the researchers said avoided disadvantages associated with dichotomizing the data.
Although age did not affect any of the explored outcomes in the overall comparison in the intention-to-treat analysis, the researchers found there was a significantly lower incidence of major adverse events for younger BITA patients when restricting the analysis to patients aged between 50 and 70 years.
Zeroing in on this age group was driven by both clinical rationale, the researchers said – because this age group is most commonly represented among CABG patients and is where the balance between use of SITA versus BITA is stronger – and statistical rationale, because of patient numbers.
In full, ART’s patient population included just 237 patients age 76 or older, Jennifer S. Lawton, MD, of the Johns Hopkins University, MD, added in an accompanying editorial. She agreed with the researchers that the significantly lower incidence of major adverse events in the two largest subgroups (the 3,010 patients aged 51 to 70 years) do suggest that younger patients may derive the greatest benefit with BITA grafting.
Gaudino and colleagues also highlight that the 10-year all-cause mortality and cardiac death rates after CABG increased with age despite the competing risk of mortality from other causes, “indicating that mortality due to cardiovascular events increases with older age and is especially high in the age >80 years subgroup.
“In contrast, no difference across age for the composite of nonfatal cardiac events, especially across the age 51 to 75 years subgroups, was found.”
The researchers concluded that BITA could improve long-term outcomes in younger patients but stressed that more randomized data are needed.
Future trials of arterial revascularization focused on younger patients should seek to identify other subgroups likely to gain greatest long-term benefit, they said.
Lawton warned, however, that when deciding to use BITA grafting, “surgeon bias due to age alone should not be a deterrent to its use”.
She added, “If life expectancy is more than 5 years, a patient is likely to gain the associated benefit of prolonged survival from BITA grafting.”
Gaudino M, Di Franco A, Flather M, et al. Association of Age With 10-Year Outcomes After Coronary Surgery in the Arterial Revascularization Trial. J Am Coll Cardiol 2021;77:18-26.
Lawton JS. Why Not Give All Patients the Opportunity to Have the Benefits of BITA Grafting? J Am Coll Cardiol 2021;77:27-8.
Image Credit: Stanisław Remuszko / https://commons.wikimedia.org/wiki/File:Coronary_artery_bypass_surgery_2.jpg (Note: Use of this image does not constitute endorsement by the image author.)