Conduit Choice and Volume-Outcome Relationships in Multi-Arterial Coronary Artery Bypass Grafting in Medicare Beneficiaries in the United States

D. Tam¹, q. chen¹, A. Sallam², S. Fremes³, M. F.L.. Gaudino⁴, M. E. Bowdish⁵, J. Chikwe^6
1Cedars Sinai Medical Center, Los Angeles, California ²Department of Cardiac Surgery, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California ³Sunnybrook Health Science Center, Toronto, Ontario ⁴Weill Cornell Medicine, New York, New York ⁵Cedars Sinai Medical Center, La Canada, California ⁶Cedars-Sinai, Los Angeles, California

Purpose: Multi-arterial revascularization is under-utilized despite guideline recommendations for coronary bypass (CABG) conduit choice. This study was designed to evaluate the role of surgeon experience on use and outcomes of multi-arterial revascularization.

Methods: Using US Centers for Medicare and Medicaid data, we identified 9,516 patients undergoing isolated, primary, non-emergency multi-arterial revascularization including 2,430 (26%) who received radial artery and 7,086 (74%) who received bilateral internal thoracic artery (BITA). Individual surgeons were grouped into tertiles based on conduit use: low volume surgeons performed < 3 radial arteries or 2 BITAs per year, and high-volume surgeons performed >10 or 4 respectively. The primary outcome was all cause mortality. The secondary outcome of major adverse events (MACE) was a composite of death, myocardial infarction, or repeat revascularization compared in a multivariable Cox-proportional hazard model adjusting for 27 pre-operative variables in addition to the individual surgeon’s case volume of each conduit. Patients undergoing multi-arterial grafting were also compared to patients undergoing single arterial grafting(n=18,375), stratified by multi-arterial and overall CABG volume respectively.

Results: The median patient age was 72 (IQR: 68-72) and multi-arterial revascularization was used in 34%: those receiving radial artery were younger ( 71.9 vs. 72.6 years) and more likely diabetic (50.9% vs 45.5%) compared to BITA recipients. Adjusted 30-day death was similar (2.0% vs 1.3%, adjusted OR: 0.71, 95%CI: 0.47-1.04, p=0.091). There was no difference in 30-day mortality by surgeon volume tertile in the radial group (1.0%, 1.2%, and 1.7%, p=0.427), however 30-day mortality was 1.4%, 1.8%, and 3.2% (p < 0.001) for high, medium, and low volume BITA users. There was no difference in 4-year mortality between patients receiving radial (87.3%) versus BITA (85.0%) (adjusted HR: 0.85, 95%CI: 0.70-1.02, p=0.087) but freedom from MACE was higher in the radial group (85.2% versus 81.4%) (HR: 0.84, 95%CI: 0.71-0.98, p=0.03). Surgeon experience was not associated with significant differences in long-term outcomes in patients receiving radial artery, but late mortality (Figure A, HR 1.32, 95%CI: 1.08-1.61, p=0.0048) and MACE (Figure B, HR: 1.23, 95%CI: 1.04-1.45, p=0.014) were worst among infrequent users of BITA compared to higher volume surgeons. Compared to single-arterial revascularization, reductions in MACE were associated with multi-arterial revascularization only when used by medium/high volume surgeons (HR: 1.28, 95%CI; 1.09-1.49, p< 0.001).

Conclusion: Using radial artery as the second conduit in multi-arterial revascularization was associated with improved event-free survival in patients >65-years, compared to BITA. The benefits of multi-arterial grafting appear negated when surgeons perform fewer than two such operations per year.

Identify the source of the funding for this research project: None