Long-term Outcomes of Multiple Arterial Coronary Artery Bypass Grafting: A Population-Based Study of Patients in British Columbia, Canada

Abstract

Importance: Although the long-term survival advantage of multiple arterial grafting (MAG) vs the standard use of left internal thoracic artery (LITA) supplemented by saphenous vein grafts (LITA+SVG) has been demonstrated in several observational studies, to our knowledge its safety and other long-term clinical benefits in a large, population-based cohort are unknown.

Objective: To compare the safety and long-term outcomes of MAG vs LITA+SVG among overall and selected subgroups of patients.

Design, setting, and participants: In this population-based observational study, we included 20 076 adult patients with triple-vessel or left-main disease who underwent primary isolated coronary artery bypass grafting (MAG, n = 5580; LITA+SVG, n = 14 496) in the province of British Columbia, Canada, from January 2000 to December 2014, with follow-up to December 2015. We performed propensity-score analyses by weighting and matching and multivariable Cox regression to minimize treatment selection bias.

Exposures: Multiple arterial grafting or LITA+SVG.

Main outcomes and measures: Mortality, repeated revascularization, myocardial infarction, heart failure, and stroke.

Results: Of 5580 participants who underwent MAG, 586 (11%) were women and the mean (SD) age was 60 (8.7) years. Of 14 496 participants who underwent LITA+SVG, 2803 (19%) were women and the mean (SD) age was 68 (8.9) years. The median (interquartile range) follow-up time was 9.1 (5.1-12.6) years and 8.1 (4.5-11.7) years for the groups receiving MAG and LITA+SVG, respectively. Compared with LITA+SVG, MAG was associated with reduced mortality rates (hazard ratio [HR], 0.79; 95% CI, 0.72-0.87) and repeated revascularization rates (HR, 0.74; 95% CI, 0.66-0.84) in 15-year follow-up and reduced incidences of myocardial infarction (HR, 0.63; 95% CI, 0.47-0.85) and heart failure (HR, 0.79; 95% CI, 0.64-0.98) in 7-year follow-up. The long-term benefits were coherent by all 3 statistical methods and persisted among patient subgroups with diabetes, obesity, moderately impaired ejection fraction, chronic obstructive pulmonary disease, peripheral vascular disease, or renal disease. Multiple arterial grafting was not associated with increased morbidity or mortality rates at 30 days overall or within patient subgroups.

Conclusions and relevance: Compared with LITA+SVG, MAG is associated with reduced mortality, repeated revascularization, myocardial infarction, and heart failure among patients with multivessel disease who are undergoing coronary artery bypass grafting without increased mortality or other adverse events at 30 days. The long-term benefits consistently observed across multiple outcomes and subgroups support the consideration of MAG for a broader spectrum of patients who are undergoing coronary artery bypass grafting in routine practice.

Figure 1.. Adjusted Hazard Ratios and Cumulative Incidences of Long-term Outcomes for Multiple Arterial Grafting (MAG) vs Left Internal Thoracic Artery Supplemented by Saphenous Vein Grafts (LITA+SVG)

A-C, The adjusted cumulative incidences for mortality and repeated revascularization were estimated by incorporating weights that were obtained from propensity score (PS) weighting for the overall study cohort (LITA+SVG, n = 14496; MAG, n = 5580) at the end of 15-year follow-up. The adjusted cumulative incidences for myocardial infarction, stroke, heart failure, and the composite end point were estimated by incorporating weights that were obtained from PS weighting for the Discharge Abstract Database (DAD)-linked study cohort (LITA+SVG, n = 7912; MAG, n = 2633) at the end of 7-year follow-up. Cumulative incidences of mortality and the composite end point were estimated by the Kaplan-Meier method. For nonfatal long-term outcomes, cumulative incidences were estimated by the cumulative incidence function accounting for death as a competing risk. Adjusted hazard ratios were estimated from univariable Cox regression models that incorporated weights that were obtained from PS weighting. P values were calculated using the weighted Wald χ² test. B and C, The number of patients at risk was calculated by incorporating weights that were obtained from PS weighting (ie, weight of 1 for patients in the group receiving MAG and a weight equal to the odds of receiving MAG for patients in the group receiving LITA+SVG) and rounded to the nearest integer for the group receiving LITA+SVG.

Figure 2.. Adjusted Hazard Ratios of Long-term Mortality for Multiple Arterial Grafting (MAG) vs Left Internal Thoracic Artery Supplemented by Saphenous Vein Grafts (LITA+SVG) in Subgroups

Adjusted hazard ratios were estimated from univariable Cox regression models that incorporated weights that were obtained from propensity score (PS) weighting for each subgroup of the overall study cohort. P values were calculated based on the Wald χ² test for an interaction term included in a multivariable Cox regression model using the overall study cohort, adjusting for significant baseline covariates with a P value of <.1 that was retained in backward elimination. BMI indicates body mass index (calculated as weight in kilograms divided by height in meters squared); COPD, chronic obstructive pulmonary disease; EF, ejection fraction; PVD, peripheral vascular disease; Renal disease, dialysis, acute, or chronic renal failure, or estimated glomerular filtration rate of less than 60 L/min/1.73 m².

Figure 3.. Adjusted Hazard Ratios of Long-term Repeated Revascularization for Multiple Arterial Grafting (MAG) vs Left Internal Thoracic Artery Supplemented by Saphenous Vein Grafts (LITA+SVG) in Subgroups

Adjusted hazard ratios were estimated from univariable Cox regression models that incorporated weights that were obtained from propensity score (PS) weighting for each subgroup of the overall study cohort. P values were calculated based on the Wald χ² test for an interaction term included in a multivariable Cox regression model using the overall study cohort, adjusting for significant baseline covariates with a P value of <.1 that was retained in backward elimination. BMI indicates body mass index (calculated as weight in kilograms divided by height in meters squared); COPD, chronic obstructive pulmonary disease; EF, ejection fraction; PVD, peripheral vascular disease; Renal disease, dialysis, acute, or chronic renal failure, or estimated glomerular filtration rate of less than 60 mL/min/1.73 m².

Figure 4.. Adjusted Relative Risks and Cumulative Incidences of Short-term Outcomes for Multiple Arterial Grafting (MAG) vs Left Internal Thoracic Artery Supplemented by Saphenous Vein Grafts (LITA+SVG)

Adjusted cumulative incidences and relative risks for 30-day mortality, 30-day repeated revascularization, 30-day reoperation for bleeding, and in-hospital postoperative dialysis were estimated by incorporating weights that were obtained from propensity score (PS) weighting from the overall study cohort (LITA+SVG, n = 14496; MAG, n = 5580). Adjusted cumulative incidences and relative risks for 30-day myocardial infarction, stroke, and heart failure were estimated incorporating weights obtained from PS weighting from the Discharge Abstract Database (DAD)-linked study cohort (LITA+SVG, n = 7912; MAG, n = 2633). Adjusted cumulative incidences and relative risks for 30-day and 180-day sternal reconstruction were estimated by incorporating weights that were obtained from PS weighting from a subset of patients in the DAD-linked study cohort who were undergoing CABG from April 1, 2007, to September 30, 2014 (LITA+SVG, n = 7614; MAG, n = 2544). Adjusted relative risks and P values from the χ² tests were calculated by incorporating weights that were obtained from PS weighting.