Patients From More Distressed Communities Are Less Likely to Receive Bilateral Internal Mammary Artery Grafting in a Multi-Institutional Cardiac Surgery Network

T. Rowan. Powley¹, K. Takeda², C. Wang³, P. Wang³, P. Kurlansky^4
1Columbia University Vagelos College of Physicians and Surgeons, Nixa, Missouri ²Columbia university medical center, New York, New York ³Columbia University Vagelos College of Physicians and Surgeons, New York, New York ⁴Columbia University Irving Medical Center, New York, New York

Purpose: The impact of socioeconomic status on the decision to use bilateral internal mammary artery (BIMA)
grafting versus single internal mammary artery (SIMA) grafting in a diverse, multi-institutional cohort
has not been thoroughly investigated. We hypothesized that patients from more distressed communities
would be less likely to receive BIMA grafting.

Methods: Data from patients who underwent CABG in 11 different cardiac surgery programs between 2015 and
2021 were pulled from the Society of Thoracic Surgeons Adult Cardiac Surgery Database. Zip code data
from the database were used to link each patient to a corresponding Distressed Communities Index (DCI)
score, and patients were further divided into DCI quintiles based on the DCI 2016-2020 Full Dataset. The
primary aim was to evaluate the association between DCI and how likely a patient is to receive BIMA
grafting. Secondary outcomes of interest were mortality, combined morbidity and mortality, and deep
sternal wound infection. Mixed effects logistic regression models adjusting for hospital as a random effect
were used. Analyses were stratified by dividing the 11 programs into sites where >40% of CABG
patients received BIMA grafting, sites where 10-40% of CABG patients received BIMA grafting, and
sites where < 10% of CABG patients received BIMA grafting.

Results: A total of 11,892 patients who satisfied the study criteria underwent CABG between 2015 and 2021
(9,611 SIMA patients and 2,281 BIMA patients). In the study population 2,691 (22.6%) patients were
female, and the mean age was 66.4 years (SD=10.01 years). Patients from more distressed communities
were less likely to undergo BIMA grafting than patients from less distressed communities (OR 0.87; 95%
CI, 0.77-0.98, P=0.0187) in the total sample even when adjusting for race. Additionally, women were less likely to
undergo BIMA grafting (OR 0.56; 95% CI, 0.49-0.65; P< 0.001). At sites with >40% BIMA usage,
patients from more distressed communities were less likely to receive BIMA grafting (OR 0.78; 95% CI,
0.64-0.95, P=0.0119). At sites with 10-40% BIMA usage no disparity was observed (OR 0.96; 95% CI,
0.82-1.14, P=0.6634). At sites with < 10% BIMA usage, the disparity was less clear perhaps due to sample
size (OR 0.75; 95% CI, 0.49-1.13, P=0.1636). BIMA patients had lower combined operative and 30-day
mortality (25/2,281 (1.1%) vs. 218/9,611 (2.3%), P=0.0004) but higher rates of superficial sternal wound
infection (33/2,281 (1.4%) vs. 78/9,611 (0.8%), P=0.0046) and deep sternal wound infection (16/2,281
(0.7%) vs. 28/9,611 (0.3%), P=0.0037) compared to SIMA patients.

Conclusion: Patients from more distressed communities are less likely to receive BIMA grafting in a multi-institutional cardiac surgery network. The disparity in patients receiving BIMA grafting could contribute to the poorer outcomes of CABG patients from distressed communities and should be further investigated as a potential area for improvement.

Identify the source of the funding for this research project: NIH T35 Short-Term national Research Service Award