Use Of Single Internal Mammary Artery Research Articles

STS Adult Cardiac Surgery Database: 2021 Update on Outcomes, Quality, and Research

The Society of Thoracic Surgeons Adult Cardiac Surgery Database is the most mature and comprehensive cardiac surgery database. It has been the foundation for quality measurement and improvement activities in cardiac surgery, facilitated the generation of accurate risk adjusted performance benchmarks and serves as a platform for novel research. Recent enhancements have added to the database's functionality, ease of use, and value to multiple stakeholders. This report is the sixth in a series of annual reports that provide updated volumes, outcomes, database-related developments, quality improvement initiatives, and research summaries using the Adult Cardiac Surgery Database in the past year.

Short-Term Risk of Bilateral Internal Mammary Artery Grafting in Diabetic Patients

This study compares the morbidity and mortality at 30 days following the use of bilateral internal mammary arteries (BIMA) vs a single internal mammary artery (SIMA) at the time of coronary artery bypass grafting (CABG) in patients with a preoperative HbA1c. Patients undergoing CABG from January 2008 to December 2016 reported to the Society of Thoracic Surgeons database were retrospectively reviewed. The patients were divided into 2 groups: use of BIMA or use of SIMA and propensity matched. To assess the effect of preoperative HbA1c, both groups were further divided into 5 subgroups: patients without diabetes mellitus (DM), or patients with DM and a preoperative HbA1c level in one of four groups (< 7%, 7-9%, 9-11%, or >11%). The postoperative outcomes in both the BIMA and SIMA groups were compared. There were 700,504 and 28,115 patients with measured preoperative HbA1c levels in the SIMA and BIMA groups, respectively. Propensity score matching identified 23,635 comparable patients in each group for analysis. There was no difference in postoperative mortality between the BIMA and SIMA groups (1.3% vs 1.2%). The incidences of sternal wound infection (SWI) in patients undergoing placement of BIMA vs SIMA were: 0.8% vs 0.4% with no DM (P < 0.0001), 1.9% vs 1.0% with HbA1c < 7% (P < 0.001), 2.4% vs 1.2% with HbA1c 7-9% (P < 0.001), 2.8% vs 1.4% with HbA1c 9-11% (P = 0.02), 4.1% vs 1.5% with HbA1c > 11% (P = 0.01). Based on the incidence of SWI, BIMA is a reasonable approach with an HbA1c<7%.

Abstract 171: User Beware: Understanding the Adjusted Estimates of Propensity Score Methods

Background: Propensity score methods are used in observational studies to compensate for the lack of random allocation by balancing measured baseline characteristics between treated and untreated patients. Yet default implementations of propensity score methods may lead to contradictory findings. Our goal was to illustrate differences in treatment effect estimates produced using propensity score methods such as matching and inverse probability weighting (IPW). Methods: We used data from a retrospective analysis of the Northern New England Cardiovascular Disease Study Group registry that studied reintervention after single internal mammary artery (SIMA) versus bilateral internal mammary artery (BIMA) conduit use in 41,481 coronary artery bypass grafting (CABG) procedures from 1992-2014. Results: The mean duration of follow-up was 13.2 (IQR: 7.4-17.7) years. In our standard multivariable Cox regression analysis, the adjusted HR for reintervention was 0.83 (95% confidence interval (CI): 0.75-0.92) in patients receiving BIMA compared to SIMA (Table). The 1:1 propensity matched analysis (HR=0.79, 95% CI: 0.69-0.91) and IPW estimate among the treated (HR=0.83, 95% CI: 0.75-0.92) show a similar protective treatment effect of BIMA use on reintervention. However, the IPW approach for the overall population effect unusually showed no difference between BIMA and SIMA on reintervention-free survival (HR=1.08, 95% CI: 0.94-1.24). Conclusions and Relevance: The adjusted HR for reintervention after BIMA versus SIMA use in CABG was remarkably different for the two IPW estimates. This difference is attributed to the population represented by the two IPW approaches- the IPW among the treated estimate represents the effect in the average study population, whereas the IPW in the treated represents the effect in the treated population alone. Determining how the study population is balanced (weighted to look like the overall study population versus treated group) is a large driver of treatment effect, and a key element of propensity score methods. Ultimately, the treatment effect estimate desired should drive the choice of propensity score adjustment method.

Bilateral Versus Single Internal Mammary Artery Use in Coronary Artery Bypass Grafting: A Propensity Matched Analysis

Bilateral internal mammary artery (BIMA) grafts have demonstrated superior long-term outcomes compared with single internal mammary artery (SIMA) grafts. Despite this, BIMA remains widely underutilised due to perceived technical challenges and concerns regarding wound healing. We sought to examine the morbidity and mortality associated with BIMA use in a propensity-matched cohort of patients. From 2009 to 2016, 3,594 consecutive patients underwent coronary artery bypass surgery at three affiliated institutions. Thirty-day (30) mortality and morbidity data were collected prospectively. Propensity-score matched analyses were performed for BIMA versus SIMA use controlling for a number of preoperative characteristics. Overall, 29% of procedures were performed off pump, with a greater proportion in the BIMA group (43% vs. 21%, p<0.001). In the propensity-score analysis consisting of 820 matched pairs, there were similar rates of 30-day mortality (1.3% BIMA vs. 0.9% SIMA, p=0.48) and deep sternal wound infection (1.1% BIMA vs. 0.9% SIMA, p=0.84). The rate of superficial sternal wound infection trended towards being higher in the BIMA group (2.6% vs. 1.3%, p=0.077). The rates of red blood cell transfusions (27.4% vs. 27%, p=0.217), other blood product transfusions (18% vs. 20%, p=0.217), and reoperation for bleeding (2.9% vs. 2.1%, p=0.349) were similar. Bilateral internal mammary artery use was associated with similar rates of deep sternal wound infection compared to SIMA use, with a preponderance of superficial sternal wound infections that did not result in increased mortality or transfusion requirements. The use of BIMA should be more widely considered for coronary artery bypass surgery.

National Trends and Geographic Variation in Bilateral Internal Mammary Artery Use in the United States

The goal of this study was to characterize the adoption rate and regional variation in bilateral internal mammary artery (BIMA) use during coronary artery bypass grafting (CABG) in the United States. Observational study of 100% sample of fee-for-service Medicare beneficiaries aged 65 years or older, continuously enrolled in Parts A and B from 2009 to 2014 (n= 162,860,439). Rates of beneficiaries receiving a BIMA versus single internal mammary artery (SIMA) during CABG are expressed per 1,000 beneficiaries and aggregated by Hospital Referral Region (HRR). An HRR is a validated unit for quantifying regional variation in health care. The absolute national rate of BIMA use declined during the study period from 0.21 claims per 1,000 beneficiaries in 2009 to 0.13 in 2014 (p < 0.001). When indexed to overall CABG volume, no change was seen in the frequency of BIMA use over time (p= 0.883). SIMA use ranged from 1.3 to 8.5 claims per 1,000 Medicare beneficiaries, whereas BIMA use ranged from 0 to 1.5 (p < 0.001). A significant correlation was found between regional volume of SIMA use and likelihood of BIMA use (correlation coefficient 0.673, p < 0.001). Although both SIMA and BIMA use correlated with regional volume of diagnostic cardiac catheterization, the correlation was stronger for SIMA use (correlation coefficient 0.962 versus 0.682, p < 0.001). Over the past 5 years, no growth was seen in BIMA use among Medicare beneficiaries, and the frequency of BIMA use during CABG remained low. There was significant regional variation in BIMA use, however, which demonstrates opportunity for continued growth of BIMA grafting.

Bilateral Internal Mammary Artery Use Can Be Safely Taught Without Increasing Morbidity or Mortality

Evidence shows a likely survival benefit with the use of bilateral internal mammary arteries (BIMA) compared with a single internal mammary artery (SIMA). Nonetheless, BIMA use is often not used or taught because of a perceived increase in operative time and complexity. This study aimed to evaluate operative time, morbidity, and mortality in both resident and nonresident cases using BIMA compared with SIMA. Consecutive patients undergoing isolated coronary artery bypass grafting (October 2012 to April 2015) at a single institution were reviewed. Cases were stratified on the basis of the use of SIMA versus BIMA and resident teaching versus nonresident teaching cases. Primary outcomes included operative time, postoperative morbidity, and mortality. A total of 416 patients were identified; 335 of 416 (81%) patients received a SIMA, and 81 of 416 (19%) patients received BIMA. A total of 184 of 416 (44%) were resident cases: 143 of the 335 (43%) SIMA cases and 41 of the 81 (51%) BIMA cases. Use of BIMA in resident cases was associated with a longer operative and cardiopulmonary bypass (CPB) time than resident SIMA cases, but this increased time did not affect morbidity or mortality. Use of SIMA versus BIMA in nonresident cases had no significant difference on total operative time, CPB time, postoperative morbidity, or mortality. Overall, operative and 1-year mortality rates were similar in the SIMA and BIMA groups (SIMA: 1.2%, 1.8%, respectively; BIMA: 0%, 0%, respectively; p= NS). In the hands of an experienced surgeon, BIMA use can be effectively performed without an increase in operative or CPB time. In resident teaching cases, BIMA use may increase operative time, but it can be safely taught without affecting morbidity or mortality.

Abstract 15732: Impact of Bilateral Mammary Artery Grafting for Coronary Revascularization in the Obese Population, a Retrospective Study

Context: The prevalence of obesity has increased over the last decade. Although bilateral internal mammary artery (BIMA) grafting for coronary revascularization is associated with better survival in the general population, it is also a risk factor for deep sternal wound infection (DSWI), a complication more frequently seen in the obese population. The aim of this study is to determine the short and long-term outcomes of the use of BIMA in obese patients undergoing cardiac surgery, assessing the impact on survival and the incidence of DSWI. Methodology: This is a single center retrospective cohort study with prospectively collected data. We included obese patients (BMI ≥ 30 kg/m2) undergoing coronary artery bypass grafting (CABG) between April 1991 and April 2014 in our institution. Propensity score matching was conducted for the entire population studied. Results: Results showed that 5608 obese patients underwent CABG during the study period. After propensity scoring, 494 patients receiving BIMA revascularization were matched to 5089 patients receiving single internal mammary artery (SIMA) revascularization. All pre-operative characteristics were comparable except for a higher prevalence of heart failure in the SIMA group. In-hospital post-operative mortality in the two groups was comparable (1.0% BIMA vs 1.8% SIMA, p=0.86). In-hospital DSWI was also comparable (1.2% BIMA vs 1.0% SIMA, p=0.63). However total DSWI (including post-discharge DSWI, median time 19 days) was significantly higher in the BIMA group compared to the SIMA group (3.6% vs 2.2%; p&lt;0.0001). Over a median follow-up of 7.2 years (mean follow-up 7.7 ± 4.2 years), there was no observed long-term survival advantage in the BIMA vs the SIMA group (p=0.22). Conclusion: Using BIMA instead of SIMA increases the risk of DSWI in obese patients. The use of BIMA is not associated with better survival compared to the use of SIMA in this population. These results suggest that the increased short-term risk of post-operative infection associated with BIMA revascularization is not offset by a long-term survival benefit. Given the increased risk of DSWI and absence of mid- to long-term survival benefit, caution should be exerted when selecting the use of BIMA grafting in the obese population.

LONGTERM RECURRENT ISCHEMIC CARDIOVASCULAR EVENTS AMONG PATIENTS WITH ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION: INSIGHTS FROM THE AMI-QUÉBEC REGISTRY

RESULTS: Results showed that 5608 obese patients underwent CABG during the study period. After propensity scoring, 494 patients receiving BIMA revascularization were matched to 5089 patients receiving single internal mammary artery (SIMA) revascularization. All pre-operative characteristics were comparable except for a higher prevalence of heart failure in the SIMA group. In-hospital post-operative mortality in the two groups was comparable (1.0% BIMA vs 1.8% SIMA, p1⁄40.86). In-hospital DSWI was also comparable (1.2% BIMA vs 1.0% SIMA, p1⁄40.63). However total DSWI (including post-discharge DSWI, median time 19 days) was significantly higher in the BIMA group compared to the SIMA group (3.6% vs 2.2%; p<0.0001). Over a median follow-up of 7.2 years (mean follow-up 7.7 4.2 years), there was no observed longterm survival advantage in the BIMA vs the SIMA group (p1⁄40.22). CONCLUSION: Using BIMA instead of SIMA increases the risk of DSWI in obese patients. The use of BIMA is not associated with better survival compared to the use of SIMA in this population. These results suggest that the increased short-term risk of post-operative infection associated with BIMA revascularization is not offset by a long-term survival benefit. Given the increased risk of DSWI and absence of midto long-term survival benefit, caution should be exerted when selecting the use of BIMA grafting in the obese population.

Bilateral versus single internal mammary coronary artery bypass grafting in Sweden from 1997-2008.

BackgroundPrior observational studies have suggested better outcomes in patients who receive bilateral internal mammary arteries (BIMA) during coronary artery bypass grafting (CABG) compared with patients who receive a single internal mammary artery (SIMA). The aim of this study was to analyze the association between BIMA use and long-term survival in patients who underwent primary isolated CABG.Methods and ResultsPatients who underwent primary isolated non-emergent CABG in Sweden between 1997 and 2008 were identified. The SWEDEHEART registry and other national Swedish registers were used to acquire information about patient characteristics and outcomes. Unadjusted and multivariable adjusted regression models were used to estimate the association between BIMA use and early mortality, long-term survival, and a composite of death from any cause or rehospitalization for myocardial infarction, heart failure, or stroke in the overall cohort and in a propensity score-matched cohort. The study population consisted of 49702 patients who underwent CABG with at least one internal mammary artery, and 559 (1%) of those had BIMA grafting. In the adjusted analyses, BIMA use was not associated with better survival compared with SIMA use in the overall cohort (hazard ratio (HR) for death: 1.16, 95% confidence interval (CI): 0.97 to 1.37) or in the matched cohort (HR: 1.04, 95% CI: 0.78 to 1.40). The results were similar for early mortality and the composite endpoint. Reoperation for sternal wound complications was more common among BIMA patients (odds ratio: 1.71, 95% CI: 1.01 to 2.88).ConclusionsBIMA grafting was performed infrequently and was not associated with better outcomes compared with SIMA grafting in patients undergoing non-emergent primary isolated CABG in Sweden during 1997–2008.

Prevalence and variability of internal mammary graft use in contemporary multivessel coronary artery bypass graft

To assess the current status of the prevalence and variability of internal mammary graft use in contemporary multivessel coronary artery bypass graft (CABG). The internal mammary artery (IMA) is considered the gold-standard conduit in coronary artery bypass graft (CABG) surgery. There is universal agreement that the IMA graft is associated with significantly improved short-term and long-term survival in CABG and the use of the IMA is recognized as a key performance measure world wide. In the recently developed Society of Thoracic Surgeons (STS) composite measure for CABG, use of an IMA was found to be the only intra-operative performance measure associated with quality of care. Furthermore, several studies have shown that bilateral IMA (BIMA) use improves long-term outcome compared with single IMA use. An objective assessment of surgical quality is essential to improve surgical outcomes. There is strong evidence that IMA graft use is associated with significantly improved short-term and long-term survival in CABG. In spite of this, the prevalence of IMA grafting is less than expected. Moreover, there is a large variability in IMA use by hospital. There are also disparities in IMA use by sex and race, which should be addressed in the interest of expanding the benefits of IMA grafting to the maximum possible number of patients. Although the frequency of IMA use in CABG procedures seems to increase each year, further actions are necessary at the individual clinician, institutional, and political levels to improve quality of care.