One in five older adults will develop an infection up to six months after heart surgery – and women, in particular, have a 60% chance of developing one, two studies suggest.
Led by Michigan Medicine, researchers examined thousands of cases involving Medicare beneficiaries who’d had coronary artery bypass grafting, also known as CABG or heart bypass, or aortic valve replacement.
Women had 60% greater odds of developing postoperative infections, the three most common being urinary tract, pneumonia and sepsis, according to the reports, posted in MedicalXpress.
Black patients also had higher rates of overall infection (28%) than white patients (19.2%).
The studies are published in The Journal of Thoracic and Cardiovascular Surgery.
“Our investigations highlight persistent disparities in outcomes for patients undergoing cardiac surgery that will require multidisciplinary efforts to correct,” said J’undra Pegues, MD, MS, first author of the study on infection disparities and a T32 research fellow in the Department of Cardiac Surgery at University of Michigan Health.
In one of the studies, which covered hospitals across Michigan, 21.2% of Medicare beneficiaries developed an infection up to six months after surgery.
Pneumonia and UTIs accounted for nearly 17% of all infections, and rates of infection varied nearly 40% across hospitals.
“Tracking infections beyond the short time horizon is important, as some hospitals are better equipped than others to prevent infections, and some patients face disproportionate challenges given social determinants of health,” Pegues said.
Several past studies have uncovered lower rates of infection after these procedures.
The higher numbers found in the two current studies, investigators say, are more than likely due to the longer follow-up period of six months.
“Patients who have a heart bypass or valve replacement surgery are at risk for developing other infections that may come about over a longer period, like UTIs and gastrointestinal infections,” said Donald Likosky, PhD, senior author of both studies and Richard and Norma Sarns Research Professor of Cardiac Surgery at the University of Michigan Medical School.
Most national registries neither track these additional infections nor conduct surveillance beyond 30 days after the procedure, said Charles Schwartz, MD, chair of the Department of Surgery at Trinity Health Oakland and co-author on both studies.
“This probably results in a vast underestimation of the burden of infections after cardiac surgery,” he added.
Heart bypass and aortic valve replacement account for more than half of all cardiac surgical procedures in Michigan. Nationwide, CABG accounts more than 70% of all heart surgeries.
In one of the Michigan studies, patients receiving their operation at lower performing hospitals, with higher expected rates of infection, were more likely to be discharged to extended care or rehabilitation facilities.
“The findings highlight that patients are at risk for developing infections early and late after their cardiac surgical procedure,” said co-author of both studies Francis Pagani, MD, PhD, the Otto Gago MD Endowed Professor in Cardiac Surgery at UM Medical School and associate director of the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative.
“Other age-related health conditions, such as diabetes, high blood pressure and cancer, may contribute to later-occurring infections identified in this study.”
Likosky’s study team notes that collaborative learning efforts between healthcare systems are needed to reduce disparities in patient outcomes.
Through a statewide quality improvement intervention spanning 2012 to 2017, hospitals that adopted infection prevention strategies were able to lower the risk of pneumonia relative to the rest of the country.
“Our study reinforces the importance of bringing together hospitals and community stakeholders to identify and subsequently implement potentially modifiable hospital and community practices to prevent postoperative infections,” said Syed Sikandar Raza, MD, first author and integrated thoracic surgery resident at University of Michigan Health.
Study 1 details
Interhospital variability in 180-day infections following cardiac surgery
Syed Sikandar Raza et al
Published in Journal of Thoracic and Cardiovascular Surgery on 10 January 2025
Abstract
Objective
To evaluate hospital-level variation in infections following cardiac surgery and develop and evaluate a 180-day infection quality metric.
Methods
This study evaluated Medicare claims that were merged with institutional Society of Thoracic Surgeons Adult Cardiac Surgery Database files among patients undergoing cardiac surgery across 33 Michigan centres. The primary outcome was infection occurring within 180 days of surgery. Adjusted institutional infection rates were estimated using logistic regression with robust variance estimation. Terciles of observed/expected ratios were created to assess interhospital variability in infections and associated morbidity and mortality.
Results
A total of 5 466 operations were evaluated. The average patient age was 71.1 ± 7.8 years, 29.5% of the patients were female, and 4.8% were black. The infection rate was 21.2% overall and higher among females. Infection was associated with lower left ventricular ejection fraction, diabetes, severe chronic lung disease, cerebrovascular disease, and urgent operations (P < .0001 for all). The most common infection was pneumonia (8.5%). Adjusted infection rates varied 39.5% across hospitals (range, 7.2%-46.7%). Patients treated in hospitals in the highest tercile of observed/expected infection ratio had a higher rate of associated discharge to extended care/rehabilitation (27.9% vs 24.7%, P < .0001) but comparable stroke and mortality risk compared to patients treated in hospitals in the lowest tercile.
Conclusions
One in 5 Medicare beneficiaries develop a 180-day infection following cardiac surgery, with rates varying 39.5% across hospitals. Patients at higher versus lower O:E tercile hospitals were more commonly discharged to extended care/rehabilitation settings, although rates of stroke and mortality were equivalent in the two groups. Collaborative learning interventions may be warranted to advance the observed variability in 180-day infections.
Study 2 details
Disparities in 180-day infection rates following coronary artery bypass grafting and aortic valve replacement
J’undra N. Pegues et al
Published in JTCVS on 15 January 2025
Abstract
Objective
The study objective was to compare sex and racial differences in 180-day infection rates after coronary artery bypass grafting and aortic valve replacement.
Methods
A statewide Society of Thoracic Surgeons Adult Cardiac Surgery Database was linked to Medicare claims data to identify 8 887 beneficiaries undergoing coronary artery bypass grafting and aortic valve replacement (surgical or transcatheter) between 2017 and 2021. The primary outcome was the incidence of 180-day infection. Secondary outcomes included 10 infection subtypes. Multivariable logistic regression was used to evaluate the relationship between sex and race (black vs non-black) and infections. Two secondary analyses were conducted: (1) robustness of the primary analysis after excluding urinary tract infections given established sex-related differences and (2) testing a sex∗race interaction.
Results
The mean (SD) age of the cohort was 74.5 (8.9) years, with 36.9% female and 4.2% black. The infection rate was 19.6%, although this varied by patient sex (female vs male: 23.7% vs 17.1%) and race (black vs non-black: 28.0% vs 19.2%), both P less than .0001. Differences in infection rates for female patients were driven by urinary tract infections and pneumonia for black patients. Risk-adjusted odds of infection were 1.6-fold significantly higher among female patients but non-significant for black patients. A sex∗race interaction was present, with non-black female patients versus non-black male patients having a 1.63 higher odds of infection.
Conclusions
This multicentre study identified a 1.6-fold higher odds of infection among female patients. Non-black female versus male patients had a 63% higher odds of infection. Transdisciplinary collaborative learning interventions should be considered to address these known disparities in infection rates.
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