Demographic Characteristics Affect 30-Day CABG Hospital Readmission Rates

coronary artery bypass grafting
The researchers’ goals included quantifying and examining unplanned readmissions within 30 days of CABG surgery, including their causes and associated factors.

Hospital readmissions are common within 30 days of coronary artery bypass graft (CABG), with the majority of patients readmitted for noncardiac causes influenced by demographic and clinical patient characteristics. This is according to research results published in the Journal of Cardiothoracic Surgery.

Researchers sought to quantify the rates of unplanned hospital readmission within 30 days of CABG surgery, evaluate how readmission rates vary by study-level characteristics, explore the underlying causes of unplanned hospital readmission, and evaluate the associations of patient and hospital-level factors associated with readmission.

In a systematic review and meta-analysis, researchers identified 1506 relevant studies, 53 of which were included for review. Of these studies, 40 were conducted in the US; most were based on administrative data while 22 used medical records. Studies varied in sample size.

Most participants were men (range, 65% to 99%) and the mean age at CABG ranged from 57 to 76 years. In studies with reported comorbidities, diabetes and hypertension were the most common; 22 studies included only patients who underwent isolated CABG procedures.

On an individual study level, 30-day readmission rates following CABG ranged from 12.9% to 23.3%. Pooled 30-day readmission was 12.9%. Significant evidence showed between-subgroup heterogeneity in terms of pooled 30-day readmission rates by data source: 14.5% for administrative data and 10.6% for medical record data. Rates also varied when grouped by publication year, country, study quality, and proportion of elective procedure, but no statistically significant between-subgroup differences were noted.

The causes of 30-day readmission after CABG were reported in 23 studies. Cardiac causes — including congestive heart failure and arrhythmia — accounted for 10% to 40% of all readmissions; between 6.9% and 28.6% of all 30-day readmissions were due to infection and sepsis. Other common causes included pleural effusion, respiratory complications, thromboembolic disorders, and gastrointestinal complications.

Estimated pooled odds ratio [OR] per 10-year increase in age was 1.12 in 11 studies. Women and non-White race (pooled OR, 1.29 and 1.15) were also associated with higher readmission risk. Patients with US Medicare or Medicaid were more likely to be readmitted than those with private insurance (pooled OR, 1.39).

A meta-analysis included studies on the relationship of 12 comorbid conditions with readmission rate following CABG. These complications included diabetes, hypertension, heart failure, myocardial infarction, atrial fibrillation, stroke, peripheral vascular disease, renal disease, pulmonary disease, liver disease, immunosuppression, and obesity. All comorbidities except hypertension were significantly associated with 30-day readmission following CABG. Pooled ORs for 30-day readmission were highest for immunosuppression, renal disease, and atrial fibrillation (1.45, 1.41, and 1.33).

On a hospital level, meta-analyses were not performed due to “either differences in comparison groups or limited numbers of studies examining any specific association,” per the researchers. A total of 8 studies evaluated the association with hospital CABG volume, and 5 of them found that lower hospital CABG volume was significantly associated with higher rates of readmission. When examining surgeon CABG volume, 1 study reported an OR of 1.16 comparing surgeons performing 100 or fewer cases vs more than 100 cases.

Study limitations include a high level of heterogeneity between studies, a lack of examination of the role of procedural factors, limitations typical of administrative database use, and variability in “diligence and accuracy” of administrative data collection.

“A significant proportion of patients undergoing CABG require readmission within 30 days and the majority of these are readmitted for noncardiac causes,” according to the researchers, who added, “30-day readmission rates are strongly influenced by patients’ demographic and clinical characteristics, but not broadly defined hospital characteristics.”

“The findings of this study are valuable for benchmarking quality improvement in clinical care as well as informing hospital readmission reduction policies for CABG,” they concluded.


Shawon MSR, Odutola M, Falster MO, Jorm LR. Patient and hospital factors associated with 30-day readmissions after coronary artery bypass graft (CABG) surgery: a systematic review and meta-analysis. J Cardiothorac Surg. 2021;16(1):172. doi:10.1186/s13019-021-01556-1