3-million-patient Medicare analysis suggests pre-existing AFib should be added to risk scores
Pre-existing atrial fibrillation (AF) is linked with adverse outcomes in the 30 days following noncardiac surgery and should, therefore, be added to the revised cardiac risk index (RCRI), according to researchers on a new study including more than 3 million propensity-matched patients.
The study – the largest to date to examine the association between AF and cardiac risk – was published Monday online ahead of the June 28 issue of the Journal of the American College of Cardiology, with authors led by Sameer Prasada, MD, from the Cleveland Clinic.
AF missing from peri-operative risk scoring
AF is an increasingly common cardiac arrhythmia associated with both cardiovascular and cerebrovascular morbidity and mortality, while surgery – including noncardiac – is also associated with major adverse cardiovascular events (MACE).
However, although AF was included in the Goldman pre-operative risk score, it is not currently included as a scored risk factor for major peri-operative cardiac complications in the two most frequently used risk scores for noncardiac surgery: namely, the RCRI and American College of Surgeons National Surgical Quality Improvement Program Surgical Risk Calculator.
The researchers noted that previous studies estimating the effect of AF on peri-operative risk in noncardiac surgeries have shown increased risk in term of cardiovascular outcomes but have been limited by a lack of robust matching between the study groups, subgroup analysis stratified by risk stratification scores and missing studies into the effect of AF on individual hard endpoints.
The current study, therefore, set out to assess the association between pre-existing AF and the risk of early cardiovascular complications after noncardiac surgery in U.S. Medicare beneficiaries undergoing these procedures in the Medicare Provider Analysis and Review File from January 2015 to October 2019.
A total 8,635,758 patients were included in the study cohort. These patients underwent noncardiac surgeries including vascular, thoracic, head and neck, general, genitourinary, orthopedic and neurosurgery, gynecological, breast, and noncardiac transplant. Of these, 1,411,955 (16.4%) had existing AF.
In the total cohort, the mean age was 73.9 years and 55% were women. Pre-propensity score matching, those with existing AF were older (mean age 77.9 vs. 73.1 years; P < 0.001), more likely to be male (54.1% vs. 43.2%; P < 0.001) and white (85.1% vs. 78.8%; P < 0.001), and had higher prevalence of comorbidities including diabetes mellitus, hypertension, heart failure, peripheral arterial disease, chronic lung disease, and chronic kidney disease.
Patients with pre-existing AF were matched with the no pre-existing AF group on exact age, sex, race and ethnicity, and urgency of surgery, type of surgery, CHA2DS2-VASc score, and RCRI index in a 1:2 fashion, resulting in a final 3,054,821 patients (1,131,383 with pre-existing AF and 1,923,438 without) included in the study.
The researchers stratified urgency of the surgery as elective, urgent or emergent, and for patients who underwent more than one surgery in the study period, only the first was included in the analysis. Those younger than 40 years, with less than 3 years of fee-for-service Medicare coverage before noncardiac surgery and those with a history of mitral stenosis were excluded.
AF association with adverse outcomes
The researchers ran propensity-score matching and adjusted for surgery characteristics and patient variables independently associated with higher 30-day mortality risk, including older age; male sex; being Black, Native American or Hispanic; having a higher RCRI score; congestive heart failure; diabetes with complications; lung and liver diseases; end-stage renal disease on dialysis; anemia; paralysis; metastatic disease; and dementia.
After matching, pre-existing AF was independently associated with higher 30-day mortality risk compared to those with no pre-existing AF (8.3% vs. 5.8%; odds ratio [OR]: 1.31; 95% confidence interval [CI]: 1.30-1.32; P < 0.001).
“This association was consistent regardless of sex, race/ethnicity, type of surgery, and whether surgery was elective or urgent,” said the authors.
Pre-existing AF was also independently associated with higher risk of 30-day heart failure (4.44% vs. 2.85%; OR: 1.31; 95% CI: 1.30-1.33; P < 0.001), 30-day stroke (1.70% vs. 1.13%; OR: 1.40; 95% CI: 1.37-1.43; P < 0.001), 30-day systemic embolism (0.07% vs 0.04%; OR: 1.59; 95% CI: 1.43-1.75; P < 0.001), and higher risk of 30-day major bleeding (3.76% vs 3.14%; OR: 1.14; 95% CI: 1.13-1.16; P < 0.001).
However, the researchers found that pre-existing AF carried a lower risk of 30-day myocardial infarction than those without (1.75% vs 1.93%; OR: 0.81; 95% CI: 0.79-0.82; P < 0.001).
The researchers highlighted “multifactorial” mechanisms that likely underline the raised risks associated with AF, including higher prevalence of comorbidities compared with age- and sex-matched controls.
More than 75% of those with AF also receive polypharmacy, while these patients are also susceptible to thromboembolism from left atrial clots, “particularly in patients with anticoagulation interrupted for surgery,” they added.
They also noted: “The atrial fibrosis, loss of atrial and ventricular compliance, and susceptibility to tachycardia increases the risk of fluid overload, and heart and respiratory failure.”
Addition of AF to noncardiac surgical risk scores needed
“Our findings call for incorporating AF as a risk factor in perioperative risk scores for cardiovascular morbidity and mortality,” the researchers concluded. “Further randomized trials are encouraged to confirm our findings.”
In particular, they stressed that adding pre-existing AF to the RCRI score “can improve risk prediction of adverse cardiovascular events after noncardiac surgery.”
In an accompanying editorial, Anne B. Curtis, MD, and Sai Krishna C. Korada, MD, from the University of Buffalo, New York, backed this call, highlighting another recent study by Min Soo Cho, MD, PhD, and colleagues, which found that adding AF to the RCRI “significantly enhanced its discriminating performance.”
“The data presented by Prasada et al. demonstrate improved prediction of adverse postsurgical outcomes after [noncardiac surgery] with the addition of AF to the RCRI compared with currently used risk estimation methods,” the editorialists said.
“Given the correlation of MACE with pre-existing AF, it is time to ‘re-revise’ the RCRI and acknowledge the importance of AF in predicting adverse outcomes after [noncardiac surgery],” they said.
Prasada S, Desai MY, Saad M, et al. Preoperative Atrial Fibrillation and Cardiovascular Outcomes After Noncardiac Surgery. J Am Coll Cardiol 2022;79:2471-2485.
Curtis AB, Korada SKC. Should Atrial Fibrillation Be Included in Preoperative Risk Assessment for Noncardiac Surgery? J Am Coll Cardiol 2022;79:2486-2488.
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