Atrial fibrillation is an independent determinant of mortality and resource utilisation in hospitalised multiple myeloma patients

Background Atrial fibrillation (AF) and multiple myeloma (MM) represent two prevalent chronic diseases with overlapping risk factors in aging populations. However, the clinical significance and outcomes of concurrent AF in MM hospitalizations remain understudied. We aimed to determine the prevalence of AF in hospitalized MM patients and quantify its independent association with in-hospital mortality, length of stay (LOS), and hospital charges. Methods We analyzed 148,030 weighted adult (≥18 years) discharges with principal diagnosis MM from the National Inpatient Sample (2016–2022). The primary outcome was in-hospital mortality. Secondary outcomes were LOS and total hospital charges. Survey-weighted multivariable logistic and linear regression models adjusted for age, sex, race, payer, income, hospital characteristics, admission type, Charlson comorbidity index, and calendar year. Results AF was present in 13.6% of MM hospitalizations (n=20,079 weighted). Compared to MM without AF, patients with AF were older (71.9 vs. 64.5 years; p<0.001) and had higher charlson scores (4.39 vs. 3.60; p<0.001). Crude in-hospital mortality was 8.8% with AF versus 4.1% without AF. In adjusted logistic regression, AF remained independently associated with 86% higher odds of in-hospital mortality (adjusted OR 1.86; 95% CI 1.62–2.14; p<0.001). AF was also independently associated with 1.84 additional hospital days (95% CI 1.45–2.23; p<0.001) and $28,749 higher hospital charges (95% CI $21,158–$36,341; p<0.001) after full adjustment. Conclusion Atrial fibrillation affects one in seven MM hospitalizations and independently confers substantially elevated mortality risk, prolonged LOS, and markedly increased costs, even after controlling for age and comorbidity burden. These findings identify AF as a high-impact cardio-oncologic phenotype in MM and identify the need for integrated cardiovascular risk stratification and management in this population.