Preexisting cardiovascular disease and inpatient arrhythmias after autologous stem cell transplantation for multiple myeloma: a National Inpatient Sample analysis.

BACKGROUND: Autologous stem cell transplantation (ASCT) remains the standard for transplant-eligible multiple myeloma (MM) patients. However, data on inpatient arrhythmias among MM-ASCT hospitalizations with preexisting cardiovascular disease (CVD) remain limited. We evaluated present-on-admission (POA)-coded new-onset inpatient arrhythmias according to preexisting CVD status. METHODS: We analyzed the unweighted National Inpatient Sample (2016-2022) and identified adult MM-ASCT hospitalizations with valid POA indicators. Preexisting CVD included coronary artery disease, atrial fibrillation, valvular disease, conduction disorders, congestive heart failure, and prior cardiac arrest. The primary outcome was POA-coded new-onset inpatient arrhythmia. Secondary outcomes included length of stay, hospital charges, and discharge disposition. Firth's penalized logistic regression was used for sparse events, with LASSO regression performed as an exploratory sensitivity analysis. RESULTS: Among 58 MM-ASCT hospitalizations, 12 (21%) had preexisting CVD. New-onset inpatient arrhythmias occurred in 9 hospitalizations (16%) and were more frequent with preexisting CVD (66.7% vs 2.2%, P < 0.001). No clear differences were observed in length of stay, charges, or discharge disposition. CONCLUSIONS: New-onset inpatient arrhythmias were more frequent among MM-ASCT hospitalizations with preexisting CVD. These findings are hypothesis-generating and warrant validation in larger clinically adjudicated cohorts.