P-165: Incidence, risk factors and impact of supraventricular tachycardia (SVT) with high dose therapy melphalan among myeloma patients undergoing autologous stem cell transplant (HDT/ASCT)

Introduction: High dose therapy melphalan followed by autologous stem cell transplant (HDT/ASCT) confers an overall survival (OS) advantage and is the mainstay of frontline therapy among transplant-eligible myeloma patients. Melphalan is an arrhythmogenic chemotherapy but the incidence of developing peri-transplant supraventricular tachycardia (SVT) and its impact on OS has not been well described. We performed a single institutional analysis of 2970 patients undergoing HDT/ASCT from 2000-2021 to evaluate the incidence, risk factors and the long-term impact of SVT during the peri-transplant period.

Methods: Variables of interest were extracted from Clinical Data Warehouse (CDW), a Structured Query Language (SQL) database as approved by Emory Institutional Review Board (IRB). A tiered algorithmic approach was developed to automate the extraction of data elements from the CDW utilizing SQL scripts which were validated by data from manual extraction and existing data from myeloma database and the transplant database. Broad tiered criteria included EKG obtained peri-transplant, anti-arrhythmic drug, ICU transfer, and cardiology consultation.

Results: Of the 2970 patients, 614 (20.7%) underwent transplant between 2000-2010 and 445 (15%) were above the age of 70. Median age of transplant was 61.6 years, 48% had ≥ very good partial response (≥VGPR) pre-transplant, 59.6% had hypertension (HTN), 28.7% had coronary artery disease (CAD), 12.2% had prior β-blocker usage and 10.7% had prior arrhythmia. 948 (31.9%) had an EKG during the peri transplant period. 203 (6.8%) developed SVT and 155 (5.2%) required transfer to ICU. The median age of patients that developed SVT was higher (62.88 vs 60.8 years, p< 0.01) and length of stay (LOS) was increased by a day for patients that had SVT peri-transplant (16 vs 15 days, p< 0.001). Risk factors for developing SVT include HTN: 66.5% vs 56.4%, p< 0.001, CAD: 35.3% vs 25.6%, p< 0.001, β-blockers: 15.5% vs 10.6%, p< 0.001, arrhythmias: 15.9% vs 8.2%, p< 0.001, age ≥70: 18.4% vs 13.4%, p< 0.001. 30-day readmit rate was 8.5% (SVT vs no SVT: 11.9% vs 6.9%, p< 0.001), 30 day mortality was 0.8% (SVT vs no SVT: 2.4% vs 0.1%, p< 0.001), 100 day mortality was 2% (SVT vs no SVT: 4.4% vs 0.8%, p< 0.001). The OS was 9 years (SVT vs no SVT: 9.3 vs 6.6 years, p< 0.001). This difference extended to patients transplanted between 2011-2021 where the OS was 10.5 years (SVT vs no SVT: 10.82 vs 6.53, p< 0.001). H/o β-blocker use was the only independent risk factor for shortened OS (HR 1.25 95% CI (1.029-1.52), p=0.025).

Conclusions: While the data aligns with known findings of melphalan as an arrhythmogenic agent, the current data identifies prior h/o β-blocker use as an independent risk factor for shortened OS. SVT peri-transplant resulted in longer hospital LOS, significantly increased 30-day mortality and 100-day mortality and had an impact on OS. The current data supports preventive strategies aimed at decreasing the incidence of SVT peri-transplant.