Association of Preexisting Atrial Fibrillation or Flutter With 30-Day Outcomes After Septic Shock: A Propensity-Matched Federated Database Study.

Preexisting atrial fibrillation (AF) or atrial flutter may impair cardiovascular reserve during septic shock, potentially leading to worse clinical outcomes; however, its independent association with short-term outcomes remains uncertain. Using the TriNetX U.S. Collaborative Network, we identified adults with septic shock and compared patients with preexisting AF/flutter, documented at least 1 month before the index event, with those without prior AF/flutter. Clinical outcomes were compared after 1:1 propensity score matching for demographic characteristics, comorbidities, and baseline cardiovascular medication use. Outcomes included 30-day all-cause mortality, cerebral infarction, renal replacement therapy, invasive mechanical ventilation, acute-care utilization, and vasopressor/inotrope use. Effect estimates were reported as relative risks (RRs) with 95% confidence intervals. After propensity score matching, 76,295 patients were included in each cohort. Preexisting AF/flutter was associated with significantly higher risks of all-cause mortality (RR 1.07, 95% CI, 1.06-1.09; P<0.001), renal replacement therapy (RR 1.30, 95% CI, 1.25-1.35; P<0.001), invasive mechanical ventilation (RR 1.14, 95% CI, 1.12-1.16; P<0.001), acute-care utilization (RR 1.06, 95% CI, 1.05-1.06; P<0.001), and vasopressor/inotrope use (RR 1.09, 95% CI, 1.08-1.10; P<0.001). There was no significant difference in cerebral infarction (RR 1.11, 95% CI, 1.00-1.24; P=0.054). Among patients with septic shock, preexisting AF/flutter was associated with higher mortality and greater use of organ-supportive therapies, including renal replacement therapy, invasive mechanical ventilation, and vasopressor/inotrope use, but not with a significant increase in cerebral infarction. Preexisting AF/flutter may serve as an important prognostic marker for early risk stratification in septic shock.