Association Between Preexisting Versus Newly Identified Atrial Fibrillation and Outcomes of Patients With Acute Pulmonary Embolism

Background Atrial fibrillation (AF) may exist before or occur early in the course of pulmonary embolism (PE). We determined the PE outcomes based on the presence and timing of AF. Methods and Results Using the data from a multicenter PE registry, we identified 3 groups: (1) those with preexisting AF, (2) patients with new AF within 2 days from acute PE (incident AF), and (3) patients without AF. We assessed the 90‐day and 1‐year risk of mortality and stroke in patients with AF, compared with those without AF (reference group). Among 16 497 patients with PE, 792 had preexisting AF. These patients had increased odds of 90‐day all‐cause (odds ratio [OR], 2.81; 95% CI, 2.33–3.38) and PE‐related mortality (OR, 2.38; 95% CI, 1.37–4.14) and increased 1‐year hazard for ischemic stroke (hazard ratio, 5.48; 95% CI, 3.10–9.69) compared with those without AF. After multivariable adjustment, preexisting AF was associated with significantly increased odds of all‐cause mortality (OR, 1.91; 95% CI, 1.57–2.32) but not PE‐related mortality (OR, 1.50; 95% CI, 0.85–2.66). Among 16 497 patients with PE, 445 developed new incident AF within 2 days of acute PE. Incident AF was associated with increased odds of 90‐day all‐cause (OR, 2.28; 95% CI, 1.75–2.97) and PE‐related (OR, 3.64; 95% CI, 2.01–6.59) mortality but not stroke. Findings were similar in multivariable analyses. Conclusions In patients with acute symptomatic PE, both preexisting AF and incident AF predict adverse clinical outcomes. The type of adverse outcomes may differ depending on the timing of AF onset.