New-onset atrial fibrillation (AF) is a recognized complication of severe sepsis and may be associated with adverse outcomes such as stroke or death. In this month’s issues of the Journal of the American Medical Association, Walkey et al investigated the association of severe sepsis and new-onset AF with the adverse outcomes of in-hospital mortality and in-hospital ischemic stroke.

This study was a retrospective population-based cohort that included patients in the California State Inpatient Database throughout 2007. More than 3 million hospitalized adults were included, of which 1.56% (49,082) had severe sepsis. ICD-9-CM codes were used to identify cases of new-onset AF, severe sepsis, in-hospital ischemic stroke, and risk factors for AF. Multiple sensitivity analyses were conducted to confirm the validity of the ICD-9-CD coding, and to explore the temporality of severe sepsis.

A number of significant results were found in this large cohort study. Overall, new-onset AF was associated with a 7% increase in the adjusted risk of in-hospital death, and 14% of all hospital-associated new-onset AF occurred in the context of severe sepsis (odds ratio [OR] 6.82; 95% confidence interval [CI], 6.54-7.11; P<0.001). In patients with severe sepsis, 2.6% of patients who also had new-onset AF suffered an ischemic stroke, for an average stroke rate of 0.15% per hospital day for patients with new-onset AF. Those with severe sepsis and new-onset AF had a statistically significant greater stroke risk than those with preexisting AF (OR 3.63; 95% CI, 2.51-5.25; P<0.0001). Various risk factors associated with new-onset AF among patients with severe sepsis were identified.

This large observational study is replete with data, and the authors attempted to control for the known limitations involving ICD-9-CD coding. The new-onset AF rate (5.9%) was lower in this study than previously reported rates (6% to 20%), and this may be attributed to the nature of claims data. Furthermore, an immortal-time bias might have falsely lowered the measurable risk for mortality rates associated with new-onset AF. Despite the inherent limitations when using observation data, this study demonstrates significant stroke and mortality risks for patients with severe sepsis and new-onset AF. New-onset AF may be a marker for severity of illness and poor prognosis, or it may directly contribute to mortality. This observational study calls for future investigations to examine the mechanisms responsible for the poor outcomes associated with new-onset AF, as well as possible management options to mitigate the risk for developing AF during severe sepsis.

Concise Critical Appraisal is a regular feature authored by SCCM member Samuel M. Galvagno Jr., DO. Each installment highlights journal articles most relevant to the critical care practitioner.