Pre-existing atrial fibrillation and risk of arterial thromboembolism and death in intensive care unit patients: a population-based cohort study.
BACKGROUND
Pre-existing atrial fibrillation (AF) may worsen prognosis in patients admitted to the intensive care unit (ICU).


METHODS
In a cohort study (2005-2011) including all patients with first-time ICU admissions in Denmark (n=57,110), we compared patients with and without pre-existing AF and estimated absolute risks and relative risks (RRs) of arterial thromboembolism and death within 30 days and 365 days following admission, using Kaplan-Meier methods and multivariate regression analyses. We analysed the prognostic impact of AF within strata of patient age, sex, coexisting cardiac diseases, and ICU therapies.


RESULTS
Among ICU patients, 5065 (9%) had pre-existing AF. Compared with patients without AF, those with AF were older (median age 75 vs. 62 years) and had more comorbidity. The risk of arterial thromboembolism was 2.8% in patients with AF and 2.0% in non-AF patients at 30 days, and 4.3% and 2.9%, respectively, at 365 days. Corresponding RRs were 1.41 crude and 1.14 (95% confidence interval [CI] 0.93-1.40) adjusted at 30 days, and 1.50 crude and 1.20 (95% CI 1.02-1.41) adjusted at 365 days. Thirty-day mortality was 27% in patients with pre-existing AF and 16% in non-AF patients (crude RR 1.67, adjusted RR 1.04, 95% CI 0.99-1.10). Corresponding mortality estimates at 365 days were 40.9% and 25.4%, respectively (crude RR 1.61, adjusted RR 1.03, 95% CI 1.00-1.07). In stratified analyses, pre-existing AF increased mortality in ICU patients aged <55 years (adjusted RR at 30 days 1.73, 95% CI 1.29-2.32; adjusted RR at 365 days 1.34, 95% CI 1.06-1.69) and in ICU patients treated with mechanical ventilation (adjusted RR at 30 days 1.12, 95% CI 1.05-1.20, adjusted RR at 365 days 1.09, 95% CI: 1.04-1.15). Analyses stratified by sex and coexisting cardiac diseases yielded adjusted RRs close to 1.


CONCLUSIONS
In ICU patients, pre-existing AF was associated with modestly increased risk of arterial thromboembolism when adjusted for the substantially higher age and comorbidity levels in patients with AF, whereas there was no overall association with mortality. In ICU patients aged <55 years and in those treated with mechanical ventilation, AF predicted increased mortality.
Department of Clinical Epidemiology, Institute of Clinical Medicine, Aarhus University Hospital, Olof Palmes Allé 43-45, DK-8200, Aarhus N, Denmark. jacob.gamst@rn.dk.|Department of Cardiology, Aalborg University Hospital, Hobrovej 18-22, DK-9000, Aalborg, Denmark. jacob.gamst@rn.dk.|Department of Anaesthesia and Intensive Care Medicine, Aalborg University Hospital, Hobrovej 18-22, DK-9000, Aalborg, Denmark. jacob.gamst@rn.dk.|Aalborg Atrial Fibrillation Study Group, Aalborg University Hospital Science and Innovation Centre, Søndre Skovvej 15, DK-9000, Aalborg, Denmark. jacob.gamst@rn.dk.
Jacob
J
Gamst
Department of Clinical Epidemiology, Institute of Clinical Medicine, Aarhus University Hospital, Olof Palmes Allé 43-45, DK-8200, Aarhus N, Denmark. cfc@clin.au.dk.
Christian Fynbo
CF
Christiansen
Department of Anaesthesia and Intensive Care Medicine, Aalborg University Hospital, Hobrovej 18-22, DK-9000, Aalborg, Denmark. bodil.steen.rasmussen@rn.dk.
Bodil Steen
BS
Rasmussen
Aalborg Atrial Fibrillation Study Group, Aalborg University Hospital Science and Innovation Centre, Søndre Skovvej 15, DK-9000, Aalborg, Denmark. lhr@adm.aau.dk.|Faculty of Medicine, Aalborg University, Niels Jernes Vej 10, DK-9220, Aalborg Øst, Denmark. lhr@adm.aau.dk.
Lars Hvilsted
LH
Rasmussen
Department of Clinical Epidemiology, Institute of Clinical Medicine, Aarhus University Hospital, Olof Palmes Allé 43-45, DK-8200, Aarhus N, Denmark. rwt@clin.au.dk.
Reimar Wernich
RW
Thomsen
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000150:complications* / Q000175:diagnosis / Q000401:mortality; D016022:Case-Control Studies; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012044:Regression Analysis; D012307:Risk Factors; D012737:Sex Factors; D013923:Thromboembolism / Q000209:etiology* / Q000401:mortality; D055815:Young Adult