New onset atrial fibrillation developing in medical inpatients.

Background: The outcome of patients who develop new onset atrial fibrillation (AF) after admission to an Internal Medicine service for acute medical illnesses is unknown.

Methods: In a retrospective review, we compared patients in the study group: patients who were admitted to hospital for acute medical illnesses and subsequently developed new onset AF during hospitalization, with a control group 1: patients whose admitting diagnosis was new onset AF and a control group 2: patients who were admitted for acute medical illnesses and never developed AF. We analyzed clinical characteristics and all-cause mortality rate during the first 30 days, 6 months, and 1 year after admission.

Results: The 1-year mortality rates in study group were significantly higher than control group 1 (62% versus 8%, P < 0.001) and control group 2 (62% versus 29%, P < 0.05). These results suggest that AF and acute medical illness both are risk factors for increased mortality. The odds ratios were 4.05 (P = 0.023) and 18.33 (P = 0.001) for AF and acute medical illnesses, respectively, indicating that acute medical illness is the better predictor for mortality. Troponin I levels were elevated in 46% of patients in study group versus 12% in control group 1 and 42% in control group 2 (P < 0.05).

Conclusions: Medical inpatients who develop new onset AF during hospitalization for acute medical illnesses have an increased mortality when compared with patients who were admitted solely for new onset AF. Acute medical illness rather than AF plays a more important role on the increased mortality in this subset of patient population.