Prognostic Implications of Influenza Virus Infection in a Cardiac Intensive Care Unit: Potential Impact of a Screening Program

OBJECTIVES: Our goal was to determine the presentation and prognosis of influenza in an intensive cardiac care unit and to analyze the impact of an active surveillance program in the diagnosis. METHODS: We performed a prospective registry during the flu season in a coronary unit. In the first phase, no systematic screening was performed. Systematic influenza A and B detection was performed in a second phase for all patients admitted. RESULTS: From 227 patients, we identified 17 (7.5%) with influenza. Influenza patients were more likely to have a non-ischemic cause of admission (14 patients [82.4%] vs. 48 patients [40.3%], p = 0.002), fever (8 patients [47.1%] vs. 3 patients [2.6%], p < 0.001), and respiratory failure (7 patients [41.2%] vs. 8 patients [7%], p = 0.001). Influenza infection was an independent predictor of mortality (odds ratio 12.0, 95% confidence interval 1.9-13.6, p < 0.001). The incidence of influenza was 6.6% (6 patients) when no active screening was performed and 7.9% (11 patients) when systematic detection was performed (p = 0.005). The time to diagnosis was shorter in the systematic screening phase (0.92 ± 1.6 vs. 5.2 ± 3.8 days, p = 0.01). CONCLUSIONS: Influenza affects approximately 8% of patients admitted to an intensive cardiac care unit during the flu season, with a high mortality rate. An active surveillance program improves early detection.