The overall prevalence of Kounis syndrome (KS) in the United States is 1.1% among patients hospitalized for allergic/hypersensitivity/anaphylactic reactions, with a subsequent 7.0% rate of all-cause inpatient mortality, according to a study published in the International Journal of Cardiology

The nationwide epidemiological data on KS — defined as the concurrence of acute coronary syndrome (ACS) and conditions associated with allergic reactions or hypersensitivity induced by exposure to food, drugs, coronary stents, or other environmental triggers — remains unclear since it was first reported in the United States in 1991. The current cohort study assessed KS prevalence among patients hospitalized for allergic/hypersensitivity/anaphylactic reactions. Using data from the National Inpatient Sample, researchers compared baseline demographics, comorbidities, and KS outcomes for patients hospitalized between 2007 and 2014 for allergic/hypersensitivity/anaphylactic reactions.

In this patient cohort (N=235,420), 2616 patients experienced ACS and were identified as having KS (1.1% overall; 0.2% unstable angina, 0.2% ST-elevation myocardial infarction, and 0.7% non-ST-elevation myocardial infarction). Compared with patients without KS, patients with KS were more often white (71.1% vs 58.6%), older (mean age, 65.9±14.1 vs 57.2±17.8 years), Medicare enrollees (58.9% vs 41.5%), men (46.4% vs 39.9%), and admitted nonelectively (96.8% vs 95.3%; P  <.001 for all).

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Patients with KS had higher hospitalization charges ($52,656 vs $20,487, P <.001), prolonged hospitalization stays (mean, 5.8±6.0 vs 3.0±3.9 days, P <.001), higher rates of all-cause in-hospital mortality (7.0% vs 0.4%, P <.001), and more frequent transfers to other facilities. Patients with KS also showed significantly higher rates of arrhythmias (30.4% vs 12.4%; P <.001), venous thromboembolism (1.6% vs 1.0%; P =.003), and stroke (1.0% vs 0.2%; P <.001), as well as diagnostic and therapeutic coronary interventions (P <.001). Compared with patients without KS, patients with KS had increased odds of in-hospital mortality (unadjusted odds ratio, 18.52 [95% CI, 15.74-21.80; P <.001] and adjusted odds ratio, 9.74 [95% CI, 8.08-11.76; P <.001]).

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Although a precise cause and effect relationship cannot be established using NIS data, these findings do represent the first-ever data on nationwide KS prevalence and in-hospital outcomes. Researchers stated, “The implications of our findings are important for cardiologists to realize the presence of KS even though it’s rare. There are no guidelines or recommended treatments established for KS which makes it complicated to prioritize treatment based on the severity of either by anaphylaxis or acute coronary syndrome. It is also important to find the triggering allergen in case of KS, to avoid such future events.”


Desai R, Parekh T, Patel U, et al. Epidemiology of acute coronary syndrome co-existent with allergic/hypersensitivity/anaphylactic reactions (Kounis syndrome) in the United States: A nationwide inpatient analysis [published online June 8, 2019]. Int J Cardiol. doi:10.1016/j.ijcard.2019.06.002

This article originally appeared on Pulmonology Advisor