Temporal Changes in Pollen Concentration Predict Short‐Term Clinical Outcomes in Acute Coronary Syndromes

BACKGROUND: Atmospheric changes in pollen concentration may affect human health by triggering various allergic processes. We sought to assess if changes in pollen concentrations were associated with different acute coronary syndrome (ACS) subtype presentations and short‐term clinical outcomes. METHODS AND RESULTS: We analyzed data in consecutive patients presenting with ACS (unstable angina, non–ST‐segment–elevation myocardial infarction, and ST‐segment–elevation myocardial infarction) treated with percutaneous coronary intervention between January 2014 and December 2017 and enrolled in the VCOR (Victorian Cardiac Outcomes Registry). Baseline characteristics were compared among patients exposed to different grass and total pollen concentrations. The primary outcome was occurrence of ACS subtypes and 30‐day major adverse cardiac and cerebrovascular events (composite of mortality, myocardial infarction, stent thrombosis, target vessel revascularization, or stroke). Of 15 379 patients, 7122 (46.3%) presented with ST‐segment–elevation myocardial infarction, 6781 (44.1%) with non–ST‐segment–elevation myocardial infarction, and 1476 (9.6%) with unstable angina. The mean age was 62.5 years, with men comprising 76% of patients. No association was observed between daily or seasonal grass and total pollen concentrations with the frequency of ACS subtype presentation. However, grass and total pollen concentrations in the preceding days (2‐day average for grass pollen and 7‐day average for total pollen) correlated with in‐hospital mortality (odds ratio [OR], 2.17 [95% CI, 1.12–4.21]; P=0.021 and OR, 2.78 [95% CI, 1.00–7.74]; P=0.05), respectively, with a trend of 2‐day grass pollen for 30‐day major adverse cardiac and cerebrovascular events (OR, 1.50 [95% CI, 0.97–2.32]; P=0.066). CONCLUSIONS: Increased pollen concentrations were not associated with differential ACS subtype presentation but were significantly related to in‐hospital mortality following percutaneous coronary intervention, underscoring a potential biologic link between pollen exposure and clinical outcomes.