Pollen exposure before ACS hospitalization may negatively affect PCI outcomes
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Although researchers could not associate pollen exposure with incident ACS, they did observe elevated in-hospital mortality after PCI following days of high pollen exposure prior to presentation.
In a publication in the Journal of the American Heart Association, researchers reported that high exposure to grass pollen concentration in the 7 days preceding hospitalization for ACS was associated with increased in-hospital mortality after PCI.
“The link between exposure to environmental pollutants, such as particulate matter and poor cardiovascular outcomes, is well documented,” Omar Al-Mukhtar, MBChB, of the department of cardiology at Western Health in Melbourne, Australia, and colleagues wrote. “However, there is a paucity of data linking pollen grain exposure and cardiovascular outcomes. We therefore aimed to evaluate the relationship between exposure to pollen grains and the frequency of different ACS subtype presentations and short-term clinical outcomes. Identification of such a relationship would have important public health implications pertaining to public health policies and defining susceptible populations during vulnerable climatic periods.”
For the present study, researchers utilized data from the Victorian Cardiac Outcomes Registry to identify consecutive patients who presented with ACS from 2014 to 2017 and underwent PCI (n = 15,379; mean age, 63 years; 76% men). The primary outcomes were any ACS and 30-day MACCE, defined as mortality, MI, stent thrombosis, target vessel revascularization or stroke. The proportion of ACS subtypes was 9.6% for unstable angina, 44.1% for non-STEMI and 46.3% for STEMI.
Pollen exposure and CV risk
Data on pollen concentration during this time were obtained from the Melbourne Pollen registry operated by the University of Melbourne, which records daily grass and total pollen concentrations during peak grass pollen season.
Researchers observed no differences in mean daily (10.5 vs. 10.5; P = .8) or monthly ACS presentations (281.9 vs. 317.6; P = .11) during peak grass pollen seasons compared with nonpeak seasons, respectively.
Additionally, prevalence of in-hospital mortality (3.5% vs. 3.6%; P = .75) and 30-day MACCE (6.5% vs. 7.3%; P = .11) were similar between peak grass pollen seasons and nonpeak grass pollen seasons, respectively.
Pollen exposure leading up to hospitalization
Researchers then evaluated the effect of pollen exposure during the days preceding hospitalization and found that high exposure to grass pollen concentration in the 2 days prior to ACS presentation was associated with increased in-hospital mortality (OR = 2.17; 95% CI, 1.12-4.21; P = .021) and a trend toward increased risk for 30-day MACCE (OR = 1.5; 95% CI, 0.97-2.32; P = .066).
Moreover, high exposure to grass pollen concentration in the 7 days preceding hospitalization was associated with in-hospital mortality (OR = 2.78; 95% CI, 1-7.74; P = .05), but not 30-day MACCE (OR = 1.4; 95% CI, 0.81-2.41; P = .23).
“Because we do not have any information on the allergy status of the cohort on which our analysis was based, we must currently assume that the effect of grass and total pollen is relevant for the entire population,” the researchers wrote. “Nevertheless, these data raise the possibility of a biological link between allergen exposure with adverse clinical outcomes following the development of acute cardiovascular illness, as suggested by other studies.
“A possible explanation of pre-ACS exposure to pollen grains and subsequent in-hospital mortality is the development of heightened inflammatory response adversely impacting different organ function, thereby leading to a clinical adverse event,” the researchers wrote. “Increased inflammation is a hallmark of ACS, and raised inflammatory markers in patients with ACS treated with PCI were associated with increased risk of poor cardiovascular outcomes. The precise mechanisms underpinning inflammation to adverse cardiovascular outcomes remains to be elucidated.”
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