Is air pollution associated with increased incidence of myocardial infarction and cardiogenic shock?

By Dr. Sushama R. Chaphalkar, PhD.Reviewed by Lily Ramsey, LLMMar 4 2024

In a recent study published in Scientific Reports, researchers from Korea explored the association between prolonged exposure to air pollution (AP) and ST-elevation myocardial infarction (STEMI) and in-hospital cardiogenic shock.

They found that exposure to particulate matter (PM) with diameter <10 µm (PM₁₀) was associated with an elevated risk of STEMI compared to non-STEMI (NSTEMI).

Further, exposure to PM₁₀ and sulfur dioxide (SO₂) exposure were found to be associated with an increased incidence of in-hospital cardiogenic shock.

Study: Long-term air pollution exposure is associated with higher incidence of ST-elevation myocardial infarction and in-hospital cardiogenic shock. Image Credit: TR STOK/Shutterstock.com

Background

Ischemic heart diseases (IHD), such as acute myocardial infarction (AMI), present a significant health challenge across the globe, particularly in the Asia-Pacific region.

Evidence suggests that short- and long-term exposure to AP is associated with complications in individuals with coronary artery disease (CAD), such as hospitalization, re-admission, and early death.

Although previous studies have explored the short-term impact of AP on AMI, there is limited investigation into the long-term outcomes, specifically regarding the relative occurrences of STEMI and NSTEMI, and the development of cardiogenic shock.

While STEMI typically involves total coronary artery blockage and active heart muscle damage, NSTEMI involves partial blockage with lesser heart muscle damage.

Previously, researchers found that AP exposure was linked to adverse clinical outcomes in AMI patients, in both short and long-term exposures.

In the present study, the same group of researchers build on their previous findings to investigate the potential link between long-term AP exposure, STEMI, and cardiogenic shock.

About the study

The study included participants from the Korea AMI registry (KAMIR) and KAMIR-National Institutes of Health (NIH), involving a nationwide prospective multicenter registration series to establish treatment guidelines and analyze Korean AMI patients' clinical characteristics.

The participants were enrolled from 2006 to 2015. The exclusion criteria for patients were symptom-onset before 2006, missing onset date, age < 18 years, and the absence of a diagnosis of myocardial infarction (MI) at discharge. A total of 45,619 participants were included— 20,526 with NSTEMI and 25,093 with STEMI.

Hourly AP concentrations obtained from the Korean Ministry of Environment were measured at 329 nationwide monitoring stations using various methods.

Data transformation into daily averages and calculation of annual averages before the symptom day were performed, excluding PM2.5 due to unavailability. The date of onset of MI symptoms was defined as the symptom date.

AMI diagnosis involved elevated cardiac biomarkers, typical electrocardiogram (ECG) changes, and clinical symptoms, with STEMI identified by new ST-elevation ≥ 1 mm in ≥ 2 contiguous leads.

NSTEMI patients exhibited positive biomarkers without STEMI ECG findings. Cardiogenic shock was defined by low blood pressure, requiring support to maintain it, and signs of pulmonary congestion. Its complication was considered if it occurred post-admission.

Information on various cardiovascular risk factors (diabetes mellitus, family history of CAD, hypertension, dyslipidemia, prior cardiovascular disease, heart failure, prior cerebrovascular disease (CVA), and smoking) was self-reported by the patients.

Statistical analysis involved the use of chi-square test, Fisher’s exact test, Student’s t-test, Mann–Whitney rank test, Kolmogorov-Smirnov test, generalized logistic mixed effect models, correlation analysis, variance inflation factor, odds ratios (OR), logistic regression, and subgroup analysis.

Results and discussion

Compared to NSTEMI patients, STEMI patients were younger, predominantly male, had higher smoking rates, fewer underlying chronic conditions, and presented with more severe angiographic and clinical features, including a higher rate of cardiogenic shock complications during the index hospitalization.

PM₁₀ showed a significant association with increased STEMI incidence (OR 1.009), and both PM₁₀ and SO₂ were linked to higher risks of in-hospital cardiogenic shock complications (OR 1.03 and 1.104, respectively).

Conversely, increase in O₃ was negatively correlated with cardiogenic shock (OR 0.891). Subgroup analysis showed a significant association between a decrease in STEMI incidence and an increase in NO₂ among CVA patients.

The study emphasizes the role of minimizing exposure to elevated AP levels in reducing MI risk and mortality across high and low-risk groups.

However, the findings are limited by the study design, limited sampling data for PM_2.5, restricting associations with clinical events, lack of PM_2.5 data for years preceding 2015, potential misclassification of patient exposure, and the potential for variations and input errors in the multicenter registry data, emphasizing the need for cautious interpretation.

Conclusion

In conclusion, the present study suggests that elevated concentrations of air pollutants, especially PM₁₀, pose an environmental risk and are linked to an increased occurrence of STEMI.

Additionally, both PM₁₀ and SO₂ levels are identified as risk factors for the complication of in-hospital cardiogenic shock following MI.

The findings highlight the urgent need for implementing policy-level strategies and clinical interventions to mitigate AP exposure, potentially preventing STEMI and reducing the risk of severe cardiovascular complications for improved public health outcomes.