Abstract 4364346: Risk of Hospitalization in Patients with Heart Failure Exposed to Extreme Heat and Poor Air Quality in the Western United States

Introduction: Patients with underlying cardiovascular (CV) disease are vulnerable to adverse health events related to extreme weather. Limited data exist in those with heart failure (HF). In the western U.S., where heat waves and wildfire exposure are common, understanding the impact of heat on HF–related outcomes is critical for prevention and clinical management. Research Question/Hypothesis: We examined the risk of hospitalizations and emergency room (ER) visits associated with short-term exposure to extreme heat and poor air quality in HF patients stratified by HF type. Methods: Using 2021 Medicare data, we identified patients with HF before January 1, 2021, residing in 11 western U.S. states (Arizona, California, Colorado, Idaho, Montana, New Mexico, Nevada, Oregon, Utah, Washington, and Wyoming). The primary outcomes included all-cause, CV, and HF-related hospitalizations and ER visits. A case-crossover design was used, with case days defined as the event date and control days matched by day of the week within the same month. Patients were stratified based on HF type and identified on inpatient or outpatient diagnoses prior to the case day. Conditional logistic regression was applied to estimate odds ratios (ORs) for outcomes associated with extreme heat exposure, defined as daily maximum temperature above the 85th percentile of the local decadal average, adjusting for airborne particulate matter (PM 2.5. ) levels and public holidays. Results: We identified 43,447 HF patients (mean age 73 ±16 years) of whom 9,676 had HF with reduced ejection fraction (HFrEF) and 13,093 HF with preserved ejection fraction (HFpEF). Only extreme heat exposure was associated with a 6% increased odds for all-cause hospitalization (OR 1.06; 95% CI: 1.02,1.10); 10% increase in all-cause ER visits (OR:1.10; 95% CI 1.06-1.15); and 8% increase CV-related ER visits (OR 1.08; 95% CI: 1.00–1.17). These effects were demonstrated primarily in HFpEF and not HFrEF (Table). Conclusion: Short-term extreme heat exposure but not poor air quality was associated with an increased risk of hospitalization and ER visits in HF patients residing in the Western US, especially in those with HFpEF. This heightened vulnerability may be due to impaired thermoregulation and reduced cardiovascular adaptability in those with HFpEF