Extreme Heat Exposure and Acute Cardiovascular Events in Pakistan: Clinical Risk, Multisystem Complications and Health-System Resilience

Abstract

Background: Extreme heat represents a growing challenge for cardiovascular health and health systems in climate-vulnerable regions. This study investigated the associations between ambient heat exposure, acute cardiovascular presentations, clinical outcomes, and hospital operational performance at tertiary cardiovascular centers in Pakistan.

Methods: This multicenter retrospective hospital-based observational study included 13,392 cardiovascular presentations over 552 hospital-days in Karachi, Lahore, and Peshawar. The primary exposure was daily maximum temperature, with extreme heat defined by center-specific 95th-percentile thresholds. Negative binomial regression was used to assess daily presentation counts, and multivariable logistic regression evaluated patient-level outcomes.

Results: Thirty-eight hospital-days met the extreme-heat criterion, accounting for 1,018 presentations. Each 5°C increase in same-day maximum temperature was associated with increased daily cardiovascular presentation rates (IRR 1.14, 95% CI 1.09–1.20; P<.001). Higher temperatures were also associated with acute kidney injury (AOR 1.28), multiorgan dysfunction (AOR 1.38), CCU/ICU admission (AOR 1.16), mechanical ventilation (AOR 1.26), and in-hospital mortality (AOR 1.27). Extreme-heat periods were characterized by higher occupancy and longer door-to-balloon times, while median length of stay remained unchanged. Sensitivity analyses confirmed the consistency of the hospital-day association.

Conclusion: Higher ambient temperatures were associated with increased cardiovascular burden, greater clinical severity, and heightened hospital service pressure in Pakistan. These findings support the need for heat-adaptive cardiovascular preparedness and ongoing multi-year investigation.