Relationship between ambient temperature and frequency and severity of cardiovascular emergencies: A prospective observational study based on out-of-hospital care data.

Objective: To test the hypothesis that more cardiovascular emergencies occur at low rather than at high temperatures under moderate climatic conditions.

Methods: This was a prospective observational study performed in a prehospital setting. Data from the Emergency Medical Service in Hamburg (Germany) and from the local weather station were evaluated over a 5-year period. Temperature data were matched with the associated rescue mission data. Lowess-Regression analysis was performed to assess the relationship between the temperature and the frequency of individual cardiovascular emergencies. In addition, three threshold-temperatures (0°C, 10°C, 20°C) were defined in order to determine the frequency of cardiovascular emergencies above and below each cut-off value. The severity of emergencies was assessed using the National Advisory Committee for Aeronautics (NACA) scoring system.

Results: A total of 35,390 cardiovascular emergencies were treated by Emergency Physicians. Transient Loss of Consciousness increased at high temperatures (above 20°C): +43% (95%-CI: [27%; 59%]). In contrast, Coronary Artery Disease +26% (95%-CI: [17%; 34%]), Cardiac Pulmonary Edema +21% (95%-CI: [14%; 27%]), Hypertensive Urgency +18% (95%-CI: [10%; 25%]) and Cerebrovascular Accident +17% (95%-CI: [8%; 24%]) increased at low temperatures, particularly below 10°C (significance level for all: p<0.001). No temperature-related effect was seen in Cardiac Arrhythmia and Pulmonary Embolism and no significant correlation was found between the severity of emergencies and temperature.

Conclusions: Our findings suggest that some cardiovascular emergencies such as Coronary Artery Disease, Cardiac Pulmonary Edema, Hypertensive Urgency and Cerebrovascular Accident are more frequent in low temperatures even under mild climatic conditions.