Introduction Throughout recent years the demand for prehospital emergency care has increased significantly. Non-traumatic chest pain is one of the most frequent complaints. Our aim was to investigate the trend in frequency of the most urgent ambulance patients with chest pain, subsequent acute myocardial infarction (AMI) diagnoses, and 48-hour and 30-day mortality of both groups. Methods Population-based historic cohort study in the North Denmark Region during 2012–2018 including chest pain patients transported to hospital by highest urgency level ambulance following a 1-1-2 emergency call. Primary diagnoses (ICD-10) were retrieved from the regional Patient Administrative System, and descriptive statistics (distribution, frequency) performed. We evaluated time trends using linear regression, and mortality (48 hours and 30 days) was assessed by the Kaplan Meier estimator. Results We included 18,971 chest pain patients, 33.9% (n = 6,430) were diagnosed with”Diseases of the circulatory system” followed by the non-specific R- (n = 5,288, 27.8%) and Z-diagnoses (n = 3,634; 19.2%). AMI was diagnosed in 1,967 patients (10.4%), most were non-ST-elevation AMI (39.7%). Frequency of chest pain patients and AMI increased 255 and 22 patients per year respectively, whereas the AMI proportion remained statistically stable, with a tendency towards a decrease in the last years. Mortality at 48 hours and day 30 in chest pain patients was 0.7% (95% CI 0.5% to 0.8%) and 2.4% (95% CI 2.1% to 2.6%). Conclusions The frequency of chest pain patients brought to hospital during 2012–2018 increased. One-tenth were diagnosed with AMI, and the proportion of AMI patients was stable. Almost 1 in of 4 high urgency level ambulances was sent to chest pain patients. Only 1 of 10 patients with chest pain had AMI, and overall mortality was low. Thus, monitoring the number of chest pain patients and AMI diagnoses should be considered to evaluate ambulance utilisation and triage.