The Prevalence of ST-Segment Depression on Ambulatory Electrocardiographic Monitoring During Daily Life in High-Risk Asymptomatic Police Officers

BACKGROUND: In individuals with no known ischaemic heart disease, the prevalence and significance of ST-segment depression on ambulatory electrocardiographic monitoring is unclear. We therefore determined the prevalence of ST-segment depression among middle-aged male police officers, an occupational group in whom an increased risk of ischaemic heart disease has been reported, who also had multiple individual coronary risk factors but no known ischaemic heart disease. METHODS: Full-time male police offices aged 45 years or more with at least two coronary risk factors but no known ischaemic heart disease performed a 24h ambulatory electrocardiographic monitor, timed to include a shift of work. The number and duration of episodes of ST-segment depression were determined. In those in whom ST-segment depression was detected, exercise thallium scintigraphy and repeat 24h ambulatory electrocardiographic monitoring were performed. RESULTS: The prevalence of ST-segment depression on 24h ambulatory electrocardiographic monitoring, including an 8h period of normal work, was 3.4% (95% confidence interval 1.3-8.3%). Exercise thallium scintigraphy was carried out in those in whom ST-segment depression had been detected. Despite two participants developing ST-segment depression during exercise, no evidence of myocardial ischaemia was observed on the perfusion scan. Therefore, the prevalence of ST-segment depression on ambulatory electrocardiographic monitoring in this asymptomatic but high-risk population was low and, when it did occur, no exercise-induced myocardial ischaemia was observed. CONCLUSION: These results suggest that ST-segment depression on ambulatory electrocardiographic monitoring in asymptomatic subjects may not represent myocardial ischaemia. The use of this parameter to screen asymptomatic populations for ischaemic heart disease is therefore highly questionable.