Background: Echocardiography is a central method for non-invasive assessment of cardiac function. Ejection fraction (EF) measured by Simpson´s biplane method is the most established method for quantifying left ventricular pump function, while global longitudinal strain (GLS) is a more modern method that measures myocardial deformation. Both methods evaluate systolic function but are based on different physiological principles and can be influenced by the observer´s experience and measurement technique.  

Aim: The aim of the study was to compare correlation, reproducibility and measurement uncertainty between ejection fraction (EF) and global longitudinal strain (GLS) in healthy individuals and examining the inter-observer variability between two inexperienced observers. 

Method: The study was conducted as a quantitative observational study with 25 healthy participants aged 18-49. Two independent observers performed image acquisition and analysis using the Siemens ACUSON SC2000 ultrasound system. Statistical analysis included Pearson´s correlation coefficient (r), Intraclass Correlation Coefficient (ICC), Bland-Altman analysis and coefficient of variation (CV).  

Results: The results showed a strong negative correlation between EF and GLS  (r = -0,67; p < 0,001). Inter-observer variation showed moderate to strong correlation for both EF (r = 0,58) and GLS (r = 0,56). EF exhibited a non-significant bias of 0,2 % and a CV of 5,4 %. For GLS, a significant bias of –1,4 % and a CV of 15,3 % were observed. Analysis over time showed that observer agreement improved during the study, particularly for GLS measurements. 

Conclusion: The study demonstrates a strong correlation between EF and GLS, but as the methods measure different aspects of left ventricular function, they should be considered complementary rather than interchangeable. EF showed lower measurement uncertainty than GLS when used by inexperienced observers, but the precision of GLS seems to improve with increased practical experience.