The aim of the study is to establish a relationship between baseline myocardial work (MW) assessed by echocardiography and the extent of coronary artery disease (CAD) using SYNTAX score in patients presenting with acute coronary syndrome (ACS) who underwent coronary angiography (CA). SYNTAX score from CA has proven to be a clinically useful anatomical scoring system to assess the burden and complexity of coronary artery disease (CAD). MW is a novel non-invasive measure of cardiac function using echocardiography. Other parameters of cardiac function, such as left ventricular ejection fraction (LVEF) and wall motion score index (WMSI), were also assessed. In this retrospective study, consecutive patients with ACS underwent echocardiography at the presentation to a large, tertiary hospital emergency department from March 2019 to April 2020 were included and analysed. There were 94 patients recruited to the study; age ± 12 years, 62% male. Median Syntax score was 12 (IQR 7–19). All echocardiographic parameters correlated with SYNTAX score. While GLS and MW showed a strong relationship with SYNTAX score (GLS r=0.33, p<0.01; GWW r=0.29, p<0.01; GWE r=0.31, p<0.01), WMSI, a standard assessment in assessing the extent of coronary disease, was a less significant predictor for the complexity of CAD (r=0.22, p=0.03). Baseline assessment of myocardial work correlates better with the extent of coronary disease than standard measures. This assessment may have a role in assisting with the type and timing of coronary intervention in patients presenting with acute coronary syndrome.