Background: Myocardial infarction (MI) with no obstructive coronary arteries (MINOCA) is a special form of the acute coronary syndrome. The heterogeneous pathophysiology of MINOCA is not well elucidated and includes cardiac and non-cardiac causes. Slow flow phenomenon on coronary angiography can be associated with several possible causes of MINOCA confirmed by optical coherence tomography (OCT). Therefore, the aim of this study is to assess the underlying mechanism of the delayed washout phenomenon on coronary angiography and the potential role of subintimal coronary artery dissection (SD) in the setting of an acute MI. Methods and design: This clinical prospective, descriptive research will enroll patients diagnosed with acute MI (STEMI or NSTEMI) identified by coronary angiography, followed by OCT imaging of the coronary arteries at the Emergency Clinical County Hospital of Târgu Mureș, Romania. The enrolled patients will be separated into two groups based on OCT examination, patients with SD and patients with no SD. Conclusion: The underlying mechanisms of MINOCA with delayed washout phenomenon on coronary angiography is still poorly understood. Modern invasive imaging techniques are capable to assess the microstructure of the coronary artery wall and are able to offer the much needed information to elucidate the pathophysiological changes which ultimately cause the acute event. The current study offers a new, complex – clinical, invasive and noninvasive imaging, as well as biomarker-based – approach, which may lead to a better understanding and treatment of this pathology.