**1. Introduction**

Congenital heart diseases (CHD) are highly variable, ranging from simple to complex lesions. Therefore, pediatric echocardiography faces different challenges, especially in demonstrating complex anatomy and assessing myocardial function in ventricles with variable morphology [1]. At the same time, there is a desire to detect early changes in ventricular function in cardiac patients as well as in patients with systemic diseases potentially affecting the heart. Furthermore, bedside techniques are increasingly used in clinical medicine, which is also seen in pediatric echocardiography. Consequently, the development of new methods or the upgrade of existing ultrasound techniques is urgently needed.

Recent advances in pediatric echocardiography include functional imaging, myocardial deformation imaging, and 3D echocardiography. Advances in ultrasound techniques, especially in pediatric probes, allow imaging with high temporal and

spatial resolution, which opens a new perspective on the mechanics and function of the myocardium. 3D echocardiography can help understand complex anatomy with associated functional changes, which is valuable for appropriate intervention planning. For pediatric cardiac patients, a highly variable ventricular morphology is typical, therefore, assessment of myocardial function may be challenging, especially assessment of right ventricular function and function of a single ventricle. Deformation imaging with strain and strain-rate quantification enables quantitative assessment of myocardial function independent of underlying morphology [1, 2]. Strain imaging also enables detecting minimal changes in the global and regional systolic function of the ventricles and allows recognition of the preclinical stage of different diseases affecting the heart [3].

Functional echocardiography has become increasingly useful in everyday clinical practice; nowadays it plays a central role in understanding and managing hemodynamics in critically ill patients [4]. Functional echocardiography facilitates real-time evaluation of cardiac performance, identifying the nature of cardiovascular compromise, guiding therapeutic decisions, and monitoring response to treatment [5]. Namely, early detection of cardiac dysfunction may help to choose an appropriate inotropic or vasopressor support. Good collaboration with pediatric cardiologists taking care of the patient is essential in the performance and interpretation of functional echocardiography [6].
