A non-invasive diagnostic method in which, under echocardiographic monitoring of the heart, an appropriate saline solution is administered intravenously during a Valsalva maneuver (taking a deep breath and straining). This is used to confirm the presence or absence of a small channel (hole) in the interatrial septum (which serves to prevent the mixing of oxygenated–arterial and deoxygenated–venous blood). This small channel is one of the most common causes of stroke, migraine, and collapse in young and middle-aged individuals. This examination is performed together in combination with a cardiovascular evaluation. 27% of the total population has this small channel from birth, and in some individuals, at a certain period of life, it may lead to adverse events such as stroke, frequent headaches or migraines, collapse, or loss of consciousness.