[Block of the anterior median branch of the bundle of His].

Present-day data (histological, electrocardiographic, vectorcardiographic and coronarographic) are presented in the paper, forming the concept of quadrifascicular structure of the conduction system of the heart. The criteria are indicated, on which the diagnostics of blocking of anterior-medial ramification of the left branch of His bundle is based. The author presents 4 of his own observations, illustrating the variety of the manifestations of the blocking of the anterior-medial ramulus--intermittent blocking, combination with blocking of anterior-upper ramulus, blocking in the presence of only septal fibres of the ramulus and blocking with spreading of the fibres also in the anterior-septal region of the left ventricle of heart.