This publication continues a series of papers devoted to cardiopulmonary diseases and their pathophysiologic basis. The article compares the achievements and traditions of Russian therapeutic school with the principles of Internal Medicine that have evolved in the practice of foreign medical education. The article is devoted to etiology, pathogenesis, clinical manifestations, forms, diagnosis and basic principles of treatment and prevention of the cor pulmonale (pulmonary heart) syndrome. Special attention is paied to pulmonary heart as a complication of COVID-19. The article analyzes the mechanisms and phenomenology of the symptoms important for its differential diagnosis along with original author’s observations and history of medical studies in this field (8 figs, bibliography - 58 refs).