Short-term and prospective epidemiological surveys conducted in Highlanders of the Tien Shan and Pamirs (2800-4200 m above the sea level) have shown that the chronic high-altitude pulmonary heart (CHAPH) is a common type of pathology, with growing age of the examinees the frequency of CHAPH being considerably on a decrease. CHAPH is characterized by a progressive course and is frequently complicated by various types of cardiac arrhythmia. With a growing degree of marked right ventricular hypertrophy the number of lethal outcomes among Highlanders increases.