Retrospective cohort analysis of heart rate variability in patients with high altitude pulmonary hypertension in Tibet

BACKGROUND: Studies from both humans and animals experiments have offered abundant evidence supporting that mountain sickness is associated with changes in autonomic nervous function (ANF), which can be measured by heart rate variability (HRV). HYPOTHESIS: We aimed to assess changes of ANF in chronic mountain disease by measuring HRV in patients with high altitude pulmonary hypertension (HAPH). METHODS: From November 2018 to March 2019, 120 patients in the cardiac care unit of the People's Hospital of Tibet Autonomous Region were selected as the observation group, and 50 patients without organic heart disease served as the control group. Pulmonary artery systolic pressure was evaluated by echocardiography in patients with HAPH, divided into three groups: mild (30‐49 mm Hg), moderate (50‐69 mm Hg) and severity (≥70 mm Hg) groups. A 24‐hour dynamic electrocardiogram (DCG) was obtained for each patient. HRV (SDNN, SDANN, RMSSD, PNN50, and HRVTI for time domain; TP, VLF, LF, HF, and LF/HF for frequency domain) indexes were measured and compared. RESULTS: Compared with the control group, time domain parameters including SDNN, SDANN, RMSSD, PNN50, and HRVTI were reduced, as well as frequency domain indexes such as TP, VLF, LF, and HF. LF/HF was highest in mild HAPH group and lowest in the moderate HAPH group, and the difference between the two groups was statistically significant. CONCLUSIONS: The HRV of patients with chronic HAPH in high altitude areas in Tibet is significantly reduced relative to healthy controls, and significantly negatively correlated with the severity of pulmonary artery hypertension.