Effect of high altitude polycythemia on heart rate variability, blood pressure rhythm in Tibetan hypertensive patients

Abstract

Objective To explore the impact of high altitude polycythemia(HAPC)on heart rate variability(HRV), blood pressure rhythm in Tibetan patients with hypertension. Methods According to the absence or presence of HAPC with and without essential hypertension(EH), 268 Tibetan patients hospitalized in Qinghai Provincial People's Hospital from January 2012 to December 2016, were divided into three groups: HAPC patients with hypertension(HAPC+ EH group, n=90); HAPC patients without hypertension(HAPC group, n=84); Hypertension without HAPC(EH group, n=94). The general clinical data 24h dynamic ECG and blood pressure monitoring data were collected to evaluate the heart rate variability, blood pressure rhythm and relationship between HAPC and autonomous nerve system. Results The 24-hour standard deviation of the mean normal to normal intervals calculated over a 5-minute period of the entire recording(SDANN)representing sympathetic activity, were significantly higher in HAPC+ EH and HAPC groups than that of EH group(both P<0.05). While, the square root of the mean squared differences of successive normal to normal intervals(rMSSD)representing vague activity, were significantly lower in HAPC+ EH and HAPC groups than that of EH groups(both P<0.05).24-hour mean SBP and DBP in HAPC+ EH group were highest among 3 groups, also patients in HAPC+ EH group had the lowest nocturnal SBP/DBP reduction(all P<0.05). The incidence of non-dipper blood pressure rhythm was raised gradually from EH group, HAPC group, to HAPC+ EH group(38.3%, 59.5%, and 67.8%, respectively). The incidence of non-dipper blood pressure rhythm was significantly higher in HAPC than in EH(both P<0.05). Conclusions HAPC may increase the activity of sympathetic nerve system, decrease the activity of vague nerve system at night, resulting in the decrease of nocturnal SBP/DBP reduction, and increase the incidence of non-dipper hypertension rhythm. Key words: High altitude polycythemia; Hypertension; Heart rate variability; Blood pressure rhythm