Disturbances of blood pressure and spectral heart rate variability during orthostatic stress in patients with type 1 diabetes mellitus

Background : Orthostatic hypotension in diabetes patients is a sign of autonomic dysfunction. Heart rate variability (HRV) analysis is one of the methods for cardiac autonomic neuropathy assessment. The aim of this study was to assess blood pressure and HRV during 5 minute upright tilting in patients with type 1 diabetes. Methods : We studied 48 normotensive diabetes patients aged 18-28 years, with diabetes lasting 9-23 years. Matched control group consisted of 32 healthy persons. We performed 24 h Holter ECG monitoring (SUPRIMA 12, DMS, USA) and ambulatory blood pressure monitoring (Spacelab 90207, Datex-Ohmeda, USA). Manual measurements were initialized every minute during 5 minute standing, preceded by 15 min rest in supine position. Spectral HRV parameters were analyzed: total power (TP), very low frequency (VLF), low frequency (LF) and high frequency (HF) -in 5-min periods in supine and standing position. Results : Systolic blood pressure fall was noted in 19% of diabetes patients and 3% of the controls (p = 0.001) and DBP fall in 23% of diabetes patients and 0% of the controls (p = 0.001). During rest diabetes patients with orthostatic hypotension showed significantly lower TP and VLF spectra (p = 0.001). After tilting lower TP, VLF, LF and HF in diabetes patients with orthostatic hypotension was observed (p = 0.001). In standing position LF (NU, normalized units) decreased in diabetes patients in contrast to healthy people, in which LF spectrum increased. Conclusions : Diabetes patients with orthostatic hypotension have more advanced autonomic dysfunction than diabetes patients without orthostatic hypotension, which manifests as lower spectral HRV components during tilting. Diabetes patients show pathological fall of LF (NU) component during orthostatic stress.