Abstract
We evaluated 24 hour power spectral analysis (PSA) patterns of heart rate variations (HRV) in type 2 diabetic patients with orthostatic hypotension (OH). We studied 91 type 2 diabetic patients (44 women, 47 men). HRV was determined automatically every 5 min over 24 h using a Holter electrocardiographic recording. Power spectral analysis of RR intervals was by fast Fourier transformation. Low-frequency (LF; both sympathetic and parasympathetic activity), high-frequency (HF; pure parasympathetic activity), and the ratio of LF to HF, an index of sympathovagal balance, were used as indices of cardiac autonomic activity. PSA was evaluated every 3 hours during 24 h. Eighteen patients had OH (17%). We divided diabetic patients into those with no OH (n=77) and with OH (n=14). Those with OH had lower renal function than those with no OH. The prevalence of hypertension was higher in those with OH. The LF/HF ratio was significantly lower in diabetic patients with OH. We found no significant difference in HF between groups. Multivariate analysis disclosed that the 24 h mean LF/HF ratio was an independent factor for postural fall in systolic blood pressure. In conclusion, the pathogenesis of OH was associated strongly with impairment of cardiac sympathetic function in patients with type 2 diabetes.
