Combination of cardiorespiratory reflex parameters and heart rate variability power spectrum analysis for early diagnosis of diabetic cardiac autonomic neuropathy

Abstract

Aim The study objective was to compare cardiorespiratory reflex (CR-R) parameters and heart rate variability power spectrum (HRV-PS) analysis in the diagnosis of cardiac autonomic neuropathy (CAN) in diabetic patients. Methods Four CR-R tests (Valsalva manoeuvre, deep breathing, and two successive 5-minute periods with the subject supine and standing, respectively) were performed in 399 diabetic patients (58.6% male, median age: 51 years) and 105 healthy controls (40% male, median age: 34 years). Patients with two or more abnormal CR-R parameters were classified as CAN+, while those with only one abnormal CR-R parameter were considered CAN ‘borderline’. HRV-PS was performed in all study participants. Results The low-frequency (LF) area with the patient standing was reduced in CAN+ diabetics (median 35.6 normalized units [nu], n = 31), in CAN ‘borderline’ diabetics (median 64.3 nu, n = 70) and even in diabetics without CAN (median 89.4 nu, n = 298) versus control subjects (median 93.7 nu; P < 0.001, P < 0.001 and P < 0.05, respectively). Adding the abnormal (< 2.5 nu) LF area to the diagnostic criteria in CAN ‘borderline’ patients caused 11 (15.7%) patients to be considered CAN+. Conclusion Combining abnormal CR-R parameters (I – E and I/E the most specific) with HRV-PS (particularly the LF area with the subject standing) allowed diagnosis of diabetic CAN at an earlier stage.