Simple function tests for autonomic neuropathy have a higher predictive value on all-cause mortality in diabetes compared to 24-h heart rate variability.

AIM

To compare the long-term predictive power of heart rate variability (HRV) based on 24 h ECG recordings with a battery of simple autonomic function tests with regard to all-cause mortality in diabetic individuals.

METHODS

240 diabetic persons were randomly selected from the diabetic population. A 24-h ECG was obtained and analysed on the Pathfinder 700. In the RR Tools Program time domain and frequency domain parameters were computed. Five function tests were conducted: Valsalva ratio, heart rate response to standing (30:15 ratio), expiration/inspiration ratio (E/I ratio), orthostatic blood pressure response (Ortho BP), and increase in diastolic blood pressure during sustained handgrip.

RESULTS

178 patients agreed to participate and 136 patients who completed all 5 function tests and had an acceptable ECG recording were included in the analyses. 64 individuals (47%) died during the 15½ year follow-up. Using Cox proportional hazard analyses correcting for age and gender we found that among the HRV parameters only the power in the low frequency band (LF) had an independent predictive value on all-cause mortality (p=0.0002). Multivariate analysis of the five function tests showed that Valsalva (p=0.002), 30:15 ratio (p=0.037), and handgrip (p=0.037) were independent predictors of death. When finally the independent predictors among the function tests and the HRV parameters were assessed in the same model, no significant value could be shown for LF power (p=0.44).

CONCLUSION

The study indicates that simple autonomic function tests are superior to HRV based on 24-h ECG recordings in predicting all-cause mortality in the diabetic population.