Low HRV better predictor of CV outcomes than tests of CAN in diabetes patients

Type 2 diabetes patients are at higher risk of cardiovascular disease and all-cause mortality than non-diabetic individuals. CAN is a common and severe complication independently associated with increased mortality, all-cause mortality, and cardiovascular morbidity in diabetics. In the initial stages, CAN may be asymptomatic and non-diagnosed, and changes in HRV may be the only findings.

Previous studies using HRV parameters or Ewing's clinical tests have shown increased cardiovascular and mortality risks linked with CAN in diabetes patients. However, few studies have examined clinical tests of cardiovascular autonomic neuropathy and heart rate variability as predictors for adverse outcomes. Also, no previous study investigated whether CAN markers improved risk discrimination for these negative outcomes.

Against the above background, Claudia R.L Cardoso and colleagues from Brazil aimed to determine whether tests for CAN and 24-hour HRV could improve the prediction for outcomes in type 2 diabetes.

For this purpose, 541 patients with type 2 diabetes performed tests for CAN. A subsample comprising 313 patients had 24-hour HRV (standard deviation of the averaged regular RR intervals for all 5 min segments [SDANN] and the standard deviation of all regular RR intervals [SDNN]).

The associations between CAN/low HRV with cardiovascular events and all-cause mortality were examined. The improvement in risk discrimination of CAN/HRV addition was tested by the Integrated Discrimination Improvement (IDI) index and C-statistics.

The authors reported the following findings:

• 25% had CAN, and 17-18% had low HRV, respectively, by SDANN-SDNN.
• Over a median follow-up of 12 years, there were 177 CVEs and 236 all-cause deaths in the whole cohort and 96 CVEs and 129 all-cause deaths in the subsample.
• CAN is linked with 40% excess risks of CVEs/all-cause mortality, and low HRV was associated with 2-fold higher risks of outcomes.
• HRV improved risk discrimination for CVEs/mortality with increases in C-statistics up to 0.039 and IDIs up to 25%.

"Findings from the long-term prospective cohort study in middle-aged people with type 2 diabetes showed that both clinical tests of CAN and low HRV were predictors of mortality and cardiovascular outcomes," the authors wrote. "However, concerning improvement in risk discrimination, HRV parameters were better than clinical tests."

"Clinical tests of CAN did not improve risk discrimination for any of the outcomes, except for a modest 7% improvement in IDI for risk of all-cause mortality," they concluded.

Reference:

The study titled "Prognostic Importance of Cardiovascular Autonomic Neuropathy on Cardiovascular and Mortality Outcomes in Individuals with Type 2 Diabetes: The Rio de Janeiro Type 2 Diabetes Cohort" was published in Diabetes Research and Clinical Practice. DOI: https://doi.org/10.1016/j.diabres.2022.110232