The reactive hyperemia test reveals an alteration in the temporal dynamics of autonomic activity, as reflected by the low-frequency component in heart rate variability analysis, in diabetic patients, suggesting altered autonomic modulation that could serve as an early marker of autonomic dysfunction.
Key Findings
Results
Healthy subjects showed a significant increase in low-frequency (LF) power in heart rate variability immediately after vascular release during reactive hyperemia.
Average latency of LF power increase was 339.64 ± 53.86 ms after vascular release
Average amplitude of LF power increase was 3467.41 ± 2333.68 ms²
Study included 40 age and sex matched healthy subjects as the control group
Recordings were performed at rest and during a reactive hyperemia test consisting of 5-minute arterial occlusion followed by release
Results
Diabetic patients with cardiovascular autonomic neuropathy (CAN) showed a faster but less intense LF power response compared to healthy subjects during reactive hyperemia.
Latency in diabetic patients with CAN was 300.00 ± 20.22 ms, shorter than the 339.64 ± 53.86 ms observed in healthy subjects
Amplitude in diabetic patients with CAN was 907.15 ± 2688.0 ms², substantially lower than the 3467.41 ± 2333.68 ms² in healthy subjects
The response was described as 'faster but less intense' compared to controls
Results
Diabetic patients without CAN showed the lowest LF power response amplitude during reactive hyperemia, with a latency similar to those with CAN.
Latency in diabetic patients without CAN was 300.06 ± 37.64 ms, similar to the CAN group (300.00 ± 20.22 ms)
Amplitude in diabetic patients without CAN was 505.73 ± 489.37 ms², described as 'overall the lowest' among all groups
The study included 35 patients with T2DM without macrovascular complications of diabetes
Methods
Autonomic nervous system function was assessed using both heart rate variability analysis and sympathetic skin response during the reactive hyperemia test.
Electrocardiogram and photoplethysmography recordings were performed at rest and during the reactive hyperemia test
Time-frequency methods were used for heart rate variability analysis
The reactive hyperemia test consisted of a 5-minute arterial occlusion followed by release
Sympathetic skin response was also evaluated as part of autonomic function assessment
Conclusions
The reactive hyperemia test identifies alterations in temporal dynamics of autonomic activity in diabetic patients, suggesting it could serve as an early marker of autonomic dysfunction.
Both diabetic groups (with and without CAN) showed reduced LF power amplitude compared to healthy subjects
Both diabetic groups showed faster LF response latency (~300 ms) compared to healthy controls (~340 ms)
The authors suggest this 'altered autonomic modulation could serve as an early marker of autonomic dysfunction'
Diabetic patients with CAN showed a particularly reactive response pattern
What This Means
This research suggests that a simple test called reactive hyperemia — where blood flow to an arm is temporarily blocked for 5 minutes using a cuff and then released — can reveal important differences in how the nervous system regulates the heart in people with type 2 diabetes. When blood flow is released, the body normally shows a measurable response in heart rate variability that reflects the autonomic (automatic) nervous system kicking in. In healthy people, this response was relatively large and occurred about 340 milliseconds after the cuff was released. In people with diabetes, the response was faster but significantly weaker, regardless of whether they already had a diagnosed nerve condition called cardiovascular autonomic neuropathy (CAN).
Interestingly, diabetic patients without a formal diagnosis of CAN still showed the smallest response amplitude of any group, even smaller than those with CAN. This suggests that subtle changes in how the nervous system controls the heart may occur in diabetes before they are detectable by standard diagnostic tests. The reactive hyperemia test, combined with heart rate variability analysis using time-frequency methods, may therefore capture early autonomic dysfunction that conventional testing misses.
This research suggests that combining the reactive hyperemia test with heart rate variability measurements could be a useful, non-invasive way to detect early signs of nerve damage affecting the cardiovascular system in people with type 2 diabetes. Early detection of such changes could potentially allow for earlier intervention, though further research with larger groups would be needed to confirm these findings and establish clinical usefulness.
López-Galán E, Montoya-Pedrón A, Barrio-Deler R, Suárez-León A, Barzaga-Saborit D, Sánchez-Hechavarría M. (2026). Autonomic cardiovascular changes during reactive hyperemia.. Clinical physiology and functional imaging. https://doi.org/10.1111/cpf.70091